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From the start of 2016, the journal uses article numbers instead of page numbers to identify articles. If you are required to add page numbers to a citation, you can do with using a colon in the format [article number]:1–[last page], e.g. 10:1–20.

Polymers, Volume 8, Issue 8 (August 2016) – 42 articles

Cover Story (view full-size image): The cover image visualizes a method to determine the strength of the proximity effect in multiphoton micro-printing. To this end, foci pairs with various separations are obtained by spatial light modulation. These foci patterns are then used for simultaneous polymerization of line pairs. Knowing the separation of the foci, perpendicular and along the writing direction, allows for the mutual influence of the line pairs to be mapped spatially and temporally. From these spatio-temporal maps of the proximity strength, conclusions on the underlying mechanism may be drawn. By Erik Hagen Waller. View this paper.
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3542 KiB  
Communication
Hedgehog Buckyball: A High-Symmetry Complete Polyhedral Oligomeric Silsesquioxane (POSS)
by Yu Hu, You Wang, Hong You and Di Wang
Polymers 2016, 8(8), 315; https://doi.org/10.3390/polym8080315 - 22 Aug 2016
Cited by 5 | Viewed by 5291
Abstract
In this study, we report UV-MALDI-TOF MS evidence of a fullerene-like silsesquioxane, a high-symmetry polyhedral oligomeric silsesquioxane (POSS or SSO) formulated as R60-Si60O90 or T60 (T = RSiO1.5). The T60 preparation can be performed [...] Read more.
In this study, we report UV-MALDI-TOF MS evidence of a fullerene-like silsesquioxane, a high-symmetry polyhedral oligomeric silsesquioxane (POSS or SSO) formulated as R60-Si60O90 or T60 (T = RSiO1.5). The T60 preparation can be performed using a normal hydrolytic condensation of [(3-methacryloxy)propyl]trimethoxysilane (MPMS) as an example. Theoretically, four 3sp3 hybrid orbitals (each containing an unpaired electron) of a Si atom are generated before the bond formation. Then it bonds to another four atom electrons using the four generated hybrid orbitals which produced a stable configuration. This fullerene-like silsesquioxane should exhibit much more functionality, activity and selectivity and is easier to assemble than the double bonds in a fullerene. Full article
(This article belongs to the Special Issue Conjugated Polymers 2016)
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<p>The molecular structures: (<b>a</b>) FBB, the C atom on the FBB surface connects the other three C atoms; (<b>b</b>) HBB, the Si atom connects the bridged three O atoms on the T<sub>60</sub> surface and one organic group R outside the HBB surface.</p> Full article ">Figure 2
<p>The UV-MALDI-TOF MS in the <span class="html-italic">m</span>/<span class="html-italic">z</span> = 500–11,000 Da range correspond to the MSSO oligomers.</p> Full article ">Figure 3
<p>Structures of three high-symmetry complete MSSOs: (<b>a</b>) T<sub>8</sub>; (<b>b</b>) T<sub>20</sub> and (<b>c</b>) T<sub>60</sub>.</p> Full article ">Figure 4
<p>The mass distribution of the MSSO oligomers measured by a GPC device which provides refractive index data: (<b>a</b>) reaction under 70 °C for 12 days; (<b>b</b>) reaction under 35 °C for 20 days, average molecular weights of oligomers formed in three successive groups with (<b>b1</b>) 16,260.0, (<b>b2</b>) 4538.8 and (<b>b3</b>) 1413.8, corresponding to fractions containing the T<sub>60</sub>, T<sub>20</sub> and T<sub>8</sub> cyclic compounds.</p> Full article ">
8668 KiB  
Article
Silica Treatments: A Fire Retardant Strategy for Hemp Fabric/Epoxy Composites
by Francesco Branda, Giulio Malucelli, Massimo Durante, Alessandro Piccolo, Pierluigi Mazzei, Aniello Costantini, Brigida Silvestri, Miriam Pennetta and Aurelio Bifulco
Polymers 2016, 8(8), 313; https://doi.org/10.3390/polym8080313 - 22 Aug 2016
Cited by 48 | Viewed by 9996
Abstract
In this paper, for the first time, inexpensive waterglass solutions are exploited as a new, simple and ecofriendly chemical approach for promoting the formation of a silica-based coating on hemp fabrics, able to act as a thermal shield and to protect the latter [...] Read more.
In this paper, for the first time, inexpensive waterglass solutions are exploited as a new, simple and ecofriendly chemical approach for promoting the formation of a silica-based coating on hemp fabrics, able to act as a thermal shield and to protect the latter from heat sources. Fourier Transform Infrared (FTIR) and solid-state Nuclear Magnetic Resonance (NMR) analysis confirm the formation of –C–O–Si– covalent bonds between the coating and the cellulosic substrate. The proposed waterglass treatment, which is resistant to washing, seems to be very effective for improving the fire behavior of hemp fabric/epoxy composites, also in combination with ammonium polyphosphate. In particular, the exploitation of hemp surface treatment and Ammonium Polyphosphate (APP) addition to epoxy favors a remarkable decrease of the Heat Release Rate (HRR), Total Heat Release (THR), Total Smoke Release (TSR) and Specific Extinction Area (SEA) (respectively by 83%, 35%, 45% and 44%) as compared to untreated hemp/epoxy composites, favoring the formation of a very stable char, as also assessed by Thermogravimetric Analysis (TGA). Because of the low interfacial adhesion between the fabrics and the epoxy matrix, the obtained composites show low strength and stiffness; however, the energy absorbed by the material is higher when using treated hemp. The presence of APP in the epoxy matrix does not affect the mechanical behavior of the composites. Full article
(This article belongs to the Special Issue Recent Advances in Flame Retardancy of Textile Related Products)
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<p>Fourier Transform Infrared (FTIR) spectra of (<b>a</b>) untreated (black line); (<b>b</b>) after two (red) and (<b>c</b>) five (blue) soaking/drying cycles.</p> Full article ">Figure 2
<p>Scanning Electron Microscope (SEM) images of: (<b>a</b>) untreated hemp fabric (scale bar: 10 μm); (<b>b</b>) hemp fabric after the waterglass treatment (scale bar: 3 μm).</p> Full article ">Figure 3
<p>Solid-state Nuclear Magnetic Resonance (NMR) spectrum of untreated hemp fabric.</p> Full article ">Figure 4
<p>Solid-state NMR spectra of untreated hemp fabric (blue) and hemp fabric after the waterglass treatment (red).</p> Full article ">Figure 5
<p><sup>29</sup>Si NMR spectra of hemp (H, blue) and treated hemp (HT, red) samples acquired at a spin rate 10,000 Hz.</p> Full article ">Figure 6
<p>Thermogravimetry (TG) (<b>a</b>) and dTG (<b>b</b>) curves in an inert atmosphere for hemp, before (black line) and after (red line) the waterglass treatment.</p> Full article ">Figure 7
<p>TG (<b>a</b>) and dTG (<b>b</b>) curves in an inert atmosphere for the investigated composite.</p> Full article ">Figure 8
<p>Residue of H/E-15APP after cone calorimetry tests.</p> Full article ">Figure 9
<p>Residue of HT/E-15APP after cone calorimetry tests.</p> Full article ">Figure 10
<p>Stress-strain curves for the four types of composites: H/E sample, H/E-15APP sample, HT/E sample, HT/E-15APP sample.</p> Full article ">Figure 11
<p>Images of the fracture for the tensile stress in the section (<b>a</b>) (140×) and in the plane (<b>b</b>) (100×) view.</p> Full article ">
4128 KiB  
Article
Chemo-Enzymatic Synthesis of Perfluoroalkyl-Functionalized Dendronized Polymers as Cyto-Compatible Nanocarriers for Drug Delivery Applications
by Badri Parshad, Meena Kumari, Katharina Achazi, Christoph Bӧttcher, Rainer Haag and Sunil K. Sharma
Polymers 2016, 8(8), 311; https://doi.org/10.3390/polym8080311 - 18 Aug 2016
Cited by 16 | Viewed by 6534
Abstract
Among amphiphilic polymers with diverse skeletons, fluorinated architectures have attracted significant attention due to their unique property of segregation and self-assembly into discrete supramolecular entities. Herein, we have synthesized amphiphilic copolymers by grafting hydrophobic alkyl/perfluoroalkyl chains and hydrophilic polyglycerol [G2.0] dendrons onto a [...] Read more.
Among amphiphilic polymers with diverse skeletons, fluorinated architectures have attracted significant attention due to their unique property of segregation and self-assembly into discrete supramolecular entities. Herein, we have synthesized amphiphilic copolymers by grafting hydrophobic alkyl/perfluoroalkyl chains and hydrophilic polyglycerol [G2.0] dendrons onto a co-polymer scaffold, which itself was prepared by enzymatic polymerization of poly[ethylene glycol bis(carboxymethyl) ether]diethylester and 2-azidopropan-1,3-diol. The resulting fluorinated polymers and their alkyl chain analogs were then compared in terms of their supramolecular aggregation behavior, solubilization capacity, transport potential, and release profile using curcumin and dexamethasone drugs. The study of the release profile of encapsulated curcumin incubated with/without a hydrolase enzyme Candida antarctica lipase (CAL-B) suggested that the drug is better stabilized in perfluoroalkyl chain grafted polymeric nanostructures in the absence of enzyme for up to 12 days as compared to its alkyl chain analogs. Although both the fluorinated as well as non-fluorinated systems showed up to 90% release of curcumin in 12 days when incubated with lipase, a comparatively faster release was observed in the fluorinated polymers. Cell viability of HeLa cells up to 95% in aqueous solution of fluorinated polymers (100 ?g/mL) demonstrated their excellent cyto-compatibility. Full article
(This article belongs to the Special Issue Enzymatic Polymer Synthesis)
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<p>Evaluation of CAC of polymers using pyrene as a hydrophobic probe and by measuring I<sub>3</sub>/I<sub>1</sub> ratio: (<b>A</b>) polymers <b>5a</b> and <b>5b</b>; (<b>B</b>) polymers <b>5c</b> and <b>5d</b>.</p> Full article ">Figure 2
<p>Cryo-TEM images of polymers, (<b>a</b>) <b>5a</b>; (<b>b</b>) <b>5b</b> showing individual spherical micelles in the diameter range of 5 nm; (<b>c</b>) Cryo-TEM image of individual spherical micelles of ~8 nm in diameter formed upon encapsulation of curcumin encapsulated by polymer <b>5a</b>.</p> Full article ">Figure 3
<p>(<b>A</b>) Absorbance spectra of curcumin encapsulated samples in methanol; (<b>B</b>) emission spectra of curcumin encapsulated samples in methanol.</p> Full article ">Figure 4
<p>Quantification of curcumin encapsulated by polymers: (<b>A</b>) transport capacity; (<b>B</b>) transport efficiency.</p> Full article ">Figure 5
<p>Enzyme-triggered systematic release of hydrophobic molecules from amphiphilic polymers.</p> Full article ">Figure 6
<p>Intensity of emission of curcumin encapsulated in nanocarriers having pH 7.4 (1× PBS buffer) and incubated with and without enzyme at 37 °C (<b>A</b>) <b>5a</b>; (<b>B</b>) <b>5d</b>.</p> Full article ">Figure 7
<p><sup>19</sup>F NMR spectra of dexamethasone encapsulated polymers (<b>5a</b>, <b>5b</b>, <b>5c</b>, and <b>5d</b>) and blank dexamethasone in deuterated methanol; 5-fluorouracil (2 mg/mL) used as internal reference.</p> Full article ">Scheme 1
<p>Synthesis of functionalized amphiphilic polymers: (i) [Cu(PPh<sub>3</sub>)<sub>3</sub>]Br, DIPEA, DCM/DMF.</p> Full article ">
7230 KiB  
Review
Stimuli-Directed Helical Chirality Inversion and Bio-Applications
by Ziyu Lv, Zhonghui Chen, Kenan Shao, Guangyan Qing and Taolei Sun
Polymers 2016, 8(8), 310; https://doi.org/10.3390/polym8080310 - 18 Aug 2016
Cited by 45 | Viewed by 11901
Abstract
Helical structure is a sophisticated ubiquitous motif found in nature, in artificial polymers, and in supramolecular assemblies from microscopic to macroscopic points of view. Significant progress has been made in the synthesis and structural elucidation of helical polymers, nevertheless, a new direction for [...] Read more.
Helical structure is a sophisticated ubiquitous motif found in nature, in artificial polymers, and in supramolecular assemblies from microscopic to macroscopic points of view. Significant progress has been made in the synthesis and structural elucidation of helical polymers, nevertheless, a new direction for helical polymeric materials, is how to design smart systems with controllable helical chirality, and further use them to develop chiral functional materials and promote their applications in biology, biochemistry, medicine, and nanotechnology fields. This review summarizes the recent progress in the development of high-performance systems with tunable helical chirality on receiving external stimuli and discusses advances in their applications as drug delivery vesicles, sensors, molecular switches, and liquid crystals. Challenges and opportunities in this emerging area are also presented in the conclusion. Full article
(This article belongs to the Special Issue Responsive Polymers for Drug Delivery, Imaging and Theranostic Functions)
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<p>Schematic illustration of helical chirality inversion through different external stimuli, such as solvent, light irradiation, ion, temperature and pH. Typical examples for these modulate methods are also displayed. Reproduced from [<a href="#B21-polymers-08-00310" class="html-bibr">21</a>,<a href="#B22-polymers-08-00310" class="html-bibr">22</a>,<a href="#B23-polymers-08-00310" class="html-bibr">23</a>,<a href="#B24-polymers-08-00310" class="html-bibr">24</a>,<a href="#B25-polymers-08-00310" class="html-bibr">25</a>] with copyright permission.</p> Full article ">Figure 2
<p>(<b>a</b>) Asymmetric hydrosilylation of styrenes using a PQXphos variant as ligand. Switching of enantioinduction in this reaction can be achieved by tuning the helix of the ligand via solvent stimuli; (<b>b</b>) DBA-OC10 can self-assemble into well-organized counterclockwise or clockwise nanopatterns at the (S)-2-octanol/highly oriented pyrolytic graphite (HOPG, left) and (<span class="html-italic">R</span>)-2-octanol/HOPG interface (right), respectively, observed by high resolution-scanning tunneling microscope (HR-STM). Reproduced from [<a href="#B37-polymers-08-00310" class="html-bibr">37</a>] with copyright permission.</p> Full article ">Figure 3
<p>(<b>a</b>) Chemical structure of light-driven molecular motor; (<b>b</b>) Schematic illustration of one full rotary cycle by photo and thermally stimuli; (<b>c</b>) The catalytic reaction scheme and conditions; (<b>d</b>) HPLC traces of the reaction product utilizing catalyst in state 1 (<span class="html-italic">S</span>/<span class="html-italic">R</span> = 49/51), state 2 (<span class="html-italic">S</span>/<span class="html-italic">R</span> = 75/25) and state 3 (<span class="html-italic">S</span>/<span class="html-italic">R</span> = 23/77), respectively. Reproduced from [<a href="#B40-polymers-08-00310" class="html-bibr">40</a>] with copyright permission.</p> Full article ">Figure 4
<p>(<b>a</b>) Ribbons show distinct macroscopic shapes depending on the direction they are cut, ribbon A is almost flat, ribbon C exhibits an open-ring shape, ribbon B and D displayed left-handed or right-handed shape, respectively. (<b>b</b>) The mechanical motions (i.e., winding, unwinding, and helix inversion) can be observed by the naked eye via different ribbons triggered by UV light irradiation. Reproduced from [<a href="#B50-polymers-08-00310" class="html-bibr">50</a>] with copyright permission.</p> Full article ">Figure 5
<p>Scheme illustration of selective regulation of the helix sense by control of the conformation of the pendants upon Ag<sup>+</sup> or Ba<sup>2+</sup>, respectively (upper part); AFM images and theoretical models (form the top and side views) of left-handed helix of polymer/Ag<sup>+</sup>, or right-handed helix of polymer/Ba<sup>2+</sup> (lower part). Reproduced from [<a href="#B23-polymers-08-00310" class="html-bibr">23</a>] with copyright permission.</p> Full article ">Figure 6
<p>(<b>a</b>) Molecular structures of enantiomeric bent-shaped amphiphiles 2a (left) and 2b (right); (<b>b</b>) TEM images of 2a tubules (0.01 wt % aqueous solution) prepared at 60 °C or room temperature (inset), scale bar: 100 nm; (<b>c</b>) Schematic illustration of pulsating rotation of the nanotubules accompanied by a chiral inversion, triggered by using thermal stimuli; (<b>d</b>) Schematic illustration of thermo-modulated packing variations of encapsulated C<sub>60</sub> molecules. Reproduced from [<a href="#B25-polymers-08-00310" class="html-bibr">25</a>] with copyright permission.</p> Full article ">Figure 7
<p>Schematic illustration of switchable enantioseparation (trans-stilbene oxide) by poly-1 stationary phase. Through <span class="html-italic">R</span>/<span class="html-italic">S</span>-phenylethanol stimulus, the original racemic helicity can turn into P-helix or M-helix, generating a great impact on the elution order of trans-stilbene oxide enantiomers. Reproduced from [<a href="#B75-polymers-08-00310" class="html-bibr">75</a>] with copyright permission.</p> Full article ">
2073 KiB  
Article
Molecularly Imprinted Polymers Based Electrochemical Sensor for 2,4-Dichlorophenol Determination
by Benzhi Liu, Hui Cang and Jianxiang Jin
Polymers 2016, 8(8), 309; https://doi.org/10.3390/polym8080309 - 18 Aug 2016
Cited by 20 | Viewed by 5661
Abstract
A molecularly imprinted polymers based electrochemical sensor was fabricated by electropolymerizing pyrrole on a Fe3O4 nanoparticle modified glassy carbon electrode. The sensor showed highly catalytic ability for the oxidation of 2,4-dichlorophenol (2,4-DCP). Square wave voltammetry was used for the determination [...] Read more.
A molecularly imprinted polymers based electrochemical sensor was fabricated by electropolymerizing pyrrole on a Fe3O4 nanoparticle modified glassy carbon electrode. The sensor showed highly catalytic ability for the oxidation of 2,4-dichlorophenol (2,4-DCP). Square wave voltammetry was used for the determination of 2,4-DCP. The oxidation peak currents were proportional to the concentrations of 2,4-DCP in the range of 0.04 to 2.0 µM, with a detection limit of 0.01 µM. The proposed sensor was successfully applied for the determination of 2,4-DCP in water samples giving satisfactory recoveries. Full article
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<p>The procedure for the preparation of molecularly imprinted polymers modified glassy carbon electrode (MIPs/Fe<sub>3</sub>O<sub>4</sub>/GCE).</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) images of (<b>A</b>) Fe<sub>3</sub>O<sub>4</sub> nanoparticles; (<b>B</b>) MIPs/Fe<sub>3</sub>O<sub>4</sub>; and (<b>C</b>) high resolution of MIPs/Fe<sub>3</sub>O<sub>4</sub>.</p> Full article ">Figure 2 Cont.
<p>Scanning electron microscopy (SEM) images of (<b>A</b>) Fe<sub>3</sub>O<sub>4</sub> nanoparticles; (<b>B</b>) MIPs/Fe<sub>3</sub>O<sub>4</sub>; and (<b>C</b>) high resolution of MIPs/Fe<sub>3</sub>O<sub>4</sub>.</p> Full article ">Figure 3
<p>Cyclic voltammograms (CVs) of modified electrodes in 0.1 mol·L<sup>−1</sup> phosphate buffer solution (PBS) containing 50 μM of 2,4-DCP. Scan rate: 0.1 Vs<sup>−1</sup>.</p> Full article ">Figure 4
<p>Influences of different preparation conditions on the response of the sensor to 20 μM of 2,4-DCP: (<b>A</b>) amount of Fe<sub>3</sub>O<sub>4</sub> nanoparticles; (<b>B</b>) the ratio of template/monomer; (<b>C</b>) electropolymerization scan cycles; (<b>D</b>) scan rate; (<b>E</b>) incubation time.</p> Full article ">Figure 5
<p>Square wave voltammetry (SWVs) of MIPs/Fe<sub>3</sub>O<sub>4</sub>/GCE in solution containing different concentrations of 2,4-DCP, from <b>a</b>–<b>g</b>: 0, 0.04, 0.16, 0.32, 0.56, 1.2, 2.0 µM. Inset: plot of peak current versus 2,4-DCP concentration.</p> Full article ">Figure 6
<p>The peak current changes of 0.3 µM 2,4-DCP at MIPs/Fe<sub>3</sub>O<sub>4</sub>/GCE with addition of 5-fold concentration of interference species: (<b>a</b>) 2-chlorophenol; (<b>b</b>) hydroxyphenol; (<b>c</b>) pentachlorophenol; (<b>d</b>) 2,4,6-trichlorophenol; (<b>e</b>) hydroquinol.</p> Full article ">
5772 KiB  
Article
A Retrofit Theory to Prevent Fatigue Crack Initiation in Aging Riveted Bridges Using Carbon Fiber-Reinforced Polymer Materials
by Elyas Ghafoori and Masoud Motavalli
Polymers 2016, 8(8), 308; https://doi.org/10.3390/polym8080308 - 18 Aug 2016
Cited by 30 | Viewed by 8789
Abstract
Most research on fatigue strengthening of steel has focused on carbon fiber-reinforced polymer (CFRP) strengthening of steel members with existing cracks. However, in many practical cases, aging steel members do not yet have existing cracks but rather are nearing the end of their [...] Read more.
Most research on fatigue strengthening of steel has focused on carbon fiber-reinforced polymer (CFRP) strengthening of steel members with existing cracks. However, in many practical cases, aging steel members do not yet have existing cracks but rather are nearing the end of their designed fatigue life. Therefore, there is a need to develop a “proactive” retrofit solution that can prevent fatigue crack initiation in aging bridge members. Such a proactive retrofit approach can be applied to bridge members that have been identified to be deficient, based on structural standards, to enhance their safety margins by extending the design service life. This paper explains a proactive retrofit design approach based on constant life diagram (CLD) methodology. The CLD approach is a method that can take into account the combined effect of alternating and mean stress magnitudes to predict the high-cycle fatigue life of a material. To validate the retrofit model, a series of new fatigue tests on steel I-beams retrofitted by the non-prestressed un-bonded CFRP plates have been conducted. Furthermore, this paper attempts to provide a better understanding of the behavior of un-bonded retrofit (UR) and bonded retrofit (BR) systems. Retrofitting the steel beams using the UR system took less than half of the time that was needed for strengthening with the BR system. The results show that the non-prestressed un-bonded ultra-high modulus (UHM) CFRP plates can be effective in preventing fatigue crack initiation in steel members. Full article
(This article belongs to the Special Issue Selected Papers from “SMAR 2015”)
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Full article ">Figure 1
<p>Stress cycles with different stress ratios of <span class="html-italic">R</span> = 0, −1 and −∞.</p> Full article ">Figure 2
<p>Stresses at (<b>a</b>) gross cross-section; (<b>b</b>) at notch in elastic and (<b>c</b>) plastic range.</p> Full article ">Figure 3
<p>Illustration of different fatigue failure zones in the constant life diagram (CLD) approach.</p> Full article ">Figure 4
<p>The stress at the bottom flange of a beam subjected to external cyclic loading, P, when the beam is (<b>a</b>) not strengthened; (<b>b</b>) strengthened with the pre-stressed NM CFRP plate or (<b>c</b>) strengthened with the ultra-high modulus (UHM) plates; (<b>d</b>) A CLD that indicates the stresses prior to and after strengthening.</p> Full article ">Figure 5
<p>Four-point bending test set-up (dimensions in mm).</p> Full article ">Figure 6
<p>Strengthening set-up. (<b>a</b>) A manual hydraulic jack is used to stretch the CFRP plate; (<b>b</b>) mechanical clamps are used to fix the plate to the beam in the un-bonded systems; (<b>c</b>) in bonded systems, adhesive are applied on top of the CFRP plate and (<b>d</b>) the beam is placed on top of the plate for at least 24 h for curing.</p> Full article ">Figure 7
<p>Comparison between the times needed for strengthening steel beams using the bonded retrofit (BR) and un-bonded retrofit (UR) systems.</p> Full article ">Figure 8
<p>(<b>a</b>) Specimens strengthened with the BR system; (<b>b</b>) Measurement layout for the BR system; (<b>c</b>) specimens strengthened with the UR system; (<b>d</b>) measurement layout for the UR system [<a href="#B27-polymers-08-00308" class="html-bibr">27</a>]; (<b>e</b>) details of the two drilled holes in the bottom flange of the fatigue specimens, the CFRP laminate and strain gauges (dimensions in mm).</p> Full article ">Figure 8 Cont.
<p>(<b>a</b>) Specimens strengthened with the BR system; (<b>b</b>) Measurement layout for the BR system; (<b>c</b>) specimens strengthened with the UR system; (<b>d</b>) measurement layout for the UR system [<a href="#B27-polymers-08-00308" class="html-bibr">27</a>]; (<b>e</b>) details of the two drilled holes in the bottom flange of the fatigue specimens, the CFRP laminate and strain gauges (dimensions in mm).</p> Full article ">Figure 9
<p>Measured Young’s modulus of the CFRP plates.</p> Full article ">Figure 10
<p>The load-deflection behavior of reference specimen B0 and specimen B2 (retrofitted with the un-bonded NM CFRP plate).</p> Full article ">Figure 11
<p>The measured and calculated strains along the CFRP plates for the specimens strengthened with bonded and un-bonded HM CFRP plates (i.e., B3 and B4, respectively).</p> Full article ">Figure 12
<p>The measured and calculated strains along the bonded and un-bonded CFRP plates for the specimens strengthened with the NM, HM and UHM CFRP plates when the specimen is subjected to an actuator load level of <span class="html-italic">P</span> = 40 kN.</p> Full article ">Figure 13
<p>(<b>a</b>) Holes drilled in the beam bottom flange; (<b>b</b>) crack emanating from stress concentration location; (<b>c</b>) different stages of fracture failures: crack initiation, crack propagation and a sudden fracture failure; (<b>d</b>) fatigue crack initiated from the hole of the retrofitted specimen and propagated into the steel web.</p> Full article ">Figure 14
<p>The CLD illustration of the experimental and modeling results. As the Young’s modulus of the CFRP plate increases, the stresses approach the safe zone along the original stress-ratio line.</p> Full article ">
4497 KiB  
Article
Influence of Carbon Nanotube Coatings on Carbon Fiber by Ultrasonically Assisted Electrophoretic Deposition on Its Composite Interfacial Property
by Jianjun Jiang, Chumeng Xu, Yang Su, Qiang Guo, Fa Liu, Chao Deng, Xuming Yao and Linchao Zhou
Polymers 2016, 8(8), 302; https://doi.org/10.3390/polym8080302 - 17 Aug 2016
Cited by 30 | Viewed by 7153
Abstract
Carbon nanotube (CNT) coatings were utilized to enhance the interfacial properties of carbon fiber (CF)/epoxy(EP) composites by ultrasonically assisted electrophoretic deposition (EPD). A characterization of the CF surface properties was done before and after coating (surface chemistry, surface morphologies, and surface energy). The [...] Read more.
Carbon nanotube (CNT) coatings were utilized to enhance the interfacial properties of carbon fiber (CF)/epoxy(EP) composites by ultrasonically assisted electrophoretic deposition (EPD). A characterization of the CF surface properties was done before and after coating (surface chemistry, surface morphologies, and surface energy). The result shows that oxygenated groups concentrations of the CF surfaces experienced significant increases from 12.11% to 24.78%. Moreover, the uniform and homogeneous CNT films were tightly attached on the surface of CF, and the surface wettability of CF is significant improved by enhanced surface free energy when introduced ultrasonic during the EPD process. In addition, the interlaminar shear strength (ILSS) and water absorption of CF/EP composite were measured. Scanning electron microscopy (SEM) revealed that the fracture mechanisms of the new interface layer formed by depositing CNTs on the CF surface contributed to the enhancement of the mechanical performance of the epoxy. This means that the efficient method to improve interfacial performance of composites has shown great commercial application potential. Full article
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<p>Schematic for ultrasonically assisted electrophoretic deposition (EPD) process of carbon nanotubes (CNTs) onto carbon fiber.</p> Full article ">Figure 2
<p>(<b>a</b>) TEM image of carbon nanotubes (CNTs); (<b>b</b>) UV–vis spectra of the untreated and base-treated CNTs.</p> Full article ">Figure 3
<p>Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of carbon fiber (<b>a</b>,<b>d</b>) desized; (<b>b</b>,<b>e</b>) CNTs deposited without ultrasonic; (<b>c</b>,<b>f</b>) CNTs deposited with ultrasonic.</p> Full article ">Figure 4
<p>(<b>a</b>) The X-ray photoelectron spectroscopy (XPS) wide-scan spectra; (<b>b</b>) C1s spectra of desized carbon fiber (CF); (<b>c</b>) C1s spectra of desized CF without ultrasonic; (<b>d</b>) C1s spectra of desized CF with ultrasonic.</p> Full article ">Figure 5
<p>Interlaminar shear strength (ILSS) of the composites reinforced by the desized CF, CNTs deposited CF without ultrasonication, CNTs deposited CF with ultrasonication.</p> Full article ">Figure 6
<p>Water absorption of the composites reinforced by the desized CF, CNTs deposited CF without ultrasonication, CNTs deposited CF with ultrasonication.</p> Full article ">Figure 7
<p>Fractured SEM images of CF/epoxy (EP) composite (<b>a</b>) desized CF; (<b>b</b>) CNT deposited CF without ultrasonication; (<b>c</b>) CNTs deposited CF with ultrasonication.</p> Full article ">Figure 8
<p>Schema for the differences between pristine and sonicated composites.</p> Full article ">
149 KiB  
Editorial
Interdisciplinary Approaches towards Materials with Enhanced Properties for Electrical Engineering
by Frank Wiesbrock
Polymers 2016, 8(8), 307; https://doi.org/10.3390/polym8080307 - 16 Aug 2016
Viewed by 3431
Abstract
The internationally growing demand for electrical energy is one of the most prominent triggers stimulating research these days.[...] Full article
(This article belongs to the Special Issue Nano- and Microcomposites for Electrical Engineering Applications)
10704 KiB  
Article
Protein-Repellence PES Membranes Using Bio-grafting of Ortho-aminophenol
by Norhan Nady, Ahmed H. El-Shazly, Hesham M. A. Soliman and Sherif H. Kandil
Polymers 2016, 8(8), 306; https://doi.org/10.3390/polym8080306 - 15 Aug 2016
Cited by 3 | Viewed by 6591
Abstract
Surface modification becomes an effective tool for improvement of both flux and selectivity of membrane by reducing the adsorption of the components of the fluid used onto its surface. A successful green modification of poly(ethersulfone) (PES) membranes using ortho-aminophenol (2-AP) modifier and laccase [...] Read more.
Surface modification becomes an effective tool for improvement of both flux and selectivity of membrane by reducing the adsorption of the components of the fluid used onto its surface. A successful green modification of poly(ethersulfone) (PES) membranes using ortho-aminophenol (2-AP) modifier and laccase enzyme biocatalyst under very flexible conditions is presented in this paper. The modified PES membranes were evaluated using many techniques including total color change, pure water flux, and protein repellence that were related to the gravimetric grafting yield. In addition, static water contact angle on laminated PES layers were determined. Blank and modified commercial membranes (surface and cross-section) and laminated PES layers (surface) were imaged by scanning electron microscope (SEM) and scanning probe microscope (SPM) to illustrate the formed modifying poly(2-aminophenol) layer(s). This green modification resulted in an improvement of both membrane flux and protein repellence, up to 15.4% and 81.27%, respectively, relative to the blank membrane. Full article
(This article belongs to the Special Issue Enzymatic Polymer Synthesis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Molecular structure of 2-aminophenol, 4-aminophenol, phenoxazine, and 2,2′-dihydroxyazobenzene.</p> Full article ">Figure 2
<p>Tentative mechanism for the reaction of laccase-generated radicals with poly(ethersulfone) (PES), and subsequent formation of grafted brushes [<a href="#B50-polymers-08-00306" class="html-bibr">50</a>].</p> Full article ">Figure 3
<p>Change of the membrane color (∆E*) with grafting yield; common reaction condition is pH 5.5 (0.1 M sodium acetate buffer), and 0.5 U·mL<sup>−1</sup> enzyme (laccase). Reaction at 25 °C using 5 mM 2-AP (blue diamond) and 15 mM 2-AP (red diamond), and reaction at 40 °C using 5 mM 2-AP (green circle) and 15 mM 2-AP (purple circle). Resection times 30, 60, and 120 min were tested and the grafting yield was increased with increasing the reaction time. The solid black line is a guide for general trend.</p> Full article ">Figure 4
<p>The effect of the grafting yield on the pure water flux of the membrane. Common reaction condition is pH 5.5 (0.1 M sodium acetate buffer), and 0.5 U·mL<sup>−1</sup> enzyme (laccase). Reaction at 25 °C using 5 mM 2-AP (blue diamond) and 15 mM 2-AP (red diamond), and reaction at 40 °C using 5 mM 2-AP (green circle) and 15 mM 2-AP (purple circle). Resection times 30, 60, and 120 min were tested and the grafting yield was increased with increasing the reaction time. The solid and dashed lines are guides for general trend for the studied conditions.</p> Full article ">Figure 5
<p>Change of the static water contact angle with the reaction (modification) time. Common reaction condition is pH 5.5 (0.1 M sodium acetate buffer), and 0.5 U·mL<sup>−1</sup> enzyme (laccase). Two modifier concentrations, 5 mM (blue) and 15 mM (red) (2-aminophenol), were used at 25 °C reaction temperature and 15, 30, 60, and 120 min reaction times. The solid lines are guides for general trend for the studied conditions.</p> Full article ">Figure 6
<p>The effect of the grafting yield on the irreversible protein adsorption. Common reaction condition is pH 5.5 (0.1 M sodium acetate buffer), and 0.5 U·mL<sup>−1</sup> enzyme (laccase). Reaction at 25 °C using 5 mM 2-AP (blue diamond) and 15 mM 2-AP (red diamond), and reaction at 40 °C using 5 mM 2-AP (green circle) and 15 mM 2-AP (purple circle). Resection times 30, 60, and 120 min were tested and the grafting yield was increased with increasing the reaction time. Adsorption test was done using 1 g·L<sup>−1</sup> BSA, 0.1 M sodium acetate buffer (pH 7) and 25 °C.</p> Full article ">Figure 7
<p>Flux reduction percent due to the irreversible protein adsorption at different grafting yield. Common reaction condition is pH 5.5 (0.1 M sodium acetate buffer), and 0.5 U·mL<sup>−1</sup> enzyme (laccase). Reaction at 25 °C using 5 mM 2-AP (blue diamond) and 15 mM 2-AP (red diamond), and reaction at 40 °C using 5 mM 2-AP (green circle) and 15 mM 2-AP (purple circle). Resection times 30, 60, and 120 min were tested and the grafting yield was increased with increasing the reaction time. The solid and dashed lines are guides for general trend for the studied conditions.</p> Full article ">Figure 8
<p>The scanning electron microscope (SEM) images for the blank poly(ethersulfone) (PES) membrane, and the modified PES membranes: (<b>A</b>,<b>B</b>) modified PES membranes using 5 and 15 mM modifier (2-AP), respectively at 25 °C; and (<b>C</b>,<b>D</b>) modified PES membranes using 5 and 15 mM 2-AP, respectively at 40 °C. Common reaction condition is pH 5.5 (0.1 M sodium acetate buffer), 0.5 U·mL<sup>−1</sup> enzyme (laccase), and 120 min modification time. Magnification is 15,000×; and scale bar is 1 µm.</p> Full article ">Figure 9
<p>The scanning electron microscope (SEM) images for the cross-section of the blank poly(ethersulfone) (PES) membrane, (<b>A</b>) 5000× and (<b>D</b>) 15,000×; the modified PES membrane using 5 mM 2-AP and at 25 °C reaction temperature, (<b>B</b>) 5000× and (<b>E</b>) 15,000×; and modified PES membrane using 15 mM 2-AP and at 40 °C, (<b>C</b>) 5000× and (<b>F</b>) 15,000×. Common reaction condition is pH 5.5 (0.1 M sodium acetate buffer), 0.5 U·mL<sup>−1</sup> enzyme (laccase), and 60 min reaction (modification) time.</p> Full article ">Figure 10
<p>The scanning electron microscope (SEM) of the laminated poly(ethersulfone) (PES) layer on silicon dioxide slides using 15,000× and 30,000× magnification: (<b>A</b>,<b>B</b>) the blank laminated PES layer at the two magnifications; and (<b>C</b>,<b>D</b>) the modified laminated PES layer at the two magnifications using modification condition: 15 mM 2-AP, pH 5.5 (0.1 M sodium acetate buffer), and 0.5 U·mL<sup>−1</sup> enzyme (laccase) modified for 60 min at 25 °C.</p> Full article ">Figure 11
<p>The scanning probe microscope (SPM) of the laminated PES layer on silicon dioxide slides: the blank laminated PES layer (<b>A</b>); and modified laminated PES layer (<b>B</b>). Modification condition: 15 mM 2-AP, pH 5.5 (0.1 M sodium acetate buffer), and 0.5 U·mL<sup>−1</sup> enzyme (laccase) modified for 120 min at 25 °C.</p> Full article ">Figure 12
<p>Effect of the grafting yield on the tensile strength of the blank poly(ethersulfone) (PES) membrane. Common reaction condition is pH 5.5 (0.1 M sodium acetate buffer), and 0.5 U·mL<sup>−1</sup> enzyme (laccase). Reaction at 25 °C using 5 mM 2-AP (blue diamond) and 15 mM 2-AP (red diamond), and reaction at 40 °C using 5 mM 2-AP (green circle) and 15 mM 2-AP (purple circle). Resection times 30, 60, and 120 min were tested and the grafting yield was increased with increasing the reaction time.</p> Full article ">Figure 13
<p>Schematic representation of four possible chemical structures of the poly(ethersulfone) (PES) surface after modification with 2-aminophenol, containing O-linked and N-linked structures.</p> Full article ">
2884 KiB  
Article
Study of Polymer Matrix Degradation Behavior in CFRP Short Pulsed Laser Processing
by Hebing Xu and Jun Hu
Polymers 2016, 8(8), 299; https://doi.org/10.3390/polym8080299 - 15 Aug 2016
Cited by 26 | Viewed by 5885
Abstract
Short pulsed laser is preferred to avoid the thermal damage in processing the heat sensitive material, such as carbon fiber reinforced plastic (CFRP). In this paper, a numerical model capturing both the material ablation and polymer matrix pyrolysis processes in pulsed laser processing [...] Read more.
Short pulsed laser is preferred to avoid the thermal damage in processing the heat sensitive material, such as carbon fiber reinforced plastic (CFRP). In this paper, a numerical model capturing both the material ablation and polymer matrix pyrolysis processes in pulsed laser processing is established. The effect of laser pulse length from ns order to ?s order is studied. It was found that with shorter pulse length, ablation depth is increased and heat affected zone is remarkably reduced. Moreover the pyrolysis gas transport analysis shows that shorter pulse length results in a larger internal pressure. At pulse length in ns order, maximum pressure as high as hundreds of times atmospheric pressure in CFRP could be produced and leads to mechanical erosion of material. The predicted ablation depth of a single short laser pulse conforms well to the experiment result of the CFRP laser milling experiment. Full article
(This article belongs to the Special Issue Polymeric Fibers)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic of short pulsed laser milling of carbon fiber reinforced plastic (CFRP).</p> Full article ">Figure 2
<p>(<b>a</b>) Finite-rate pyrolysis model; (<b>b</b>) Instantaneous pyrolysis model.</p> Full article ">Figure 3
<p>Polymer volume fraction at different temperatures in a certain reaction time (10 ns, 20 μs, 2000 μs).</p> Full article ">Figure 4
<p>Effect of space step <span class="html-italic">δx</span> on the ablation boundary at time step <span class="html-italic">δt</span> = 0.001 ns.</p> Full article ">Figure 5
<p>(<b>a</b>) Temperature curve at <span class="html-italic">x</span> = 100 μm; (<b>b</b>) Temperature field at 10 ns.</p> Full article ">Figure 6
<p>The curve of pyrolysis boundary <math display="inline"> <semantics> <mrow> <msub> <mi>x</mi> <mi>b</mi> </msub> </mrow> </semantics> </math> at the cooling stage.</p> Full article ">Figure 7
<p>At the pyrolysis boundary <math display="inline"> <semantics> <mrow> <msub> <mi>x</mi> <mi>b</mi> </msub> </mrow> </semantics> </math> (<b>a</b>) Temperature curve; (<b>b</b>) Pressure curve.</p> Full article ">Figure 8
<p>(<b>a</b>) Laser milling CFRP sample; (<b>b</b>) Predicted ablation depth vs. experimental data at different laser powers.</p> Full article ">Figure 9
<p>Temperature curves at the end of different pulse lengths.</p> Full article ">Figure 10
<p>Moving boundaries at pulse lengths 5, 10, 15, 20 μs (<b>a</b>) Ablation boundary <math display="inline"> <semantics> <mrow> <msub> <mi>x</mi> <mi>a</mi> </msub> </mrow> </semantics> </math>; (<b>b</b>) Pyrolysis boundary <math display="inline"> <semantics> <mrow> <msub> <mi>x</mi> <mi>b</mi> </msub> </mrow> </semantics> </math>.</p> Full article ">Figure 11
<p>(<b>a</b>) Curves of HAZ; (<b>b</b>) Ablation depth and HAZ.</p> Full article ">Figure 12
<p>Pressure fields of different pulse lengths at <math display="inline"> <semantics> <mrow> <msub> <mi>x</mi> <mi>b</mi> </msub> </mrow> </semantics> </math> (<b>a</b>) 5 μs; (<b>b</b>) 10 μs; (<b>c</b>) 15 μs; (<b>d</b>) 20 μs.</p> Full article ">Figure 12 Cont.
<p>Pressure fields of different pulse lengths at <math display="inline"> <semantics> <mrow> <msub> <mi>x</mi> <mi>b</mi> </msub> </mrow> </semantics> </math> (<b>a</b>) 5 μs; (<b>b</b>) 10 μs; (<b>c</b>) 15 μs; (<b>d</b>) 20 μs.</p> Full article ">
1044 KiB  
Article
Conformational Properties of Active Semiflexible Polymers
by Thomas Eisenstecken, Gerhard Gompper and Roland G. Winkler
Polymers 2016, 8(8), 304; https://doi.org/10.3390/polym8080304 - 12 Aug 2016
Cited by 106 | Viewed by 10097
Abstract
The conformational properties of flexible and semiflexible polymers exposed to active noise are studied theoretically. The noise may originate from the interaction of the polymer with surrounding active (Brownian) particles or from the inherent motion of the polymer itself, which may be composed [...] Read more.
The conformational properties of flexible and semiflexible polymers exposed to active noise are studied theoretically. The noise may originate from the interaction of the polymer with surrounding active (Brownian) particles or from the inherent motion of the polymer itself, which may be composed of active Brownian particles. In the latter case, the respective monomers are independently propelled in directions changing diffusively. For the description of the polymer, we adopt the continuous Gaussian semiflexible polymer model. Specifically, the finite polymer extensibility is taken into account, which turns out to be essential for the polymer conformations. Our analytical calculations predict a strong dependence of the relaxation times on the activity. In particular, semiflexible polymers exhibit a crossover from a bending elasticity-dominated dynamics to the flexible polymer dynamics with increasing activity. This leads to a significant activity-induced polymer shrinkage over a large range of self-propulsion velocities. For large activities, the polymers swell and their extension becomes comparable to the contour length. The scaling properties of the mean square end-to-end distance with respect to the polymer length and monomer activity are discussed. Full article
(This article belongs to the Special Issue Semiflexible Polymers)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Model of the continuous semiflexible active polymer.</p> Full article ">Figure 2
<p>Normalized stretching coefficient (Lagrangian multiplier) <math display="inline"> <semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>2</mn> <mi>λ</mi> <mo>/</mo> <mn>3</mn> <mi>p</mi> </mrow> </semantics> </math> as a function of the Péclet number for the polymer bending stiffnesses <math display="inline"> <semantics> <mrow> <mi>p</mi> <mi>L</mi> <mo>=</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> </mrow> </semantics> </math>, <math display="inline"> <semantics> <msup> <mn>10</mn> <mn>2</mn> </msup> </semantics> </math>, 10, 1, <math display="inline"> <semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </semantics> </math> and <math display="inline"> <semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </semantics> </math> (bottom to top). For the other parameters, we set <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mi>L</mi> <mo>/</mo> <mi>l</mi> <mo>=</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mo>=</mo> <mn>1</mn> <mo>/</mo> <mn>3</mn> </mrow> </semantics> </math>. The dashed line for <math display="inline"> <semantics> <mrow> <mi>p</mi> <mi>L</mi> <mo>=</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> </mrow> </semantics> </math> represents the solution of the asymptotic Equation (<a href="#FD31-polymers-08-00304" class="html-disp-formula">31</a>). The straight lines indicate the power-law dependencies <math display="inline"> <semantics> <mrow> <mi>μ</mi> <mo>∼</mo> <mi>P</mi> <msup> <mi>e</mi> <mn>2</mn> </msup> </mrow> </semantics> </math> for <math display="inline"> <semantics> <mrow> <mi>p</mi> <mi>L</mi> <mo>&lt;</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>P</mi> <mi>e</mi> <mo>&lt;</mo> <mn>1</mn> </mrow> </semantics> </math>, and <math display="inline"> <semantics> <mrow> <mi>μ</mi> <mo>∼</mo> <mi>P</mi> <msup> <mi>e</mi> <mrow> <mn>4</mn> <mo>/</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics> </math> (cf. Equation (<a href="#FD32-polymers-08-00304" class="html-disp-formula">32</a>)), respectively.</p> Full article ">Figure 3
<p>Normalized stretching coefficient <math display="inline"> <semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>2</mn> <mi>λ</mi> <mo>/</mo> <mn>3</mn> <mi>p</mi> </mrow> </semantics> </math> as function of the Péclet number for <math display="inline"> <semantics> <mrow> <mi>p</mi> <mi>L</mi> <mo>=</mo> <msup> <mn>10</mn> <mn>1</mn> </msup> </mrow> </semantics> </math>, <math display="inline"> <semantics> <msup> <mn>10</mn> <mn>2</mn> </msup> </semantics> </math> and <math display="inline"> <semantics> <msup> <mn>10</mn> <mn>3</mn> </msup> </semantics> </math> (bottom to top). In all cases, we set <math display="inline"> <semantics> <mrow> <mi>l</mi> <mo>=</mo> <mn>1</mn> <mo>/</mo> <mi>p</mi> </mrow> </semantics> </math>, which corresponds to <math display="inline"> <semantics> <mrow> <mi>L</mi> <mo>/</mo> <mi>l</mi> <mo>=</mo> <mi>p</mi> <mi>L</mi> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mo>=</mo> <mn>1</mn> <mo>/</mo> <mn>3</mn> </mrow> </semantics> </math>. The dashed lines represent the solution of the asymptotic Equation (<a href="#FD31-polymers-08-00304" class="html-disp-formula">31</a>). The straight lines indicate the power-law dependencies <math display="inline"> <semantics> <mrow> <mi>μ</mi> <mo>∼</mo> <mi>P</mi> <msup> <mi>e</mi> <mrow> <mn>4</mn> <mo>/</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics> </math> for <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>μ</mi> <mo>∼</mo> <mi>P</mi> <mi>e</mi> </mrow> </semantics> </math> for <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>10</mn> </mrow> </semantics> </math> (cf. Equations (<a href="#FD32-polymers-08-00304" class="html-disp-formula">32</a>) and (<a href="#FD33-polymers-08-00304" class="html-disp-formula">33</a>), respectively).</p> Full article ">Figure 4
<p>Longest polymer relaxation times as a function of the Péclet number for the bending stiffnesses (<span class="html-italic">L</span> is fixed) <math display="inline"> <semantics> <mrow> <mi>p</mi> <mi>L</mi> <mo>=</mo> <mi>L</mi> <mo>/</mo> <mn>2</mn> <msub> <mi>l</mi> <mi>p</mi> </msub> <mo>=</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> </mrow> </semantics> </math>, <math display="inline"> <semantics> <msup> <mn>10</mn> <mn>2</mn> </msup> </semantics> </math>, 10, 1, <math display="inline"> <semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </semantics> </math> and <math display="inline"> <semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </semantics> </math> (bottom to top). The other parameters are the same as in <a href="#polymers-08-00304-f002" class="html-fig">Figure 2</a>.</p> Full article ">Figure 5
<p>Mode-number dependence of the relaxation times of active polymers with <math display="inline"> <semantics> <mrow> <mi>p</mi> <mi>L</mi> <mo>=</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics> </math> for the Péclet numbers <math display="inline"> <semantics> <mrow> <mi>P</mi> <mi>e</mi> <mo>=</mo> <msup> <mn>10</mn> <mn>1</mn> </msup> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mn>3</mn> <mo>×</mo> <msup> <mn>10</mn> <mn>1</mn> </msup> </mrow> </semantics> </math>, <math display="inline"> <semantics> <msup> <mn>10</mn> <mn>2</mn> </msup> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mn>5</mn> <mo>×</mo> <msup> <mn>10</mn> <mn>2</mn> </msup> </mrow> </semantics> </math> (bottom to top). The black squares (top) show the mode-number dependence of a flexible polymer with <math display="inline"> <semantics> <mrow> <mi>p</mi> <mi>L</mi> <mo>=</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> </mrow> </semantics> </math>. The other parameters are <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mo>=</mo> <mn>1</mn> <mo>/</mo> <mn>3</mn> </mrow> </semantics> </math>. The solid lines indicate the relations for flexible (<math display="inline"> <semantics> <mrow> <mo>∼</mo> <msup> <mi>n</mi> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics> </math>) and semiflexible (<math display="inline"> <semantics> <mrow> <mo>∼</mo> <msup> <mrow> <mo>(</mo> <mn>2</mn> <mi>n</mi> <mo>−</mo> <mn>1</mn> <mo>)</mo> </mrow> <mrow> <mo>−</mo> <mn>4</mn> </mrow> </msup> </mrow> </semantics> </math>) polymers, respectively. <math display="inline"> <semantics> <msub> <mi>τ</mi> <mn>1</mn> </msub> </semantics> </math> is the longest relaxation time.</p> Full article ">Figure 6
<p>Mean square end-to-end distances as a function of the Péclet number for the polymer bending stiffnesses <math display="inline"> <semantics> <mrow> <mi>p</mi> <mi>L</mi> <mo>=</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> </mrow> </semantics> </math>, <math display="inline"> <semantics> <msup> <mn>10</mn> <mn>2</mn> </msup> </semantics> </math>, 10, 1, <math display="inline"> <semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </semantics> </math> and <math display="inline"> <semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </semantics> </math> (bottom to top at <math display="inline"> <semantics> <mrow> <mi>P</mi> <mi>e</mi> <mo>=</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </semantics> </math>). The other parameters are the same as in <a href="#polymers-08-00304-f002" class="html-fig">Figure 2</a>. The dashed line represents the analytical solution of Equation (<a href="#FD40-polymers-08-00304" class="html-disp-formula">40</a>) with the Lagrangian multiplier of Equation (<a href="#FD31-polymers-08-00304" class="html-disp-formula">31</a>).</p> Full article ">Figure 7
<p>(<b>a</b>) Mean square end-to-end distances and (<b>b</b>) local slopes (Equation (<a href="#FD39-polymers-08-00304" class="html-disp-formula">39</a>)) as function of the polymer length (<math display="inline"> <semantics> <mrow> <mi>p</mi> <mi>L</mi> </mrow> </semantics> </math>) for the Péclet numbers <math display="inline"> <semantics> <mrow> <mi>P</mi> <mi>e</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math>, 3, 10, 30, <math display="inline"> <semantics> <msup> <mn>10</mn> <mn>2</mn> </msup> </semantics> </math> and <math display="inline"> <semantics> <msup> <mn>10</mn> <mn>3</mn> </msup> </semantics> </math> (bottom to top at <math display="inline"> <semantics> <mrow> <mi>p</mi> <mi>L</mi> <mo>=</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> </mrow> </semantics> </math>). The other parameters are the same as in <a href="#polymers-08-00304-f002" class="html-fig">Figure 2</a>. The dashed lines in (<b>a</b>) represent the analytical solution of Equation (<a href="#FD40-polymers-08-00304" class="html-disp-formula">40</a>) with the Lagrangian multiplier of Equation (<a href="#FD31-polymers-08-00304" class="html-disp-formula">31</a>).</p> Full article ">
3328 KiB  
Communication
Stabilization of Inverse Miniemulsions by Silyl-Protected Homopolymers
by Sarah Wald, Frederik R. Wurm, Katharina Landfester and Daniel Crespy
Polymers 2016, 8(8), 303; https://doi.org/10.3390/polym8080303 - 12 Aug 2016
Cited by 3 | Viewed by 6703
Abstract
Inverse (water-in-oil) miniemulsions are an important method to encapsulate hydrophilic payloads such as oligonucleotides or peptides. However, the stabilization of inverse miniemulsions usually requires block copolymers that are difficult to synthesize and/or cannot be easily removed after transfer from a hydrophobic continuous phase [...] Read more.
Inverse (water-in-oil) miniemulsions are an important method to encapsulate hydrophilic payloads such as oligonucleotides or peptides. However, the stabilization of inverse miniemulsions usually requires block copolymers that are difficult to synthesize and/or cannot be easily removed after transfer from a hydrophobic continuous phase to an aqueous continuous phase. We describe here a new strategy for the synthesis of a surfactant for inverse miniemulsions by radical addition–fragmentation chain transfer (RAFT) polymerization, which consists in a homopolymer with triisopropylsilyl protecting groups. The protecting groups ensure the efficient stabilization of the inverse (water-in-oil, w/o) miniemulsions. Nanocapsules can be formed and the protecting group can be subsequently cleaved for the re-dispersion of nanocapsules in an aqueous medium with a minimal amount of additional surfactant. Full article
(This article belongs to the Collection Silicon-Containing Polymeric Materials)
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<p>Synthesis of polymerized triisopropylsilyl acrylate (PTIPSA) by reversible addition–fragmentation chain transfer (RAFT) polymerization.</p> Full article ">Figure 2
<p>Procedure of an inverse miniemulsion with 1,4-diaminobutane (DAB) and toluene-2,4-diisocyanate (TDI) as monomers to generate polyurea (PU) nanocapsules and their re-dispersion into water.</p> Full article ">Figure 3
<p>SEM images of polyurea (PU) nanocapsules before ((<b>a</b>) scale bar 1 μm; (<b>b</b>) scale bar 100 nm) and after redispersion ((<b>c</b>) scale bar 1 μm; (<b>d</b>) scale bar 100 nm) into 0.1 wt % SDS solution.</p> Full article ">
2911 KiB  
Article
Well-Defined Polypropylene/Polypropylene-Grafted Silica Nanocomposites: Roles of Number and Molecular Weight of Grafted Chains on Mechanistic Reinforcement
by Masahito Toyonaga, Patchanee Chammingkwan, Minoru Terano and Toshiaki Taniike
Polymers 2016, 8(8), 300; https://doi.org/10.3390/polym8080300 - 12 Aug 2016
Cited by 30 | Viewed by 7548
Abstract
Grafting terminally functionalized polypropylene (PP) to nanofillers provides well-defined PP-based nanocomposites plausibly featured with a physical cross-linkage structure. In this paper, a series of PP-grafted silica nanoparticles (PP-g-SiO2) were synthesized by varying the number of grafted chains per silica [...] Read more.
Grafting terminally functionalized polypropylene (PP) to nanofillers provides well-defined PP-based nanocomposites plausibly featured with a physical cross-linkage structure. In this paper, a series of PP-grafted silica nanoparticles (PP-g-SiO2) were synthesized by varying the number of grafted chains per silica particle, and influences of the number and the molecular weight of grafted chains were studied on physical properties of PP/PP-g-SiO2 nanocomposites. We found that only 20–30 chain/particle was sufficient to exploit benefits of the PP grafting for the nanoparticle dispersion, the nucleation, and the Young’s modulus. Meanwhile, the yield strength was sensitive to both of the number and the molecular weight of grafted PP: Grafting longer chains at a higher density led to greater reinforcement. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2016)
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<p>Schematic illustration of a physical cross-linkage structure for polypropylene (PP)/PP-grafted SiO<sub>2</sub> (PP-<span class="html-italic">g</span>-SiO<sub>2</sub>) nanocomposites.</p> Full article ">Figure 2
<p>Transmission electron microscope (TEM) images for (<b>a</b>) PP/SiO<sub>2</sub> (1 wt %); (<b>b</b>) PP/SiO<sub>2</sub> (5 wt %); (<b>c</b>) PP/120PP120-<span class="html-italic">g</span>-SiO<sub>2</sub> (1 wt %); (<b>d</b>) PP/120PP120-<span class="html-italic">g</span>-SiO<sub>2</sub> (5 wt %), and (<b>e</b>) PP/21PP120-<span class="html-italic">g</span>-SiO<sub>2</sub> (5 wt %).</p> Full article ">Figure 3
<p>Variation of the crystallization rate at 128 °C (<b>a</b>) along the chain number per particle at the fixed filler content (5.0 wt %), and (<b>b</b>) along the filler content at the fixed chain number per particle (120 chain/particle): (○,●,<math display="inline"> <semantics> <mrow> <mstyle mathcolor="#7A7A7A"> <mo>●</mo> </mstyle> </mrow> </semantics> </math>) PP/SiO<sub>2</sub>, PP/<span class="html-italic">xxx</span>PP120-<span class="html-italic">g</span>-SiO<sub>2</sub>, and PP/<span class="html-italic">xxx</span>PP<span class="html-italic">yyy</span>-<span class="html-italic">g</span>-SiO<sub>2</sub>. The data for PP/<span class="html-italic">xxx</span>PP<span class="html-italic">yyy</span>-<span class="html-italic">g</span>-SiO<sub>2</sub> is taken from Reference [<a href="#B44-polymers-08-00300" class="html-bibr">44</a>].</p> Full article ">Figure 4
<p>Wide-angle X-ray diffraction (WAXD) patterns.</p> Full article ">Figure 5
<p>Lamellar thickness distribution acquired based on the DSC endotherm in the first heating.</p> Full article ">Figure 6
<p>Stress–strain curves.</p> Full article ">Figure 7
<p>Tensile properties as a function of the chain number per particle: (<b>a</b>) Young’s modulus; (<b>b</b>) yield strength; and (<b>c</b>) elongation at break. The symbols (○,●,<math display="inline"> <semantics> <mrow> <mstyle mathcolor="#7A7A7A"> <mo>●</mo> </mstyle> </mrow> </semantics> </math>) correspond to PP/SiO<sub>2</sub>, PP/<span class="html-italic">xxx</span>PP120-<span class="html-italic">g</span>-SiO<sub>2</sub>, and PP/<span class="html-italic">xxx</span>PP<span class="html-italic">yyy</span>-<span class="html-italic">g</span>-SiO<sub>2</sub>, respectively. The data for PP/<span class="html-italic">xxx</span>PP<span class="html-italic">yyy</span>-<span class="html-italic">g</span>-SiO<sub>2</sub> is taken from Reference [<a href="#B44-polymers-08-00300" class="html-bibr">44</a>].</p> Full article ">
705 KiB  
Review
Fiber Reinforced Polymer Strengthening of Structures by Near-Surface Mounting Method
by Azadeh Parvin and Taqiuddin Syed Shah
Polymers 2016, 8(8), 298; https://doi.org/10.3390/polym8080298 - 11 Aug 2016
Cited by 44 | Viewed by 9572
Abstract
This paper provides a critical review of recent studies on strengthening of reinforced concrete and unreinforced masonry (URM) structures by fiber reinforced polymers (FRP) through near-surface mounting (NSM) method. The use of NSM-FRP has been on the rise, mainly due to composite materials’ [...] Read more.
This paper provides a critical review of recent studies on strengthening of reinforced concrete and unreinforced masonry (URM) structures by fiber reinforced polymers (FRP) through near-surface mounting (NSM) method. The use of NSM-FRP has been on the rise, mainly due to composite materials’ high strength and stiffness, non-corrosive nature and ease of installation. Experimental investigations presented in this review have confirmed the benefits associated with NSM-FRP for flexural and shear strengthening of RC and URM structures. The use of prestressing and anchorage systems to further improve NSM-FRP strain utilization and changes in failure modes has also been presented. Bond behavior of NSM-FRP-concrete or masonry interface, which is a key factor in increasing the load capacity of RC and URM structures has been briefly explored. Presented studies related to the effect of temperature on the bond performance of NSM-FRP strengthened systems with various insulations and adhesive types, show better performance than externally bonded reinforcement (EBR) FRP retrofitting. In summary, the presented literature review provides an insight into the ongoing research on the use of NSM-FRP for strengthening of structural members and the trends for future research in this area. Full article
(This article belongs to the Special Issue Selected Papers from “SMAR 2015”)
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<p>FRP strengthening (<b>a</b>) EBR FRP plate or sheet (<b>b</b>) NSM FRP rod or bar (<b>c</b>) NSM FRP laminate or strip.</p> Full article ">Figure 2
<p>NSM-FRP strengthening of beams (<b>a</b>) for flexure (<b>b</b>) for shear.</p> Full article ">Figure 3
<p>Diagonal shear test of masonry walls retrofitted with NSM FRP.</p> Full article ">
5536 KiB  
Article
Effect of Argon Plasma Treatment on Tribological Properties of UHMWPE/MWCNT Nanocomposites
by Nitturi Naresh Kumar, Seong Ling Yap, Farah Nadia Dayana Bt Samsudin, Muhammad Zubair Khan and Rama Sreekanth Pattela Srinivasa
Polymers 2016, 8(8), 295; https://doi.org/10.3390/polym8080295 - 11 Aug 2016
Cited by 41 | Viewed by 7768
Abstract
Ultra-high molecular weight polyethylene (UHMWPE) is widely used in artificial joints in the replacement of knee, hip and shoulder that has been impaired as a result of arthritis or other degenerative joint diseases. The UHMWPE made plastic cup is placed in the joint [...] Read more.
Ultra-high molecular weight polyethylene (UHMWPE) is widely used in artificial joints in the replacement of knee, hip and shoulder that has been impaired as a result of arthritis or other degenerative joint diseases. The UHMWPE made plastic cup is placed in the joint socket in contact with a metal or ceramic ball affixed to a metal stem. Effective reinforcement of multi-walled carbon nanotubes (MWCNTs) in UHMWPE results in improved mechanical and tribological properties. The hydrophobic nature of the nanocomposites surface results in lesser contact with biological fluids during the physiological interaction. In this project, we investigate the UHMWPE/MWCNTs nanocomposites reinforced with MWCNTs at different concentrations. The samples were treated with cold argon plasma at different exposure times. The water contact angles for 60 min plasma-treated nanocomposites with 0.0, 0.5, 1.0, 1.5, and 2.0 wt % MWCNTs were found to be 55.65°, 52.51°, 48.01°, 43.72°, and 37.18° respectively. Increasing the treatment time of nanocomposites has shown transformation from a hydrophobic to a hydrophilic nature due to carboxyl groups being bonded on the surface for treated nanocomposites. Wear analysis was performed under dry, and also under biological lubrication, conditions of all treated samples. The wear factor of untreated pure UHMWPE sample was reduced by 68% and 80%, under dry and lubricated conditions, respectively, as compared to 2 wt % 60 min-treated sample. The kinetic friction co-efficient was also noted under both conditions. The hardness of nanocomposites increased with both MWCNTs loading and plasma treatment time. Similarly, the surface roughness of the nanocomposites was reduced. Full article
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<p>Schematic diagram of DBD for plasma treatment of test sample.</p> Full article ">Figure 2
<p>Wettability of nanocomposites before and after plasma treatment at different time exposures.</p> Full article ">Figure 3
<p>FTIR-ATR spectra of before plasma treatment (<b>a</b>) and (<b>b</b>); 5 min plasma-treated sample (<b>c</b>) showing 2850, 2920, and 3600 peaks; and (<b>d</b>) showing 722, 1465, and 1723 peaks.</p> Full article ">Figure 4
<p>The sliding distance vs. wear volume of plasma treated samples (<b>a</b>) 10 min; (<b>b</b>) 30 min; (<b>c</b>) 60 min; (<b>d</b>) wear factor (<b>e</b>) coefficient of friction under dry test conditions.</p> Full article ">Figure 4 Cont.
<p>The sliding distance vs. wear volume of plasma treated samples (<b>a</b>) 10 min; (<b>b</b>) 30 min; (<b>c</b>) 60 min; (<b>d</b>) wear factor (<b>e</b>) coefficient of friction under dry test conditions.</p> Full article ">Figure 5
<p>Optical microscope images of test samples (2 wt % UHMWPE/MWCNT nanocomposites with 60 min plasma treatment) under dry sliding conditions showing different wear mechanisms (<b>a</b>) microcutting; (<b>b</b>) furrows; (<b>c</b>) craters; (<b>d</b>) plastic flow and deformation; (<b>e</b>) cross-wear marks and fatigue spalling; and (<b>f</b>) wear crater.</p> Full article ">Figure 6
<p>The sliding distance vs. wear volume of plasma-treated samples (<b>a</b>) 10 min; (<b>b</b>) 30 min; (<b>c</b>) 60 min; (<b>d</b>) wear factor; and (<b>e</b>) coefficient of friction, under N-Saline lubricant conditions.</p> Full article ">Figure 7
<p>Optical microscope images of test sample (2 wt % UHMWPE/MWCNT nanocomposites with 60 min plasma treatment) under N-Saline lubricant sliding conditions. (<b>a</b>) Furrows and wear direction; (<b>b</b>) cross-wear marks; (<b>c</b>) craters; and (<b>d</b>) plastic flow and deformation.</p> Full article ">Figure 8
<p>Variation of hardness of UHMWPE/MWCNTs nanocomposites under different treatment times.</p> Full article ">Figure 9
<p>Surface roughness (RMS) value of nanocomposites under dry and lubricant conditions for different treatment times.</p> Full article ">
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Article
Spatio-Temporal Proximity Characteristics in 3D ?-Printing via Multi-Photon Absorption
by Erik Hagen Waller and Georg Von Freymann
Polymers 2016, 8(8), 297; https://doi.org/10.3390/polym8080297 - 10 Aug 2016
Cited by 42 | Viewed by 7134
Abstract
One of the major challenges in high-resolution ?-printing is the cross-talk between features written in close proximity—the proximity effect. This effect prevents, e.g., gratings with periods below a few hundred nanometers. Surprisingly, the dependence of this effect on space and time has not [...] Read more.
One of the major challenges in high-resolution ?-printing is the cross-talk between features written in close proximity—the proximity effect. This effect prevents, e.g., gratings with periods below a few hundred nanometers. Surprisingly, the dependence of this effect on space and time has not thoroughly been investigated. Here, we present a spatial-light-modulator based method to dynamically measure the strength of the proximity effect on length and timescales typical to ?-printing. The proximity strength is compared in various photo resists. The results indicate that molecular diffusion strongly contributes to the proximity effect. Full article
(This article belongs to the Special Issue Three-Dimensional Structures: Fabrication and Application)
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<p>(<b>a</b>) Inset: scheme of the arrangement of the two foci. Displacement of the foci orthogonal to the writing direction by <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mi>x</mi> </mrow> </semantics> </math> and along the writing direction by <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mi>y</mi> </mrow> </semantics> </math>. One focus trails the other in time by <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mi>t</mi> <mo>=</mo> <mo>Δ</mo> <mi>y</mi> <mo>/</mo> <mi>v</mi> </mrow> </semantics> </math> with <span class="html-italic">v</span> being the writing speed. Main figure: Exemplary scanning electron micrographs of lines written in alternating writing directions with such a multi foci arrangement (indicated schematically). The linewidths <span class="html-italic">w</span> are defined and labelled according to their relative position (left focus <math display="inline"> <semantics> <mrow> <mo>→</mo> <mn>1</mn> </mrow> </semantics> </math>, right focus <math display="inline"> <semantics> <mrow> <mo>→</mo> <mn>2</mn> </mrow> </semantics> </math>, trailing along the writing direction <math display="inline"> <semantics> <mrow> <mo>→</mo> <mi mathvariant="normal">t</mi> </mrow> </semantics> </math> and leading along the writing direction <math display="inline"> <semantics> <mrow> <mo>→</mo> <mi mathvariant="normal">l</mi> </mrow> </semantics> </math>). All linewidths are found by automatic edge detection from micrographs and are individually averaged over a length of several micrometers along the middle of each line (the latter avoids non-steady-state conditions); and (<b>b</b>) edge detection method: scanning electron micrographs (pixel size <math display="inline"> <semantics> <mrow> <mn>7</mn> <mspace width="3.33333pt"/> <mi>nm</mi> <mo>)</mo> </mrow> </semantics> </math> are Fourier transformed, filtered in the Fourier domain and back transformed. Subsequently, remaining noise is removed and edges are detected by a steepest-slope approach.</p> Full article ">Figure 2
<p>Spatio-temporal characteristics of the broadening <math display="inline"> <semantics> <mrow> <mi>b</mi> <mo>=</mo> <msub> <mi>w</mi> <mi mathvariant="normal">t</mi> </msub> <mo>/</mo> <msub> <mi>w</mi> <mi mathvariant="normal">l</mi> </msub> </mrow> </semantics> </math> in the gel-like, radical based photo resist IP-G. Squares indicate the measured data, the solid line a model fit to the experimental values, and the underlay the corresponding mean-squared error. (<b>a</b>) Spatial characteristics of <span class="html-italic">b</span> for exemplary delays <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mi>t</mi> </mrow> </semantics> </math>; (<b>b</b>) temporal characteristics of <span class="html-italic">b</span> for exemplary separations <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mi>x</mi> </mrow> </semantics> </math>; (<b>c</b>) comparison of temporal characteristics of <span class="html-italic">b</span> in serial (open squares) and parallel (filled squares) writing mode; and (<b>d</b>) spatio-temporal characteristics of <span class="html-italic">b</span>.</p> Full article ">Figure 3
<p>Writing power and speed dependence of the broadening <math display="inline"> <semantics> <mrow> <mi>b</mi> <mo>=</mo> <msub> <mi>w</mi> <mi mathvariant="normal">t</mi> </msub> <mo>/</mo> <msub> <mi>w</mi> <mi mathvariant="normal">l</mi> </msub> </mrow> </semantics> </math> in IP-G. Squares indicate the measured data. The solid lines are trend lines given as a guide to the eye. (<b>a</b>) Dependence of <span class="html-italic">b</span> on incident laser power; and (<b>b</b>) dependence of <span class="html-italic">b</span> on writing speed.</p> Full article ">Figure 4
<p>Spatio-temporal characteristics of the broadening <math display="inline"> <semantics> <mrow> <mi>b</mi> <mo>=</mo> <msub> <mi>w</mi> <mi mathvariant="normal">t</mi> </msub> <mo>/</mo> <msub> <mi>w</mi> <mi mathvariant="normal">l</mi> </msub> </mrow> </semantics> </math> in the liquid, radical based photo resist IP-L. Squares indicate the measured data, the solid line a model fit to the experimental values, and the underlay the corresponding mean-squared error. (<b>a</b>) Spatial characteristics of <span class="html-italic">b</span> for exemplary delays <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mi>t</mi> </mrow> </semantics> </math>; (<b>b</b>) temporal characteristics of <span class="html-italic">b</span> for exemplary separations <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mi>x</mi> </mrow> </semantics> </math>; (<b>c</b>) spatio-temporal characteristics of <span class="html-italic">b</span>; and (<b>d</b>) comparison of the temporal characteristics of <span class="html-italic">b</span> in SU-8 (open squares) and IP-G (filled squares) for exemplary values of <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mi>x</mi> </mrow> </semantics> </math>.</p> Full article ">Figure 5
<p>Radical diffusion scheme. <b>Left</b>: the leading line affects the trailing line. Radicals diffuse from various positions on the leading line (<b>red</b> circles) to position 1 (marked by the <b>black</b> 1). The <b>white</b> lines denote the diffusion distance which changes over time. The lines indicate diffusion prior to the trailing spot reaching position 1. It follows from the figure: <math display="inline"> <semantics> <mrow> <msubsup> <mi>r</mi> <mi>lt</mi> <mn>2</mn> </msubsup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mo>Δ</mo> <msup> <mi>x</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <mo>Δ</mo> <mi>y</mi> <mo>-</mo> <mi>v</mi> <mi>t</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </mrow> </semantics> </math> (<span class="html-italic">v</span> is the writing speed). <math display="inline"> <semantics> <msub> <mi>t</mi> <mi mathvariant="normal">w</mi> </msub> </semantics> </math> is the total writing time. <b>Right</b>: the same as the left but indicating how the trailing line affects the leading line. Here, we find: <math display="inline"> <semantics> <mrow> <msubsup> <mi>r</mi> <mi>tl</mi> <mn>2</mn> </msubsup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mo>Δ</mo> <msup> <mi>x</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <mi>v</mi> <mi>t</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </mrow> </semantics> </math>.</p> Full article ">Figure 6
<p>Effective diffusion constant determined from the fits. (<b>a</b>) Dependence of the constant on the line separation in IP-L and IP-G. The <b>grey</b> area indicates the spatial extent (full-width-half-maximum) of the excitation focus; and (<b>b</b>) dependence of the constant on the time delay in IP-G. The <b>red</b> line is an exponential fit to the data excluding the values at <math display="inline"> <semantics> <mrow> <mn>4</mn> <mspace width="3.33333pt"/> <mi>ms</mi> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mn>100</mn> <mspace width="3.33333pt"/> <mi>ms</mi> </mrow> </semantics> </math>. The inset shows a log-plot of the data.</p> Full article ">Figure 7
<p>Oxygen diffusion model fitted to the experimental data. The calculation is done on a discretized grid and no smoothing is applied.</p> Full article ">
1771 KiB  
Review
Semiflexible Polymers in the Bulk and Confined by Planar Walls
by Sergei A. Egorov, Andrey Milchev and Kurt Binder
Polymers 2016, 8(8), 296; https://doi.org/10.3390/polym8080296 - 10 Aug 2016
Cited by 27 | Viewed by 6161
Abstract
Semiflexible polymers in solution under good solvent conditions can undergo an isotropic-nematic transition. This transition is reminiscent of the well-known entropically-driven transition of hard rods described by Onsager’s theory, but the flexibility of the macromolecules causes specific differences in behavior, such as anomalous [...] Read more.
Semiflexible polymers in solution under good solvent conditions can undergo an isotropic-nematic transition. This transition is reminiscent of the well-known entropically-driven transition of hard rods described by Onsager’s theory, but the flexibility of the macromolecules causes specific differences in behavior, such as anomalous long wavelength fluctuations in the ordered phase, which can be understood by the concept of the deflection length. A brief review of the recent progress in the understanding of these problems is given, summarizing results obtained by large-scale molecular dynamics simulations and density functional theory. These results include also the interaction of semiflexible polymers with hard walls and the wall-induced nematic order, which can give rise to capillary nematization in thin film geometry. Various earlier theoretical approaches to these problems are briefly mentioned, and an outlook on the status of experiments is given. It is argued that in many cases of interest, it is not possible to describe the scaled densities at the isotropic-nematic transition as functions of the ratio of the contour length and the persistence length alone, but the dependence on the ratio of chain diameter and persistence length also needs to be considered. Full article
(This article belongs to the Special Issue Semiflexible Polymers)
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Full article ">Figure 1
<p>(<b>a</b>) Pressure <span class="html-italic">P</span> vs. density <span class="html-italic">ρ</span> for semiflexible chains with <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math> beads and <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>128</mn> </mrow> </semantics> </math>. Due to the choice of units <math display="inline"> <semantics> <mrow> <mi>σ</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>ϵ</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mi>B</mi> </msub> <mi>T</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math>, both <span class="html-italic">P</span> and <span class="html-italic">ρ</span> are dimensionless. Circles represent MD data, while curves denote the corresponding DFT-CS and DFT-GFD predictions, as indicated. Open squares and crosses indicate coexistence conditions; (<b>b</b>) Same as (a), but for <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>128</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math>; (<b>c</b>) Order parameter as a function of density for semiflexible chains of length <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math> and various choices of <math display="inline"> <semantics> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> </semantics> </math>, as indicated. Circles are MD results, curves are DFT-CS predictions for <math display="inline"> <semantics> <mrow> <mi>S</mi> <mo stretchy="false">(</mo> <mi>ρ</mi> <mo stretchy="false">)</mo> </mrow> </semantics> </math>, ending at <math display="inline"> <semantics> <mrow> <mi>S</mi> <mrow> <mo stretchy="false">(</mo> <msub> <mi>ρ</mi> <mi>n</mi> </msub> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <msub> <mi>S</mi> <mi>c</mi> </msub> </mrow> </semantics> </math> (diamonds), while the linear variation in the I-N coexistence region is shown by dashed straight lines. The corresponding predictions from Chen [<a href="#B20-polymers-08-00296" class="html-bibr">20</a>] for the I-N coexistence region are shown by dotted straight lines, ending in squares; (<b>d</b>) Same as (c), but for <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>64</mn> </mrow> </semantics> </math>. Reproduced from [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>] with permission from the Royal Society of Chemistry.</p> Full article ">Figure 2
<p>(<b>a</b>) Predictions for the I-N transition densities from [<a href="#B20-polymers-08-00296" class="html-bibr">20</a>] compared to MD and DFT results [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>], in a log-log plot of inverse persistence length vs. density. Different symbols and different colors indicate the different chain lengths <span class="html-italic">N</span> = 8, 16, 32 and 64, respectively, as indicated in the key. The I-N coexistence regions predicted by Chen [<a href="#B20-polymers-08-00296" class="html-bibr">20</a>] are shown as shaded regions, while DFT-CS results are shown as curves, and symbols are Monte Carlo simulations (diamonds [<a href="#B49-polymers-08-00296" class="html-bibr">49</a>]) and MD simulations (circles [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>]), respectively. Here, MD data show as a simple transition density <math display="inline"> <semantics> <msub> <mi>ρ</mi> <mi>tr</mi> </msub> </semantics> </math> the inflection points of the <span class="html-italic">S</span> vs. <span class="html-italic">ρ</span> curves; (<b>b</b>) Same as (a), but choosing density and chain length <span class="html-italic">N</span> as variables. As in (a), shaded stripes are the two-phase coexistence regions predicted by Chen [<a href="#B20-polymers-08-00296" class="html-bibr">20</a>], full curves DFT-CS and symbols the MD data [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>], for several choices of <math display="inline"> <semantics> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> </semantics> </math>: <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>8</mn> </mrow> </semantics> </math> (blue); <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>16</mn> </mrow> </semantics> </math> (green); <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math> (red); <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>100</mn> </mrow> </semantics> </math> (purple, MD); <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>128</mn> </mrow> </semantics> </math> (purple, DFT-CS). Reproduced from [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>] with permission from the Royal Society of Chemistry.</p> Full article ">Figure 3
<p>(<b>a</b>) Transition densities scaled as <math display="inline"> <semantics> <mrow> <msub> <mi>ρ</mi> <mi>i</mi> </msub> <mi>π</mi> <mi>N</mi> <mo>/</mo> <mn>4</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <msub> <mi>ρ</mi> <mi>n</mi> </msub> <mi>π</mi> <mi>N</mi> <mo>/</mo> <mn>4</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <msub> <mi>ρ</mi> <mi>tr</mi> </msub> <mi>π</mi> <mi>N</mi> <mo>/</mo> <mn>4</mn> </mrow> </semantics> </math> plotted vs. <math display="inline"> <semantics> <mrow> <mi>d</mi> <mo>/</mo> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> </mrow> </semantics> </math> (using units where <math display="inline"> <semantics> <mrow> <mi>d</mi> <mo>=</mo> <mi>σ</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math>), for four choices of <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>/</mo> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> </mrow> </semantics> </math>, distinguished by color: <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>/</mo> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>2</mn> </mrow> </semantics> </math> (blue); <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>/</mo> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> <mo>=</mo> <mspace width="3.33333pt"/> <mn>1</mn> </mrow> </semantics> </math> (green); <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>/</mo> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> </mrow> </semantics> </math> (red); <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>/</mo> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>25</mn> </mrow> </semantics> </math> (purple). Symbols are the MD results; full curves denote DFT-CS predictions [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>]; while the horizontal shaded stripes show the I-N coexistence regions from [<a href="#B20-polymers-08-00296" class="html-bibr">20</a>]. Note that <math display="inline"> <semantics> <mrow> <mi>ρ</mi> <mi>L</mi> <mo>/</mo> <mi>d</mi> <mo>=</mo> <mrow> <mo stretchy="false">(</mo> <mi>ρ</mi> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> <mo>/</mo> <mi>d</mi> <mo stretchy="false">)</mo> </mrow> <mi>L</mi> <mo>/</mo> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> </mrow> </semantics> </math> is plotted here rather than <math display="inline"> <semantics> <mrow> <mi>ρ</mi> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> <mo>/</mo> <mi>d</mi> </mrow> </semantics> </math> discussed in the text, to avoid cluttering the figure, and the factor <math display="inline"> <semantics> <mrow> <mi>π</mi> <mo>/</mo> <mn>4</mn> </mrow> </semantics> </math> accounts for the normalization of the density with the cylinder volume <math display="inline"> <semantics> <mrow> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> <msup> <mi>d</mi> <mn>2</mn> </msup> <mi>π</mi> <mo>/</mo> <mn>4</mn> </mrow> </semantics> </math> as in the Onsager theory; (<b>b</b>) Transition density <math display="inline"> <semantics> <mrow> <msub> <mi>ρ</mi> <mi>i</mi> </msub> <mi>π</mi> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> <mo>/</mo> <mrow> <mo stretchy="false">(</mo> <mn>4</mn> <mi>d</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> plotted vs <math display="inline"> <semantics> <msubsup> <mi>ℓ</mi> <mi>p</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> </semantics> </math>, comparing MD data to the theories of Chen [<a href="#B20-polymers-08-00296" class="html-bibr">20</a>], Odijk [<a href="#B16-polymers-08-00296" class="html-bibr">16</a>], Khokhlov and Semenov [<a href="#B12-polymers-08-00296" class="html-bibr">12</a>,<a href="#B13-polymers-08-00296" class="html-bibr">13</a>], scaled particle theory (SPT) [<a href="#B18-polymers-08-00296" class="html-bibr">18</a>,<a href="#B21-polymers-08-00296" class="html-bibr">21</a>], DFT-CS, DFT-generalized Flory dimer (GFD) and the DuPré–Yang theory [<a href="#B19-polymers-08-00296" class="html-bibr">19</a>], as indicated in the key. Reproduced from [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>] with permission from the Royal Society of Chemistry.</p> Full article ">Figure 4
<p>(<b>a</b>) Snapshot of a system of semiflexible polymers with length <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math>, stiffness <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>100</mn> </mrow> </semantics> </math>, at concentration <math display="inline"> <semantics> <mrow> <mi>ρ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>6</mn> </mrow> </semantics> </math> (with nematic order parameter <math display="inline"> <semantics> <mrow> <mi>S</mi> <mo>≈</mo> <mn>0</mn> <mo>.</mo> <mn>9</mn> </mrow> </semantics> </math>). Chains are shown in different colors so that they can be better distinguished visually; (<b>b</b>) Typical conformation of a semiflexible polymer in the nematic phase (<math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>64</mn> <mo>,</mo> <mspace width="0.277778em"/> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>16</mn> <mo>,</mo> <mspace width="0.277778em"/> <mi>ρ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>4</mn> <mo>,</mo> <mspace width="0.277778em"/> <mi>S</mi> <mo>≈</mo> <mn>0</mn> <mo>.</mo> <mn>9</mn> </mrow> </semantics> </math>); (<b>c</b>) Schematic description of nematic order as effective cylindrical confinement: each chain has its own cylindrical bent tube of diameter <math display="inline"> <semantics> <mrow> <mn>2</mn> <msub> <mi>r</mi> <mi>ρ</mi> </msub> </mrow> </semantics> </math> defined such that it contains only monomers from the considered chain. This tube roughly follows the contour of this macromolecule, which shows long wavelength undulations with a typical wavelength given by the deflection length. The typical amplitude of these deflections is of the order <math display="inline"> <semantics> <msub> <mi>r</mi> <mi>eff</mi> </msub> </semantics> </math> defining a cylinder (the straight axis of this cylinder is oriented along the director of the nematic phase). This cylinder contains not only a single bent tube, but rather is densely filled by a whole bundle of neighboring tubes whose deflections are strongly correlated. Reproduced from [<a href="#B42-polymers-08-00296" class="html-bibr">42</a>] with permission from the APS.</p> Full article ">Figure 5
<p>(<b>a</b>) Local order parameter <math display="inline"> <semantics> <msub> <mi>S</mi> <mi>i</mi> </msub> </semantics> </math> that describes the orientation of the bond connecting monomers at <math display="inline"> <semantics> <msub> <mi mathvariant="bold">r</mi> <mi>i</mi> </msub> </semantics> </math> and <math display="inline"> <semantics> <msub> <mi mathvariant="bold">r</mi> <mrow> <mi>i</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> </semantics> </math> (the free ends being <math display="inline"> <semantics> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>i</mi> <mo>=</mo> <mi>N</mi> </mrow> </semantics> </math>, and all equivalent bonds in the system are averaged over) plotted versus <math display="inline"> <semantics> <mrow> <mi>i</mi> <mo>/</mo> <mi>N</mi> </mrow> </semantics> </math> for <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> </mrow> </semantics> </math>128, the total number of monomers being <math display="inline"> <semantics> <mrow> <mi>N</mi> <mi mathvariant="script">N</mi> <mo>=</mo> </mrow> </semantics> </math> 460,800, for three choices of <math display="inline"> <semantics> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> </semantics> </math>: <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>/</mo> <msub> <mi>k</mi> <mi>B</mi> </msub> <mi>T</mi> <mo>=</mo> <mn>128</mn> <mo>,</mo> <mspace width="0.277778em"/> <mi>ρ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>1</mn> <mo>;</mo> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>/</mo> <msub> <mi>k</mi> <mi>N</mi> </msub> <mi>T</mi> <mo>=</mo> <mn>64</mn> <mo>,</mo> <mspace width="0.277778em"/> <mi>ρ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>16</mn> </mrow> </semantics> </math>; <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>/</mo> <msub> <mi>k</mi> <mi>B</mi> </msub> <mi>T</mi> <mo>=</mo> <mn>32</mn> <mo>,</mo> <mspace width="0.277778em"/> <mi>ρ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>25</mn> </mrow> </semantics> </math>. The densities were chosen such that the nematic order parameter <span class="html-italic">S</span> is close to 0.7 in each case. The three choices of the parameter <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>/</mo> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> </mrow> </semantics> </math> (which roughly corresponds to <math display="inline"> <semantics> <mrow> <mi>L</mi> <mo>/</mo> <msub> <mi>ℓ</mi> <mi>p</mi> </msub> </mrow> </semantics> </math>) are indicated in the key. The inset shows a semi-log plot of <math display="inline"> <semantics> <msub> <mi>S</mi> <mi>∞</mi> </msub> </semantics> </math>-<math display="inline"> <semantics> <msub> <mi>S</mi> <mi>i</mi> </msub> </semantics> </math> vs. <span class="html-italic">i</span> to test Equation (<a href="#FD31-polymers-08-00296" class="html-disp-formula">31</a>). The resulting values of <span class="html-italic">λ</span> are 8.2, 3.65 and 2.36, respectively; (<b>b</b>) Effective cylinder radius <math display="inline"> <semantics> <msub> <mi>r</mi> <mi>eff</mi> </msub> </semantics> </math> plotted vs. density <span class="html-italic">ρ</span>, for <span class="html-italic">N</span> = 128, and two choices of <math display="inline"> <semantics> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> </semantics> </math>: <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>64</mn> </mrow> </semantics> </math> and 128, as indicated in the key. Furthermore, the radius <math display="inline"> <semantics> <msub> <mi>r</mi> <mi>ρ</mi> </msub> </semantics> </math> (Equation (<a href="#FD27-polymers-08-00296" class="html-disp-formula">27</a>); cf. <a href="#polymers-08-00296-f004" class="html-fig">Figure 4</a>c) is included for comparison. The inset shows a plot of the transverse mean-square displacements <math display="inline"> <semantics> <mrow> <mo stretchy="false">〈</mo> <msubsup> <mi>r</mi> <mrow> <mi>⊥</mi> </mrow> <mn>2</mn> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi>i</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">〉</mo> </mrow> </semantics> </math>, relative to the end-to-end vector of the chain, as a function of <span class="html-italic">i</span>, for <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>128</mn> </mrow> </semantics> </math> at two densities, as indicated. Equation (<a href="#FD28-polymers-08-00296" class="html-disp-formula">28</a>) implies that <math display="inline"> <semantics> <mrow> <mo stretchy="false">〈</mo> <msubsup> <mi>r</mi> <mrow> <mi>⊥</mi> </mrow> <mn>2</mn> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi>i</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">〉</mo> </mrow> </semantics> </math> increases linearly with <span class="html-italic">i</span> and saturates at <math display="inline"> <semantics> <mrow> <mi>i</mi> <mo>≈</mo> <mi>λ</mi> </mrow> </semantics> </math> with <math display="inline"> <semantics> <mrow> <mrow> <mo stretchy="false">〈</mo> <msubsup> <mi>r</mi> <mrow> <mi>⊥</mi> </mrow> <mn>2</mn> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi>i</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">〉</mo> </mrow> <mo>≈</mo> <mspace width="3.33333pt"/> <msup> <mrow> <mo stretchy="false">(</mo> <msub> <mi>r</mi> <mi>eff</mi> </msub> <mo>/</mo> <mi>λ</mi> <mo stretchy="false">)</mo> </mrow> <mn>2</mn> </msup> </mrow> </semantics> </math>. The data points for <math display="inline"> <semantics> <msub> <mi>r</mi> <mi>eff</mi> </msub> </semantics> </math> are extracted from these maximum transverse displacements, and the estimates extracted from Equation (<a href="#FD29-polymers-08-00296" class="html-disp-formula">29</a>) are included for comparison. Reproduced from [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>] with permission from the Royal Society of Chemistry.</p> Full article ">Figure 6
<p>Plot of the order parameter reduction <math display="inline"> <semantics> <mrow> <mn>1</mn> <mo>-</mo> <mi>S</mi> </mrow> </semantics> </math> versus the relative reduction of the end-to-end distance <math display="inline"> <semantics> <mrow> <mn>1</mn> <mo>-</mo> <msup> <mrow> <mo stretchy="false">〈</mo> <msubsup> <mi>R</mi> <mrow> <mi>e</mi> </mrow> <mn>2</mn> </msubsup> <mo stretchy="false">〉</mo> </mrow> <mrow> <mn>1</mn> <mo>/</mo> <mn>2</mn> </mrow> </msup> <mo>/</mo> <mi>L</mi> </mrow> </semantics> </math>. Three choices of the chain length <span class="html-italic">N</span> (<math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> <mo>,</mo> <mspace width="0.277778em"/> <mn>64</mn> </mrow> </semantics> </math> and 128), and in each case, three choices of the parameter <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>/</mo> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>1</mn> <mo>,</mo> <mspace width="0.277778em"/> <mn>2</mn> </mrow> </semantics> </math> and 4 are included, as indicated in the key. The straight line indicates Equation (<a href="#FD29-polymers-08-00296" class="html-disp-formula">29</a>). Reproduced from [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>] with permission from the Royal Society of Chemistry.</p> Full article ">Figure 7
<p>(<b>a</b>) Monomer density profiles <math display="inline"> <semantics> <mrow> <mi>ρ</mi> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </semantics> </math> across the film for <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>=</mo> <mn>40</mn> </mrow> </semantics> </math> and four values of the stiffness parameter <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>1</mn> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>10</mn> </mrow> </semantics> </math> and 30, choosing <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>ρ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>1</mn> </mrow> </semantics> </math> in the MD simulation. The MD profiles are the noisy curves, while the corresponding DFT calculations were done choosing a chemical potential for which the bulk density <math display="inline"> <semantics> <msub> <mi>ρ</mi> <mi>b</mi> </msub> </semantics> </math> coincides with the density <math display="inline"> <semantics> <msub> <mi>ρ</mi> <mi>middle</mi> </msub> </semantics> </math> in the middle of the film, at <math display="inline"> <semantics> <mrow> <mi>z</mi> <mo>=</mo> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>/</mo> <mn>2</mn> </mrow> </semantics> </math>. These densities <math display="inline"> <semantics> <msub> <mi>ρ</mi> <mi>middle</mi> </msub> </semantics> </math> are quoted in the key of the figure, and the smooth lines show the DFT profiles. Note that the curves are shifted vertically by 0.015 relative to each other for the sake of better visibility; (<b>b</b>) Surface tension <span class="html-italic">γ</span> (Equation (<a href="#FD22-polymers-08-00296" class="html-disp-formula">22</a>)) plotted vs. <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>/</mo> <msub> <mi>k</mi> <mi>B</mi> </msub> <mi>T</mi> </mrow> </semantics> </math> for the case <math display="inline"> <semantics> <mrow> <msub> <mi>ρ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>1</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math>, comparing MD results (dots) with DFT predictions (line); (<b>c</b>) Same as (b), but for the case <math display="inline"> <semantics> <mrow> <msub> <mi>ρ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>0625</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>16</mn> </mrow> </semantics> </math> (upper part) and <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>100</mn> </mrow> </semantics> </math> (lower part), plotted vs. chain length <span class="html-italic">N</span>. The contributions of the isotropic and orientational terms are shown as broken and dash-dotted curves, respectively. Reproduced from [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>] with the permission of AIP Publishing.</p> Full article ">Figure 7 Cont.
<p>(<b>a</b>) Monomer density profiles <math display="inline"> <semantics> <mrow> <mi>ρ</mi> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </semantics> </math> across the film for <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>=</mo> <mn>40</mn> </mrow> </semantics> </math> and four values of the stiffness parameter <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>1</mn> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>10</mn> </mrow> </semantics> </math> and 30, choosing <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>ρ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>1</mn> </mrow> </semantics> </math> in the MD simulation. The MD profiles are the noisy curves, while the corresponding DFT calculations were done choosing a chemical potential for which the bulk density <math display="inline"> <semantics> <msub> <mi>ρ</mi> <mi>b</mi> </msub> </semantics> </math> coincides with the density <math display="inline"> <semantics> <msub> <mi>ρ</mi> <mi>middle</mi> </msub> </semantics> </math> in the middle of the film, at <math display="inline"> <semantics> <mrow> <mi>z</mi> <mo>=</mo> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>/</mo> <mn>2</mn> </mrow> </semantics> </math>. These densities <math display="inline"> <semantics> <msub> <mi>ρ</mi> <mi>middle</mi> </msub> </semantics> </math> are quoted in the key of the figure, and the smooth lines show the DFT profiles. Note that the curves are shifted vertically by 0.015 relative to each other for the sake of better visibility; (<b>b</b>) Surface tension <span class="html-italic">γ</span> (Equation (<a href="#FD22-polymers-08-00296" class="html-disp-formula">22</a>)) plotted vs. <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>/</mo> <msub> <mi>k</mi> <mi>B</mi> </msub> <mi>T</mi> </mrow> </semantics> </math> for the case <math display="inline"> <semantics> <mrow> <msub> <mi>ρ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>1</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math>, comparing MD results (dots) with DFT predictions (line); (<b>c</b>) Same as (b), but for the case <math display="inline"> <semantics> <mrow> <msub> <mi>ρ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>0625</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>16</mn> </mrow> </semantics> </math> (upper part) and <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>100</mn> </mrow> </semantics> </math> (lower part), plotted vs. chain length <span class="html-italic">N</span>. The contributions of the isotropic and orientational terms are shown as broken and dash-dotted curves, respectively. Reproduced from [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>] with the permission of AIP Publishing.</p> Full article ">Figure 8
<p>Normalized end-monomer (upper part) and mid-monomer (lower part) density profiles, <math display="inline"> <semantics> <mrow> <mn>2</mn> <mi>N</mi> <msub> <mi>ρ</mi> <mi>end</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> <mo>/</mo> <msub> <mi>ρ</mi> <mi>b</mi> </msub> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mn>2</mn> <mi>N</mi> <msub> <mi>ρ</mi> <mi>mid</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> <mo>/</mo> <msub> <mi>ρ</mi> <mi>b</mi> </msub> </mrow> </semantics> </math>, plotted vs. <span class="html-italic">z</span>, for the case <math display="inline"> <semantics> <msub> <mi>ρ</mi> <mi>b</mi> </msub> </semantics> </math> = 0.1, <span class="html-italic">N</span> = 32, and several choices of <math display="inline"> <semantics> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> </semantics> </math>, as indicated in the key. Reproduced from [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>] with the permission of AIP Publishing.</p> Full article ">Figure 9
<p>(<b>a</b>) Plot of the local order <math display="inline"> <semantics> <mrow> <mi>S</mi> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </semantics> </math> vs. <span class="html-italic">z</span> for the case <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>8</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>100</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>=</mo> <mn>100</mn> </mrow> </semantics> </math>, where <math display="inline"> <semantics> <msub> <mi>ρ</mi> <mi>tr</mi> </msub> </semantics> </math> = 0.55, as obtained from MD; (<b>b</b>) Plot of the surface excess order parameter <math display="inline"> <semantics> <mrow> <mrow> <mo>|</mo> </mrow> <msub> <mi mathvariant="normal">Ψ</mi> <mi>s</mi> </msub> <mrow> <mo>|</mo> </mrow> </mrow> </semantics> </math>, with <math display="inline"> <semantics> <mrow> <msub> <mi mathvariant="normal">Ψ</mi> <mi>s</mi> </msub> <mo>=</mo> <msubsup> <mo>∫</mo> <mrow> <mn>0</mn> </mrow> <mrow> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>/</mo> <mn>2</mn> </mrow> </msubsup> <mi>d</mi> <mi>z</mi> <mi>S</mi> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math>, vs. <math display="inline"> <semantics> <mrow> <msub> <mi>ρ</mi> <mi>tr</mi> </msub> <mo>-</mo> <mi>ρ</mi> </mrow> </semantics> </math>, for the case <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>16</mn> </mrow> </semantics> </math>, where <math display="inline"> <semantics> <msub> <mi>ρ</mi> <mi>tr</mi> </msub> </semantics> </math> = 0.30, using data for <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>=</mo> <mn>40</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>=</mo> <mn>100</mn> </mrow> </semantics> </math> (to check for finite size effects) and displaying data for <math display="inline"> <semantics> <msub> <mi mathvariant="normal">Ψ</mi> <mi>s</mi> </msub> </semantics> </math> extracted from the range from <math display="inline"> <semantics> <mrow> <mi>z</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math> to <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>/</mo> <mn>2</mn> </mrow> </semantics> </math>, as well as from <math display="inline"> <semantics> <mrow> <mi>z</mi> <mo>=</mo> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>/</mo> <mn>2</mn> </mrow> </semantics> </math> to <math display="inline"> <semantics> <msub> <mi>L</mi> <mi>z</mi> </msub> </semantics> </math>, to illustrate the large statistical scatter. The straight line illustrates the fit to a logarithmic variation, <math display="inline"> <semantics> <mrow> <mrow> <mo>|</mo> </mrow> <msub> <mi mathvariant="normal">Ψ</mi> <mi>s</mi> </msub> <mrow> <mo>|</mo> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>36</mn> <mo>-</mo> <mn>0</mn> <mo>.</mo> <mn>79</mn> <mo form="prefix">ln</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <msub> <mi>ρ</mi> <mi>tr</mi> </msub> <mo>-</mo> <mi>ρ</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math>. Reproduced from [<a href="#B43-polymers-08-00296" class="html-bibr">43</a>] with the permission of AIP Publishing.</p> Full article ">Figure 10
<p>Plot of the layer-resolved director as a function of the <span class="html-italic">z</span>-coordinate across the film for the case <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi mathvariant="script">N</mi> <mo>=</mo> <mn>1500</mn> </mrow> </semantics> </math> chains, <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>=</mo> <mn>40</mn> <mo>,</mo> <mspace width="0.277778em"/> <mi>Δ</mi> <mi>z</mi> <mo>=</mo> <mn>1</mn> <mo>.</mo> <mn>0</mn> </mrow> </semantics> </math>, and the densities <math display="inline"> <semantics> <mrow> <mi>ρ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>1</mn> </mrow> </semantics> </math> (<b>a</b>); <math display="inline"> <semantics> <mrow> <mi>ρ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>2</mn> </mrow> </semantics> </math> (<b>b</b>); and <math display="inline"> <semantics> <mrow> <mi>ρ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>3</mn> </mrow> </semantics> </math> (<b>c</b>). The arrows show the orientations of the corresponding 40 unit vectors for each value of <span class="html-italic">z</span>. Note the different scales for <span class="html-italic">X</span>-, <span class="html-italic">Y</span>- and <span class="html-italic">Z</span>-directions. Reproduced from [<a href="#B45-polymers-08-00296" class="html-bibr">45</a>] with the permission of Wiley-VCH.</p> Full article ">Figure 11
<p>Thermally-averaged order parameter profile <math display="inline"> <semantics> <mrow> <msub> <mi>λ</mi> <mo>+</mo> </msub> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> vs. distance <span class="html-italic">z</span> for the case <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> <mo>,</mo> <mspace width="0.277778em"/> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>32</mn> <mo>,</mo> <mspace width="0.277778em"/> </mrow> </semantics> </math> <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi>z</mi> </msub> <mo>=</mo> <mn>40</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi mathvariant="script">N</mi> <mo>=</mo> <mn>1500</mn> </mrow> </semantics> </math> and various densities, as indicated. Note that in the bulk, the I-N transition occurs at <math display="inline"> <semantics> <mrow> <msub> <mi>ρ</mi> <mi>tr</mi> </msub> <mo>≈</mo> <mn>0</mn> <mo>.</mo> <mn>30</mn> </mrow> </semantics> </math>. Reproduced from [<a href="#B45-polymers-08-00296" class="html-bibr">45</a>] with the permission of Wiley-VCH.</p> Full article ">Figure 12
<p>(<b>a</b>) DFT results for the nematic order parameter <span class="html-italic">S</span> as a function of the dimensionless chemical potential <span class="html-italic">μ</span> for <math display="inline"> <semantics> <mrow> <msub> <mi>ϵ</mi> <mi>b</mi> </msub> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>32</mn> </mrow> </semantics> </math> and several choices of <math display="inline"> <semantics> <msub> <mi>L</mi> <mi>z</mi> </msub> </semantics> </math>, as indicated. The bulk behavior is included (the vertical broken line indicates the transition in the bulk); (<b>b</b>) Inverse response function <math display="inline"> <semantics> <msup> <mrow> <mo stretchy="false">[</mo> <mi>d</mi> <mi>S</mi> <mrow> <mo stretchy="false">(</mo> <mi>μ</mi> <mo stretchy="false">)</mo> </mrow> <mo>/</mo> <mi>d</mi> <mi>μ</mi> <mo stretchy="false">]</mo> </mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </semantics> </math> plotted vs. <span class="html-italic">μ</span> for the same case as (a). Reproduced from [<a href="#B45-polymers-08-00296" class="html-bibr">45</a>] with the permission of Wiley-VCH.</p> Full article ">
6759 KiB  
Article
Optimized Synthesis According to One-Step Process of a Biobased Thermoplastic Polyacetal Derived from Isosorbide
by Nadia Hammami, Nathalie Jarroux, Mike Robitzer, Mustapha Majdoub and Jean-Pierre Habas
Polymers 2016, 8(8), 294; https://doi.org/10.3390/polym8080294 - 10 Aug 2016
Cited by 13 | Viewed by 8534
Abstract
This paper describes both the synthesis and characterization of a biobased and non-aromatic polyacetal produced from the reaction between isosorbide and methylene chloride. The reaction was conducted in an aprotic dipolar and harmless solvent using a one-step, fast and economical procedure. The chemical [...] Read more.
This paper describes both the synthesis and characterization of a biobased and non-aromatic polyacetal produced from the reaction between isosorbide and methylene chloride. The reaction was conducted in an aprotic dipolar and harmless solvent using a one-step, fast and economical procedure. The chemical composition of this polymer was investigated using Nuclear Magnetic Resonance and Fourier Transform Infra-Red spectroscopies. The molecular weights were examined by size exclusion chromatography and MALDI-TOF spectrometry. The synthesis conditions (concentration, mixing speed, solvent nature, stoichiometry, addition mode of one reactan) were found to strongly influence both polymer architecture and reaction yield. Under moderated stirring conditions, the polyacetal was characterized by a larger amount of macro-cycles. Inversely, under higher intensity mixing and with an excess of methylene chloride, it was mainly composed of linear chains. In this latter case, the polymeric material presented an amorphous morphology with a glass transition temperature (Tg) close to 55 °C. Its degradation temperature was evaluated to be close to 215 °C using thermogravimetry according to multi-ramp methodology. The chemical approach and the physicochemical properties are valuable in comparison with that characteristic of other isosorbide-based polyacetals. Full article
(This article belongs to the Special Issue Renewable Polymeric Adhesives)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Different routes described in literature for polyacetals synthesis where R is an aliphatic or aromatic sequence and X is given for Cl or Br.</p> Full article ">Figure 2
<p>Chemical structures of dianhydrohexitols: isosorbide (IS), isoidide (II) and isomannide (IM).</p> Full article ">Figure 3
<p>Influence of the stirring method on the reaction yield between isosorbide and methylene chloride.</p> Full article ">Figure 4
<p>Comparison of FTIR spectra of PAIS and original IS (shifted along vertical axis for easier identification).</p> Full article ">Figure 5
<p>Synthesis of polyacetal obtained from the reaction between isosorbide and methylene chloride. L: Linear structure of PAIS; C: Circular structure of PAIS.</p> Full article ">Figure 6
<p><sup>1</sup>H NMR spectrum of PAIS based on isosorbide, registered in CDCl<sub>3</sub>.</p> Full article ">Figure 7
<p><sup>13</sup>C NMR spectrum of PAIS based on isosorbide as registered in DMSO-d<sub>6</sub>.</p> Full article ">Figure 8
<p>Example of representation of chemical structure of polyacetal based on isosorbide.</p> Full article ">Figure 9
<p>MALDI-TOF mass spectrum of PAIS (<span class="html-italic">C</span> = 2 M) prepared under high intensity mixing. Linear chains cationized with K<sup>+</sup> or Na<sup>+</sup> are represented by △ and ▲ symbols, respectively. Cyclic species cationized with K<sup>+</sup> or Na<sup>+</sup> are depicted by Ο and ●, respectively.</p> Full article ">Figure 10
<p>MALDI-TOF mass spectrum of PAIS prepared under high intensity mixing and with high concentration (<span class="html-italic">C</span> = 2.6 M). The attribution of the symbols is unchanged compared to <a href="#polymers-08-00294-f009" class="html-fig">Figure 9</a>.</p> Full article ">Figure 11
<p>Focus on MALDI-TOF mass spectrum of PAIS prepared under high intensity mixing (2.6 M). Linear chains cationized with K<sup>+</sup> or Na<sup>+</sup> are represented by △ and ▲ symbols, respectively. Cyclic species cationized with K<sup>+</sup> or Na<sup>+</sup> are depicted by Ο and ●, respectively.</p> Full article ">Figure 12
<p>Representation of chemical structure of chloromethyl ether isosorbide intermediate.</p> Full article ">Figure 13
<p>SEC analysis of PAIS synthesized for <span class="html-italic">C</span> = 2 M under magnetic stirring. Dashed line: deconvolution based on three individual Gaussian distributions.</p> Full article ">Figure 14
<p>SEC analysis of PAIS synthesized for <span class="html-italic">C</span> = 2M under mechanical stirring. Dashed line: deconvolution based on three individual Gaussian distributions.</p> Full article ">Figure 15
<p>Influence of the initial concentration of isosorbide on the SEC analysis of PAIS.</p> Full article ">Figure 16
<p>Deconvolution of SEC analyses of PAIS prepared with <span class="html-italic">C</span> = 1 M (<b>left</b>) and <span class="html-italic">C</span> = 2.6 M (<b>right</b>).</p> Full article ">Figure 17
<p>DSC thermogram of linear PAIS produced from the synthesis between isosorbide (<span class="html-italic">C</span> = 2.6 M) and methylene chloride using high-speed stirring.</p> Full article ">Figure 18
<p>Influence of the heating ramp on the PAIS thermogravimetric profile recorded from 0 to 600 °C under air. Insert: evaluation of the real degradation temperature (the dotted curve is given as a guide).</p> Full article ">Figure 19
<p>MALDI-TOF mass spectrum of PAIS (<span class="html-italic">C</span> = 1 M) prepared under magnetic mixing. Linear chains are represented by triangular symbols (△) while cyclic species are characterized by circular symbols (Ο), both cationized with K<sup>+</sup> respectively.</p> Full article ">Figure 20
<p>MALDI-TOF mass spectrum of PAIS prepared under magnetic stirring conditions (<span class="html-italic">C</span> = 2 M). Linear chains are represented by triangular symbols (▲) whereas cyclic species are characterized by circular symbols (●), both being cationized with Na<sup>+</sup>.</p> Full article ">Figure 21
<p>MALDI-TOF mass spectrum of PAIS prepared from the reaction of IS (<span class="html-italic">C</span> = 2.6 M) with CH2Cl2 added by drop by drop method and under high intensity mixing. Linear chains are represented by triangular symbols (▲) whereas cyclic species are characterized by circular symbols (●) both being cationized with Na<sup>+</sup>.</p> Full article ">Figure 22
<p>MALDI-TOF mass spectrum of PAIS prepared under high intensity mixing with IS (<span class="html-italic">C</span> = 2.6 M) and CH<sub>2</sub>Cl<sub>2</sub> in stoichiometric proportions. Linear chains cationized with Na<sup>+</sup> are represented by triangular symbols.</p> Full article ">
1090 KiB  
Article
Flammability of Cellulose-Based Fibers and the Effect of Structure of Phosphorus Compounds on Their Flame Retardancy
by Khalifah A. Salmeia, Milijana Jovic, Audrone Ragaisiene, Zaneta Rukuiziene, Rimvydas Milasius, Daiva Mikucioniene and Sabyasachi Gaan
Polymers 2016, 8(8), 293; https://doi.org/10.3390/polym8080293 - 10 Aug 2016
Cited by 68 | Viewed by 11048
Abstract
Cellulose fibers are promoted for use in various textile applications due their sustainable nature. Cellulose-based fibers vary considerably in their mechanical and flammability properties depending on their chemical composition. The chemical composition of a cellulose-based fiber is further dependent on their source (i.e., [...] Read more.
Cellulose fibers are promoted for use in various textile applications due their sustainable nature. Cellulose-based fibers vary considerably in their mechanical and flammability properties depending on their chemical composition. The chemical composition of a cellulose-based fiber is further dependent on their source (i.e., seed, leaf, cane, fruit, wood, bast, and grass). Being organic in nature, cellulose fibers, and their products thereof, pose considerable fire risk. In this work we have compared the flammability properties of cellulose fibers obtained from two different sources (i.e., cotton and peat). Compared to cotton cellulose textiles, peat-based cellulose textiles burn longer with a prominent afterglow which can be attributed to the presence of lignin in its structure. A series of phosphoramidates were synthesized and applied on both cellulose textiles. From thermogravimetric and pyrolysis combustion flow analysis of the treated cellulose, we were able to relate the flame retardant efficacy of the synthesized phosphorus compounds to their chemical structure. The phosphoramidates with methyl phosphoester groups exhibited higher condensed phase flame retardant effects on both types of cellulose textiles investigated in this study. In addition, the bis-phosphoramidates exhibited higher flame retardant efficacy compared to the mono-phosphoramidates. Full article
(This article belongs to the Special Issue Recent Advances in Flame Retardancy of Textile Related Products)
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<p>TGA data of cellulose textiles.</p> Full article ">Scheme 1
<p>General structure of phosphoester derivatives.</p> Full article ">Scheme 2
<p>Interactions of phosphorus compounds with cellulose. Different colors.</p> Full article ">
0 pages, 4252 KiB  
Article
RETRACTED: A Bio Polymeric Adhesive Produced by Photo Cross-Linkable Technique
by Soliman Abdalla, Nabil Al-Aama and Maryam A. Al-Ghamdi
Polymers 2016, 8(8), 292; https://doi.org/10.3390/polym8080292 - 10 Aug 2016
Cited by 11 | Viewed by 7783 | Retraction
Abstract
The advantages of photo polymerization methods compared to thermal techniques are: rapid cure reactions, low energy demands, solvent free requirements and room temperature use. In order to form a macromer, polycaprolactone (PCL) was cross-linked via ultraviolet power with 2-isocyanatoethyl methacrylate. Different methods of [...] Read more.
The advantages of photo polymerization methods compared to thermal techniques are: rapid cure reactions, low energy demands, solvent free requirements and room temperature use. In order to form a macromer, polycaprolactone (PCL) was cross-linked via ultraviolet power with 2-isocyanatoethyl methacrylate. Different methods of characterization were carried out: estimation of swelling capacity, adhesive capacity (using aminated substrates), surface energy (by contact angle), and attenuated total reflectance Fourier transform infrared. In addition to these experiments, we carried out dynamical mechanical thermal analysis, thermogravimetry and thermorphology characterizations of PCL. Thus, it has been concluded that the prepared macromer could be transformed into membranes that were effective as a medical adhesive. The degree of cross linking has been estimated using two different techniques: swelling of the samples and photo cross linking of the samples with different periods of irradiation at relatively high UV-power (600 mW/cm2). Full article
(This article belongs to the Special Issue Renewable Polymeric Adhesives)
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Figure 1

Figure 1
<p>Before ultraviolet irradiation, the spectrum of attenuated total reflectance Fourier transform infrared spectroscopy due to poly carprolacton (PCL) adjusted with 2-isocyanatoethyl methacrylate in liquid phase.</p> Full article ">Figure 2
<p>Sequences of the different reactions which lead to the formation of the thin film: (<b>A</b>) Mixture of 2-isocyanatoethyl methacrylate (IEMA) and polycaprolactone (PCL); (<b>B</b>) The mixture IEMA and PCL after ultraviolet radiation.</p> Full article ">Figure 3
<p>After ultraviolet irradiation, attenuated total reflectance Fourier transform infrared spectroscopy due to the cross linked polycarprolacton (PCL) with 2-isocyanatoethyl methacrylate in liquid phase.</p> Full article ">Figure 4
<p>The applied force as a function of displacement at ambient temperature and pressure.</p> Full article ">Figure 5
<p>Two different magnifications of the formed-membrane illustrated by scanning electron microscope: (<b>A</b>) magnification 750×; and (<b>B</b>) magnification 3500×.</p> Full article ">Figure 6
<p>Measurement of the glass transition temperature using dynamic mechanical thermal analysis (DMTA) for poly carprolacton (PCL). Tangent delta is illustrated as a function of temperature in °C. Measurements were taken at 1, 5, 10 Hz.</p> Full article ">Figure 7
<p>Measurement of the glass transition temperature using dynamic mechanical thermal analysis (DMTA) for cross linked polycarprolacton (PCL) with 2-isocyanatoethyl methacrylate macrmer. Tangent delta is illustrated as a function of temperature in °C. Measurements were taken at 1, 5, 10 Hz.</p> Full article ">Figure 8
<p>The percentage of weight loss of cross linked polycarprolacton (PCL) with 2-isocyanatoethyl methacrylate macrmer as a function of temperature in °C. Red dots represent data after ultraviolet irradiation and black squares represent data before ultraviolet irradiation.</p> Full article ">Figure 9
<p>Biodegradation of cross linked polycaprolactone (PCL) with 2-isocyanatoethyl methacrylate macrmer within a period of incubation 6 weeks. Data are shown as mean ± SME (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 10
<p>Two different magnifications of the cross-linked samples illustrated by scanning electron microscope: (<b>A</b>) before 6 weeks incubation; and (<b>B</b>) after 6 weeks incubation.</p> Full article ">Figure 11
<p>The weight gain as a function of time.</p> Full article ">Figure 12
<p>Differential scanning calorimetric thermo-grams show the heat flow passing through PCL-2-isocyanatoethyl methacrylate (IEMA) samples as a function of temperature for different irradiation UV-doses.</p> Full article ">Figure 13
<p>Black-thick curve represents the cross linking degree through PCL-IEMA samples as a function of irradiation UV-doses in seconds. Red-thin curve shows the variation of melting point as a function of irradiation UV-doses in seconds.</p> Full article ">Figure 14
<p>Haemolytic index (HI) of the specimens with direct contact (not subjected to extraction); values HI of the specimens incubated in PBS and of the PBS extraction solution (indirect contact). Data are shown as mean ± SME (<span class="html-italic">n</span> = 3).</p> Full article ">
5580 KiB  
Article
Moisture Absorption/Desorption Effects on Flexural Property of Glass-Fiber-Reinforced Polyester Laminates: Three-Point Bending Test and Coupled Hygro-Mechanical Finite Element Analysis
by Xu Jiang, Jie Song, Xuhong Qiang, Henk Kolstein and Frans Bijlaard
Polymers 2016, 8(8), 290; https://doi.org/10.3390/polym8080290 - 10 Aug 2016
Cited by 33 | Viewed by 8868
Abstract
Influence of moisture absorption/desorption on the flexural properties of Glass-fibre-reinforced polymer (GFRP) laminates was experimentally investigated under hot/wet aging environments. To characterize mechanical degradation, three-point bending tests were performed following the ASTM test standard (ASTM D790-10A). The flexural properties of dry (0% M [...] Read more.
Influence of moisture absorption/desorption on the flexural properties of Glass-fibre-reinforced polymer (GFRP) laminates was experimentally investigated under hot/wet aging environments. To characterize mechanical degradation, three-point bending tests were performed following the ASTM test standard (ASTM D790-10A). The flexural properties of dry (0% Mt/M?), moisture unsaturated (30% Mt/M? and 50% Mt/M?) and moisture saturated (100% Mt/M?) specimens at both 20 and 40 °C test temperatures were compared. One cycle of moisture absorption-desorption process was considered in this study to investigate the mechanical degradation scale and the permanent damage of GFRP laminates induced by moisture diffusion. Experimental results confirm that the combination of moisture and temperature effects sincerely deteriorates the flexural properties of GFRP laminates, on both strength and stiffness. Furthermore, the reducing percentage of flexural strength is found much larger than that of E-modulus. Unrecoverable losses of E-modulus (15.0%) and flexural strength (16.4%) for the GFRP laminates experiencing one cycle of moisture absorption/desorption process are evident at the test temperature of 40 °C, but not for the case of 20 °C test temperature. Moreover, a coupled hygro-mechanical Finite Element (FE) model was developed to characterize the mechanical behaviors of GFRP laminates at different moisture absorption/desorption stages, and the modeling method was subsequently validated with flexural test results. Full article
(This article belongs to the Collection Fiber-Reinforced Polymer Composites in Structural Engineering)
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<p>Fibre-reinforced polymer (FRP) laminate specimen for flexural tests.</p> Full article ">Figure 2
<p>Climate chamber.</p> Full article ">Figure 3
<p>Flexural test device.</p> Full article ">Figure 4
<p>Termination rule of the flexural test. (<b>a</b>) Drop to 30% of the maximum load; (<b>b</b>) Maximum displacement of 10 mm.</p> Full article ">Figure 5
<p>Comparison of moisture uptake curve between test results and FE analysis on FRP specimens for flexural test.</p> Full article ">Figure 6
<p>Failure mode of the flexural test specimen.</p> Full article ">Figure 7
<p>Stress-strain curves of FRP specimens under flexural tests.</p> Full article ">Figure 8
<p>Environment-dependent flexural property degradation of FRP laminates. (<b>a</b>) E-modulus, 20 °C; (<b>b</b>) Strength, 20 °C; (<b>c</b>) E-modulus, 40 °C; (<b>d</b>) Strength, 40 °C.</p> Full article ">Figure 9
<p>FE model of the flexural test specimen.</p> Full article ">Figure 10
<p>Nominal moisture concentration distribution across the mid-plane of the FRP specimenwith 30% moisture uptake content (time = 24 h).</p> Full article ">Figure 11
<p>Nominal moisture concentration distribution across the mid-plane of the FRP specimen with 50% moisture uptake content (time = 229 h).</p> Full article ">Figure 12
<p>Comparison of experimental and FE results on the load-deflection curve of F-50%-20 °C specimens.</p> Full article ">Figure 13
<p>Comparison of experimental and FE results on the load-deflection curve of F-30%-40 °C-D specimens.</p> Full article ">
993 KiB  
Article
The Connection between Biaxial Orientation and Shear Thinning for Quasi-Ideal Rods
by Christian Lang, Joachim Kohlbrecher, Lionel Porcar and Minne Paul Lettinga
Polymers 2016, 8(8), 291; https://doi.org/10.3390/polym8080291 - 9 Aug 2016
Cited by 17 | Viewed by 6295
Abstract
The complete orientational ordering tensor of quasi-ideal colloidal rods is obtained as a function of shear rate by performing rheo-SANS (rheology with small angle neutron scattering) measurements on isotropic fd-virus suspensions in the two relevant scattering planes, the flow-gradient (1-2) and the flow-vorticity [...] Read more.
The complete orientational ordering tensor of quasi-ideal colloidal rods is obtained as a function of shear rate by performing rheo-SANS (rheology with small angle neutron scattering) measurements on isotropic fd-virus suspensions in the two relevant scattering planes, the flow-gradient (1-2) and the flow-vorticity (1-3) plane. Microscopic ordering can be identified as the origin of the observed shear thinning. A qualitative description of the rheological response by Smoluchowski, as well as Doi–Edwards–Kuzuu theory is possible, as we obtain a master curve for different concentrations, scaling the shear rate with the apparent collective rotational diffusion coefficient. However, the observation suggests that the interdependence of ordering and shear thinning at small shear rates is stronger than predicted. The extracted zero-shear viscosity matches the concentration dependence of the self-diffusion of rods in semi-dilute solutions, while the director tilts close towards the flow direction already at very low shear rates. In contrast, we observe a smaller dependence on the shear rate in the overall ordering at high shear rates, as well as an ever-increasing biaxiality. Full article
(This article belongs to the Special Issue Semiflexible Polymers)
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Full article ">Figure 1
<p>(<b>a</b>) Definition of angles in our scattering geometry as defined by the flow field, dashed lines are guides to the eye; (<b>b</b>) scattering planes visualized on behalf of the Couette cell, red circles indicate moving parts, red arrows show the direction of motion.</p> Full article ">Figure 2
<p>Porod plot for <math display="inline"> <semantics> <mrow> <mi>c</mi> <mo>=</mo> <mn>11</mn> </mrow> </semantics> </math> mg/mL without shear flow. The solid line is a <math display="inline"> <semantics> <msup> <mi>q</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </semantics> </math> fit and the dashed line a <math display="inline"> <semantics> <msup> <mi>q</mi> <mrow> <mo>-</mo> <mn>2</mn> </mrow> </msup> </semantics> </math> fit to the data. The <span class="html-italic">q</span>-ranges I and II of analysis are parted by the vertical lines. Inset: comparison of the azimuthal intensity profiles for <span class="html-italic">q</span>-ranges I and II.</p> Full article ">Figure 3
<p>Corrected viscosity versus the orientational order parameter <math display="inline"> <semantics> <mrow> <mo>〈</mo> <msub> <mi>P</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mi>ψ</mi> <mo>)</mo> </mrow> <mo>〉</mo> </mrow> </semantics> </math>. The full lines are calculated by Smoluchowski theory for the indicated concentrations, while the dashed line is based on Doi–Edwards–Kuzuu (DEK) theory for the smallest given concentration, and the dotted thick line is an empirical fit.</p> Full article ">Figure 4
<p>Zero-shear viscosity scaled by the solvent viscosity as a function of the volume fraction from data shifting. The dotted line is a least squares log-linear fit to the data points, while the other lines represent the different theories.</p> Full article ">Figure 5
<p>Shear alignment given by the orientational order parameter <math display="inline"> <semantics> <mrow> <mo>〈</mo> <msub> <mi>P</mi> <mn>2</mn> </msub> <mo>〉</mo> </mrow> </semantics> </math>, as well as shear thinning given by <math display="inline"> <semantics> <mrow> <msub> <mi>η</mi> <mtext>corr</mtext> </msub> <mo>:</mo> <mo>=</mo> <mi>η</mi> <mo>/</mo> <msub> <mi>η</mi> <mn>0</mn> </msub> </mrow> </semantics> </math> versus the effective Peclet number for the given concentrations. Theoretical curves are given as solid lines, and the dashed line is a least squares fit of the measurement.</p> Full article ">Figure 6
<p>Projected order parameter as a function of the (effective thickness-) corrected Peclet number for the measured concentrations; the numbers <span class="html-italic">j</span>–<span class="html-italic">k</span> indicate the unit vectors in the measurement plane.</p> Full article ">Figure 7
<p>(<b>a</b>) Measured largest eigenvalue of <span class="html-italic">S</span> as a function of the corrected Peclet number compared to the Smoluchowski theory, evaluated for two effective thickness values <math display="inline"> <semantics> <mrow> <msubsup> <mi>d</mi> <mrow> <mtext>eff</mtext> </mrow> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mn>3</mn> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <mn>8.6</mn> </mrow> </semantics> </math> (dotted line) and <math display="inline"> <semantics> <mrow> <msubsup> <mi>d</mi> <mrow> <mtext>eff</mtext> </mrow> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mn>2</mn> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <mn>12</mn> </mrow> </semantics> </math> (dashed line) at a concentration of 11 mg/mL. Inset: largest eigenvalue compared to Smoluchowski theory for two different rotational diffusion coefficients. Two regimes are marked, separated at <math display="inline"> <semantics> <mrow> <msub> <mi>τ</mi> <mi>r</mi> </msub> <mover accent="true"> <mi>γ</mi> <mo>˙</mo> </mover> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math>; (<b>b</b>) Measured azimuthal tilt angle <span class="html-italic">θ</span> [t] and largest projected order tensor eigenvalue <math display="inline"> <semantics> <mrow> <msub> <mi>λ</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>θ</mi> <mo>)</mo> </mrow> </mrow> </semantics> </math> [l] as a function of the corrected Peclet number, for two concentrations, compared to the Smoluchowski theory. The solid and dashed lines are theoretical curves for the two given concentrations; (<b>c</b>) Measured biaxiality parameter <span class="html-italic">T</span> (squares) versus corrected Peclet number compared to Smoluchowski theory for the two effective thicknesses <math display="inline"> <semantics> <mrow> <msubsup> <mi>d</mi> <mrow> <mtext>eff</mtext> </mrow> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mn>3</mn> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <mn>8.6</mn> </mrow> </semantics> </math> (solid line) and <math display="inline"> <semantics> <mrow> <msubsup> <mi>d</mi> <mrow> <mtext>eff</mtext> </mrow> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mn>2</mn> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <mn>12</mn> </mrow> </semantics> </math> (dashed line).</p> Full article ">
1972 KiB  
Article
Flame Retardant Polyamide Fibres: The Challenge of Minimising Flame Retardant Additive Contents with Added Nanoclays
by Richard Horrocks, Ahilan Sitpalan, Chen Zhou and Baljinder K. Kandola
Polymers 2016, 8(8), 288; https://doi.org/10.3390/polym8080288 - 9 Aug 2016
Cited by 41 | Viewed by 8355
Abstract
This work shows that halogen-free, flame retarded polyamide 6 (PA6), fabrics may be produced in which component fibres still have acceptable tensile properties and low levels (preferably ?10 wt %) of additives by incorporating a nanoclay along with two types of flame retardant [...] Read more.
This work shows that halogen-free, flame retarded polyamide 6 (PA6), fabrics may be produced in which component fibres still have acceptable tensile properties and low levels (preferably ?10 wt %) of additives by incorporating a nanoclay along with two types of flame retardant formulations. The latter include (i) aluminium diethyl phosphinate (AlPi) at 10 wt %, known to work principally in the vapour phase and (ii) ammonium sulphamate (AS)/dipentaerythritol (DP) system present at 2.5 and 1 wt % respectively, believed to be condense phase active. The nanoclay chosen is an organically modified montmorillonite clay, Cloisite 25A. The effect of each additive system is analysed in terms of its ability to maximise both filament tensile properties relative to 100% PA6 and flame retardant behaviour of knitted fabrics in a vertical orientation. None of the AlPi-containing formulations achieved self-extinguishability, although the presence of nanoclay promoted lower burning and melt dripping rates. The AS/DP-containing formulations with total flame retardant levels of 5.5 wt % or less showed far superior properties and with nanoclay, showed fabric extinction times ? 39 s and reduced melt dripping. The tensile and flammability results, supported by thermogravimetric analysis, have been interpreted in terms of the mechanism of action of each flame retardant/nanoclay type. Full article
(This article belongs to the Special Issue Recent Advances in Flame Retardancy of Textile Related Products)
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<p>Selected images of burning PA6 fabrics comprising AlPi and/or Cloisite 25A 40 s after extinction of the igniting flame.</p> Full article ">Figure 2
<p>Burning and extinguishing behaviour of ignited PA6/DP/AS/clay-based fabric samples: 10, 15, 20 and 25 s after extinction of the igniting flame.</p> Full article ">Figure 3
<p>PA6/AlPi/clay samples in (<b>a</b>) air and (<b>b</b>) nitrogen.</p> Full article ">Figure 4
<p>PA6/AS/DP/clay samples in (<b>a</b>) air and (<b>b</b>) nitrogen.</p> Full article ">Figure 5
<p>DTA responses in air of PA6a and PA6b control samples.</p> Full article ">
2043 KiB  
Article
Key Role of Reinforcing Structures in the Flame Retardant Performance of Self-Reinforced Polypropylene Composites
by Katalin Bocz, Dániel Simon, Tamás Bárány and György Marosi
Polymers 2016, 8(8), 289; https://doi.org/10.3390/polym8080289 - 8 Aug 2016
Cited by 14 | Viewed by 6245
Abstract
The flame retardant synergism between highly stretched polymer fibres and intumescent flame retardant systems was investigated in self-reinforced polypropylene composites. It was found that the structure of reinforcement, such as degree of molecular orientation, fibre alignment and weave type, has a particular effect [...] Read more.
The flame retardant synergism between highly stretched polymer fibres and intumescent flame retardant systems was investigated in self-reinforced polypropylene composites. It was found that the structure of reinforcement, such as degree of molecular orientation, fibre alignment and weave type, has a particular effect on the fire performance of the intumescent system. As little as 7.2 wt % additive content, one third of the amount needed in non-reinforced polypropylene matrix, was sufficient to reach a UL-94 V-0 rating. The best result was found in self-reinforced polypropylene composites reinforced with unidirectional fibres. In addition to the fire retardant performance, the mechanical properties were also evaluated. The maximum was found at optimal consolidation temperature, while the flame retardant additive in the matrix did not influence the mechanical performance up to the investigated 13 wt % concentration. Full article
(This article belongs to the Special Issue Recent Advances in Flame Retardancy of Textile Related Products)
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<p>Tensile strength and modulus of additive-free and flame retarded PP SRCs with UD, CP and PW reinforcement.</p> Full article ">Figure 2
<p>Heat release rate curves of non-reinforced and self-reinforced PP samples with flame retardant contents of 0 and 9 wt %.</p> Full article ">Figure 3
<p>Density of the UD SRCs prepared at different consolidation temperatures.</p> Full article ">Figure 4
<p>Peel strength of the UD SRCs prepared at different consolidation temperatures.</p> Full article ">Figure 5
<p>Tensile strength and modulus of the UD SRCs prepared at different consolidation temperatures.</p> Full article ">Figure 6
<p>Limiting oxygen index and UL-94 rating of the UD SRCs prepared at different consolidation temperatures.</p> Full article ">
8310 KiB  
Article
Novel Electrospun Polylactic Acid Nanocomposite Fiber Mats with Hybrid Graphene Oxide and Nanohydroxyapatite Reinforcements Having Enhanced Biocompatibility
by Chen Liu, Hoi Man Wong, Kelvin Wai Kwok Yeung and Sie Chin Tjong
Polymers 2016, 8(8), 287; https://doi.org/10.3390/polym8080287 - 8 Aug 2016
Cited by 101 | Viewed by 9850
Abstract
Graphene oxide (GO) and a nanohydroxyapatite rod (nHA) of good biocompatibility were incorporated into polylactic acid (PLA) through electrospinning to form nanocomposite fiber scaffolds for bone tissue engineering applications. The preparation, morphological, mechanical and thermal properties, as well as biocompatibility of electrospun PLA [...] Read more.
Graphene oxide (GO) and a nanohydroxyapatite rod (nHA) of good biocompatibility were incorporated into polylactic acid (PLA) through electrospinning to form nanocomposite fiber scaffolds for bone tissue engineering applications. The preparation, morphological, mechanical and thermal properties, as well as biocompatibility of electrospun PLA scaffolds reinforced with GO and/or nHA were investigated. Electron microscopic examination and image analysis showed that GO and nHA nanofillers refine the diameter of electrospun PLA fibers. Differential scanning calorimetric tests showed that nHA facilitates the crystallization process of PLA, thereby acting as a nucleating site for the PLA molecules. Tensile test results indicated that the tensile strength and elastic modulus of the electrospun PLA mat can be increased by adding 15 wt % nHA. The hybrid nanocomposite scaffold with 15 wt % nHA and 1 wt % GO fillers exhibited higher tensile strength amongst the specimens investigated. Furthermore, nHA and GO nanofillers enhanced the water uptake of PLA. Cell cultivation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alkaline phosphatase tests demonstrated that all of the nanocomposite scaffolds exhibit higher biocompatibility than the pure PLA mat, particularly for the scaffold with 15 wt % nHA and 1 wt % GO. Therefore, the novel electrospun PLA nanocomposite scaffold with 15 wt % nHA and 1 wt % GO possessing a high tensile strength and modulus, as well as excellent cell proliferation is a potential biomaterial for bone tissue engineering applications. Full article
(This article belongs to the Special Issue Biodegradable Polymers)
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Full article ">Figure 1
<p>Schematic illustration showing the preparation of electrospun nanocomposite fibrous mats. PLA, polylactic acid; GO, Graphene Oxide; nHA, nanohydroxyapatite rod; DCM, dichloromethane; DMF, <span class="html-italic">N</span>,<span class="html-italic">N</span>-dimethylformamide.</p> Full article ">Figure 2
<p>TEM image of nanohydroxyapatite rod (nHA).</p> Full article ">Figure 3
<p>(<b>a</b>) AFM image of GO with height profile across a scan line and (<b>b</b>) Raman spectra of GO and graphite.</p> Full article ">Figure 4
<p>SEM micrographs of electrospun (<b>a</b>) PLA; (<b>b</b>) PLA/15%nHA and (<b>c</b>) PLA/15%nHA-3%GO fibrous mats.</p> Full article ">Figure 5
<p>TEM micrograph of the PLA/15%nHA-3%GO nanocomposite fibrous mat. Fillers of PLA/15%nHA-3%GO fiber are indicated by an arrow.</p> Full article ">Figure 6
<p>FTIR spectra of (<b>a</b>) nHA; (<b>b</b>) GO and (<b>c</b>) pure PLA specimens.</p> Full article ">Figure 7
<p>FTIR spectra of (<b>a</b>) PLA/15%nHA; (<b>b</b>) PLA/15%nHA-1%GO; (<b>c</b>) PLA/15%nHA-2%GO and (<b>d</b>) PLA/15%nHA-3%GO nanocomposite fibers. The enlarged spectra in the wave number ranging from 500 to 700 cm<sup>−1</sup> are presented.</p> Full article ">Figure 8
<p>Second heating curves of electrospun (<b>a</b>) PLA; (<b>b</b>) PLA/15%nHA; (<b>c</b>) PLA/15%nHA-1%GO; (<b>d</b>) PLA/15%nHA-2%GO and (<b>e</b>) PLA/15%nHA-3%GO fibrous mats.</p> Full article ">Figure 9
<p>Tensile stress–strain curves of electrospun (<b>a</b>) PLA; (<b>b</b>) PLA/15%nHA; (<b>c</b>) PLA/15%nHA-1%GO; (<b>d</b>) PLA/15%nHA-2%GO and (<b>e</b>) PLA/15%nHA-3%GO fibrous mats.</p> Full article ">Figure 10
<p>Water absorption behavior of PLA and PLA-based composite nanofiber mats.</p> Full article ">Figure 11
<p>SEM images showing the attachment of osteoblasts on (<b>a</b>) PLA; (<b>b</b>) PLA/15%nHA and (<b>c</b>) PLA/15%nHA-2%GO fibrous mats.</p> Full article ">Figure 12
<p>The MTT assay results of Saos-2 cells cultured on neat PLA and its composite fibrous mats for 3, 7 and 10 days. * <span class="html-italic">p</span> &lt; 0.05.</p> Full article ">Figure 13
<p>ALP activity of Saos-2 cells cultured on neat PLA and its composite fibrous mats for 3, 7 and 14 days. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01.</p> Full article ">
8244 KiB  
Review
Semiflexible Chains at Surfaces: Worm-Like Chains and beyond
by Jörg Baschnagel, Hendrik Meyer, Joachim Wittmer, Igor Kulić, Hervé Mohrbach, Falko Ziebert, Gi-Moon Nam, Nam-Kyung Lee and Albert Johner
Polymers 2016, 8(8), 286; https://doi.org/10.3390/polym8080286 - 8 Aug 2016
Cited by 39 | Viewed by 9976
Abstract
We give an extended review of recent numerical and analytical studies on semiflexible chains near surfaces undertaken at Institut Charles Sadron (sometimes in collaboration) with a focus on static properties. The statistical physics of thin confined layers, strict two-dimensional (2D) layers and adsorption [...] Read more.
We give an extended review of recent numerical and analytical studies on semiflexible chains near surfaces undertaken at Institut Charles Sadron (sometimes in collaboration) with a focus on static properties. The statistical physics of thin confined layers, strict two-dimensional (2D) layers and adsorption layers (both at equilibrium with the dilute bath and from irreversible chemisorption) are discussed for the well-known worm-like-chain (WLC) model. There is mounting evidence that biofilaments (except stable d-DNA) are not fully described by the WLC model. A number of augmented models, like the (super) helical WLC model, the polymorphic model of microtubules (MT) and a model with (strongly) nonlinear flexural elasticity are presented, and some aspects of their surface behavior are analyzed. In many cases, we use approaches different from those in our previous work, give additional results and try to adopt a more general point of view with the hope to shed some light on this complex field. Full article
(This article belongs to the Special Issue Semiflexible Polymers)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Stiffness effects and lattice artifacts for bond-fluctuation model (BFM) data obtained for <math display="inline"> <semantics> <mrow> <mi>M</mi> <mo>=</mo> <mn>200</mn> </mrow> </semantics> </math> chains of length <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>20</mn> </mrow> </semantics> </math> at a volume fraction <math display="inline"> <semantics> <mrow> <mi>ϕ</mi> <mo>=</mo> <mn>8</mn> <mi>N</mi> <mi>M</mi> <mo>/</mo> <mi>V</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> </mrow> </semantics> </math> of occupied lattice sites at a temperature <math display="inline"> <semantics> <mrow> <mi>T</mi> <mo>=</mo> <mn>1</mn> <mo>/</mo> <mi>β</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math> [<a href="#B41-polymers-08-00286" class="html-bibr">41</a>]. Panel (<b>a</b>) shows the effective bond length <math display="inline"> <semantics> <mrow> <msub> <mi>b</mi> <mtext>e</mtext> </msub> <mo>=</mo> <msub> <mi>R</mi> <mtext>e</mtext> </msub> <mrow> <mo>(</mo> <mi>N</mi> <mo>)</mo> </mrow> <mo>/</mo> <msup> <mrow> <mo>(</mo> <mi>N</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> <mrow> <mn>1</mn> <mo>/</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics> </math>, obtained from the root-mean-squared chain end-to-end distance <math display="inline"> <semantics> <mrow> <msub> <mi>R</mi> <mtext>e</mtext> </msub> <mrow> <mo>(</mo> <mi>N</mi> <mo>)</mo> </mrow> </mrow> </semantics> </math> and the (rescaled) center-of-mass self-diffusion coefficient <math display="inline"> <semantics> <msub> <mi>D</mi> <mi>cm</mi> </msub> </semantics> </math> as a function of the dimensionless parameter <math display="inline"> <semantics> <mrow> <mi>x</mi> <mo>=</mo> <mi>β</mi> <mi>ϵ</mi> </mrow> </semantics> </math>. A snapshot of a configuration at <math display="inline"> <semantics> <mrow> <mi>ϵ</mi> <mo>=</mo> <mn>10</mn> </mrow> </semantics> </math> is given in Panel (<b>b</b>). The chains are seen to align along the three principal lattice axes.</p> Full article ">Figure 2
<p>Snapshots of semiflexible 2D polymers of length <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>256</mn> </mrow> </semantics> </math> obtained by means of molecular dynamics simulation of a Kremer–Grest bead-spring model [<a href="#B56-polymers-08-00286" class="html-bibr">56</a>,<a href="#B79-polymers-08-00286" class="html-bibr">79</a>]. We show data for four concentrations <math display="inline"> <semantics> <mrow> <mi>c</mi> <mo>=</mo> <mi>N</mi> <mi>M</mi> <mo>/</mo> <msup> <mi>L</mi> <mn>2</mn> </msup> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>125</mn> </mrow> </semantics> </math> (<math display="inline"> <semantics> <mrow> <mi>M</mi> <mo>=</mo> <mn>192</mn> </mrow> </semantics> </math> chains, linear box size <math display="inline"> <semantics> <mrow> <mi>L</mi> <mo>≈</mo> <mn>627</mn> </mrow> </semantics> </math>), <math display="inline"> <semantics> <mrow> <mi>c</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>250</mn> </mrow> </semantics> </math> (<math display="inline"> <semantics> <mrow> <mi>M</mi> <mo>=</mo> <mn>192</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>L</mi> <mo>≈</mo> <mn>443</mn> </mrow> </semantics> </math>), <math display="inline"> <semantics> <mrow> <mi>c</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>500</mn> </mrow> </semantics> </math> (<math display="inline"> <semantics> <mrow> <mi>M</mi> <mo>=</mo> <mn>192</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>L</mi> <mo>≈</mo> <mn>313</mn> </mrow> </semantics> </math>) and <math display="inline"> <semantics> <mrow> <mi>c</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>750</mn> </mrow> </semantics> </math> (<math display="inline"> <semantics> <mrow> <mi>M</mi> <mo>=</mo> <mn>384</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>L</mi> <mo>≈</mo> <mn>362</mn> </mrow> </semantics> </math>) and five bending penalties <math display="inline"> <semantics> <mrow> <mi>ϵ</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math>, 2, 4, 8 and 16 (from the bottom to the top). Only small subvolumes of much larger boxes are represented. The configurations have been sampled by increasing <span class="html-italic">ϵ</span> starting with flexible and compact chain systems (<math display="inline"> <semantics> <mrow> <mi>ϵ</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math>) [<a href="#B68-polymers-08-00286" class="html-bibr">68</a>,<a href="#B76-polymers-08-00286" class="html-bibr">76</a>,<a href="#B80-polymers-08-00286" class="html-bibr">80</a>]. While the chains remain compact and segregated at low densities and stiffnesses below the dashed line, they are seen in the opposite limit to align (at least) locally, forming bundles of chains with hairpins, which are extremely difficult to equilibrate.</p> Full article ">Figure 3
<p>Rescaled sub-chain size <math display="inline"> <semantics> <mrow> <mi>y</mi> <mo>=</mo> <msubsup> <mi>R</mi> <mtext>e</mtext> <mn>2</mn> </msubsup> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>/</mo> <mrow> <mo>(</mo> <mi>s</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </semantics> </math> with <span class="html-italic">s</span> being the arc-length (sub-chain length) for four concentrations and three stiffness penalties corresponding to systems below and around the dashed line in <a href="#polymers-08-00286-f002" class="html-fig">Figure 2</a>. The symbols refer to flexible systems (<math display="inline"> <semantics> <mrow> <mi>ϵ</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math>); the line width for <math display="inline"> <semantics> <mrow> <mi>ϵ</mi> <mo>=</mo> <mn>2</mn> </mrow> </semantics> </math> and 4 increases with density. The dash-dotted line corresponds to the asymptotic slope for perfectly rigid chains. Note that <math display="inline"> <semantics> <mrow> <mi>y</mi> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </semantics> </math> becomes strongly non-monotonous with increasing <span class="html-italic">ϵ</span>. However, for a given density and <math display="inline"> <semantics> <mrow> <mi>s</mi> <mo>→</mo> <mi>N</mi> </mrow> </semantics> </math>, all <math display="inline"> <semantics> <mrow> <mi>y</mi> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </semantics> </math> become similar as long as the system remains isotropic, i.e., <span class="html-italic">ϵ</span> is not too large. Independent of the rigidity, the overall chain size is thus ruled by the (persistence length independent) distance <math display="inline"> <semantics> <mrow> <msub> <mi>d</mi> <mtext>cm</mtext> </msub> <mo>≈</mo> <msup> <mrow> <mo>(</mo> <mi>N</mi> <mo>/</mo> <mi>c</mi> <mo>)</mo> </mrow> <mrow> <mn>1</mn> <mo>/</mo> <mi>D</mi> </mrow> </msup> </mrow> </semantics> </math> between chains.</p> Full article ">Figure 4
<p>Log-log plot of the tangent/tangent correlation function <math display="inline"> <semantics> <mrow> <mi>C</mi> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>=</mo> <mo>〈</mo> <mi>cos</mi> <mi>θ</mi> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>〉</mo> </mrow> </semantics> </math> versus arc-length <span class="html-italic">s</span> for a 3D polymer melt with chains of length <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>1024</mn> </mrow> </semantics> </math>. The symbols show data from MD simulations for a Kremer–Grest-like bead-spring model [<a href="#B10-polymers-08-00286" class="html-bibr">10</a>] with three bending penalties: <math display="inline"> <semantics> <mrow> <mi>ϵ</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo>,</mo> <mn>2</mn> </mrow> </semantics> </math>. The model is similar to the one shown in <a href="#polymers-08-00286-f002" class="html-fig">Figure 2</a>. Thus, the melt with <math display="inline"> <semantics> <mrow> <mi>ϵ</mi> <mo>≤</mo> <mn>2</mn> </mrow> </semantics> </math> is isotropic, the value <math display="inline"> <semantics> <mrow> <mi>ϵ</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math> corresponding to fully-flexible chains. The abscissa is scaled by the persistence length <span class="html-italic">ℓ</span> obtained from a fit of the initial decay of <math display="inline"> <semantics> <mrow> <mi>C</mi> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </semantics> </math> to Equation (<a href="#FD1-polymers-08-00286" class="html-disp-formula">1</a>); see the dashed line in the figure. The solid lines indicate the power law, <math display="inline"> <semantics> <mrow> <mi>C</mi> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>∼</mo> <msup> <mi>s</mi> <mrow> <mo>-</mo> <mn>3</mn> <mo>/</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics> </math>, expected from corrections to chain ideality [<a href="#B10-polymers-08-00286" class="html-bibr">10</a>,<a href="#B11-polymers-08-00286" class="html-bibr">11</a>].</p> Full article ">Figure 5
<p>Loop distribution as simulated by molecular dynamics for two chain lengths (<math display="inline"> <semantics> <mrow> <mi>S</mi> <mo>=</mo> <mn>30</mn> </mrow> </semantics> </math> b and <math display="inline"> <semantics> <mrow> <mi>S</mi> <mo>=</mo> <mn>250</mn> </mrow> </semantics> </math> b). The persistence length is <math display="inline"> <semantics> <mrow> <mi>ℓ</mi> <mo>=</mo> <mn>10</mn> <mo>.</mo> <mn>1</mn> </mrow> </semantics> </math> b throughout. (left) Distribution of the internal loop size upon first adsorption of a loop of size <span class="html-italic">S</span>; only the smallest of the generated internal loops is taken into account; the full distribution is symmetric about <math display="inline"> <semantics> <mrow> <mi>S</mi> <mo>/</mo> <mn>2</mn> </mrow> </semantics> </math>. We show the power law fit by the single loop partition function (dashed lines) for the stiff loop and for the flexible loop, which apply where they should. Note the rather narrow crossover around <math display="inline"> <semantics> <mrow> <mi>s</mi> <mo>=</mo> <mn>2</mn> <mi>ℓ</mi> </mrow> </semantics> </math>. The product of loop flexible partition functions nicely accounts for the flattening near <math display="inline"> <semantics> <mrow> <mi>s</mi> <mo>=</mo> <mi>S</mi> <mo>/</mo> <mn>2</mn> </mrow> </semantics> </math> required by symmetry. (right) Distribution of the size of the loop generated by first re-adsorption of a tail of length <math display="inline"> <semantics> <mrow> <mi>S</mi> <mo>/</mo> <mn>2</mn> </mrow> </semantics> </math>. Again, the single loop partition functions fit where they should; the narrow crossover is now located around <math display="inline"> <semantics> <mrow> <mi>s</mi> <mo>=</mo> <mi>ℓ</mi> </mrow> </semantics> </math>. The product of the flexible loop and tail partition functions accounts for the upturn near <math display="inline"> <semantics> <mrow> <mi>s</mi> <mo>=</mo> <mn>125</mn> </mrow> </semantics> </math> b where the small tail partition function dominates.</p> Full article ">Figure 6
<p>(<b>a</b>) Schematic squeelix with the angle <span class="html-italic">ϕ</span> that is slaved to the twist angle <span class="html-italic">ψ</span> given by the line in black; (<b>b</b>) typical shape of a squeelix for <math display="inline"> <semantics> <mrow> <mi>γ</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math> (see Equation (<a href="#FD19-polymers-08-00286" class="html-disp-formula">19</a>)) with a single twist-kink; (<b>c</b>) a squeelix in the dilute regime of twist-kinks with <math display="inline"> <semantics> <mrow> <mi>γ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>997</mn> </mrow> </semantics> </math>; (<b>d</b>) a squeelix in the dense regime of twist-kinks with <math display="inline"> <semantics> <mrow> <mi>γ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>52</mn> </mrow> </semantics> </math>. The ground states (b), (c) and (d) are from [<a href="#B121-polymers-08-00286" class="html-bibr">121</a>].</p> Full article ">Figure 7
<p><math display="inline"> <semantics> <mrow> <mi>P</mi> <mo>(</mo> <mi>θ</mi> <mo>)</mo> </mrow> </semantics> </math> for <math display="inline"> <semantics> <mrow> <mi>S</mi> <mo>=</mo> <mn>100</mn> <mi>b</mi> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>ω</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>01</mn> <mo>/</mo> <mi>b</mi> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>ℓ</mi> <mo>=</mo> <mn>1000</mn> <mi>b</mi> </mrow> </semantics> </math> obtained by convolution according to Equation (<a href="#FD23-polymers-08-00286" class="html-disp-formula">23</a>) using Equation (<a href="#FD22-polymers-08-00286" class="html-disp-formula">22</a>). The Boltzmann weight of a twist kink is <math display="inline"> <semantics> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>E</mi> </mrow> </msup> </semantics> </math>. The lines correspond to <math display="inline"> <semantics> <mrow> <mi>E</mi> <mo>=</mo> </mrow> </semantics> </math> 4 (green), 6 (blue) and 8 (black). The thick dashed line corresponds to <math display="inline"> <semantics> <mrow> <mi>E</mi> <mo>=</mo> <mo>-</mo> <mi>l</mi> <mi>o</mi> <mi>g</mi> <mo>(</mo> <mi>b</mi> <mi>ω</mi> <mo>)</mo> <mo>≈</mo> <mn>4</mn> <mo>.</mo> <mn>6</mn> </mrow> </semantics> </math>.</p> Full article ">Figure 8
<p><math display="inline"> <semantics> <mrow> <msubsup> <mi>R</mi> <mi>g</mi> <mn>2</mn> </msubsup> <mrow> <mo>(</mo> <mi>S</mi> <mo>)</mo> </mrow> </mrow> </semantics> </math> for <math display="inline"> <semantics> <mrow> <mi>ω</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>01</mn> <mo>/</mo> <mi>b</mi> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <msub> <mi>l</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>1000</mn> <mi>b</mi> </mrow> </semantics> </math>. The Boltzmann weight of a twist kink is <math display="inline"> <semantics> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>E</mi> </mrow> </msup> </semantics> </math>. The thin lines are for <math display="inline"> <semantics> <mrow> <mi>E</mi> <mo>=</mo> <mn>2</mn> <mo>,</mo> <mn>4</mn> <mo>,</mo> <mn>6</mn> <mo>,</mo> <mn>8</mn> </mrow> </semantics> </math> and 10 from top to bottom. The thick line indicate <math display="inline"> <semantics> <msubsup> <mi>R</mi> <mi>g</mi> <mn>2</mn> </msubsup> </semantics> </math> with <math display="inline"> <semantics> <mrow> <mi>E</mi> <mo>=</mo> <mo>-</mo> <mi>l</mi> <mi>o</mi> <mi>g</mi> <mo>(</mo> <mi>b</mi> <mi>ω</mi> <mo>)</mo> <mo>≈</mo> <mn>4</mn> <mo>.</mo> <mn>6</mn> </mrow> </semantics> </math>. Undulations appear for <math display="inline"> <semantics> <mrow> <mi>E</mi> <mo>&gt;</mo> <mo>-</mo> <mi>l</mi> <mi>o</mi> <mi>g</mi> <mo>(</mo> <mi>b</mi> <mi>ω</mi> <mo>)</mo> </mrow> </semantics> </math>.</p> Full article ">Figure 9
<p>(<b>a</b>) Free energy landscapes without applied force (<math display="inline"> <semantics> <mrow> <mi>f</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math>) and (<b>b, c</b>) under increasing force (<math display="inline"> <semantics> <mrow> <mi>f</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>25</mn> <msub> <mi>k</mi> <mi>B</mi> </msub> <mi>T</mi> <mo>/</mo> <mi>b</mi> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>f</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>50</mn> <msub> <mi>k</mi> <mi>B</mi> </msub> <mi>T</mi> <mo>/</mo> <mi>b</mi> </mrow> </semantics> </math>). To fix the force scale: for <math display="inline"> <semantics> <mrow> <mi>b</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> </mrow> </semantics> </math> nm, given <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mi>B</mi> </msub> <mi>T</mi> <mo>≈</mo> <mn>4</mn> </mrow> </semantics> </math> pNnm, <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mi>B</mi> </msub> <mi>T</mi> <mo>/</mo> <mi>b</mi> <mo>≈</mo> <mn>8</mn> </mrow> </semantics> </math> pN.</p> Full article ">Figure 10
<p>(<b>a</b>) Two filaments are coupled with elastic springs forming a simple two-chain bundle; (<b>b</b>) the shear and bending degrees of freedom become strongly coupled, leading to long-range deformation effects. An arc formed in the region of length <span class="html-italic">l</span> (blue line) around the origin induces two counter-arcs with opposite curvature in its next proximity. The deformations are screened and vanish only at length scales longer than the elastic screening length <span class="html-italic">λ</span>.</p> Full article ">Figure 11
<p>A semiflexible filament with elastic tails that cross-link points along its backbone becomes bistable. If the cross-linking point intervals overlap in addition (red and black chains), the curvature switching becomes cooperative. The single arc state in the middle is the energetically most stable (indicated by bold and dashed arrows).</p> Full article ">Figure 12
<p>Polymorphic crunching: (<b>a</b>) Nonlinear bendable units are coupled in-plane of bending by a ring closure constraint (<b>b</b>). The constraint modifies their effective free energy and gives rise to a bistable monomer potential. (<b>c</b>) Two out of exponentially many energetically-equivalent ground state realizations. Blue and light-blue indicate the regions of opposite curvature.</p> Full article ">Figure 13
<p>The polymorphic model of microtubules. (<b>a</b>) The switchability of tubulin dimers leads to a competition of three states of the microtubule’s cross-section: straight and long (L), curved (C) and straight and short (S). (<b>b</b>) “Phase diagram” of the polymorphic microtubule model as a function of generalized force <span class="html-italic">f</span> vs. torque <span class="html-italic">m</span>. The existing states in the respective regions are ordered by their polymorphic energies, the one at the bottom having minimum energy. (<b>c</b>) An intermittent buckling event, for a microtubule transported along a motor-covered surface, in case of <math display="inline"> <semantics> <mrow> <mi>f</mi> <mo>≃</mo> <mn>0</mn> <mo>.</mo> <mn>7</mn> </mrow> </semantics> </math> (corresponding to small switching energies <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mi>G</mi> <mo>≃</mo> <mn>0</mn> </mrow> </semantics> </math>). The behavior observed is the one of a regular WLC chain. (<b>d</b>) An intermittent buckling event in case of <math display="inline"> <semantics> <mrow> <mi>f</mi> <mo>≃</mo> <mn>0</mn> <mo>.</mo> <mn>4</mn> </mrow> </semantics> </math> (corresponding <math display="inline"> <semantics> <mrow> <mo>Δ</mo> <mi>G</mi> <mo>≃</mo> <mn>5</mn> <mspace width="0.166667em"/> <mrow> <msub> <mi mathvariant="normal">k</mi> <mi mathvariant="normal">B</mi> </msub> <mi mathvariant="normal">T</mi> </mrow> <mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math>. The microtubule curls up.</p> Full article ">
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Article
Enhancing the Adhesive Strength of a Plywood Adhesive Developed from Hydrolyzed Specified Risk Materials
by Birendra B. Adhikari, Pooran Appadu, Vadim Kislitsin, Michael Chae, Phillip Choi and David C. Bressler
Polymers 2016, 8(8), 285; https://doi.org/10.3390/polym8080285 - 8 Aug 2016
Cited by 34 | Viewed by 8554
Abstract
The current production of wood composites relies mostly on formaldehyde-based adhesives such as urea formaldehyde (UF) and phenol formaldehyde (PF) resins. As these resins are produced from non-renewable resources, and there are some ongoing issues with possible health hazard due to formaldehyde emission [...] Read more.
The current production of wood composites relies mostly on formaldehyde-based adhesives such as urea formaldehyde (UF) and phenol formaldehyde (PF) resins. As these resins are produced from non-renewable resources, and there are some ongoing issues with possible health hazard due to formaldehyde emission from such products, the purpose of this research was to develop a formaldehyde-free plywood adhesive utilizing waste protein as a renewable feedstock. The feedstock for this work was specified risk material (SRM), which is currently being disposed of either by incineration or by landfilling. In this report, we describe a technology for utilization of SRM for the development of an environmentally friendly plywood adhesive. SRM was thermally hydrolyzed using a Canadian government-approved protocol, and the peptides were recovered from the hydrolyzate. The recovered peptides were chemically crosslinked with polyamidoamine-epichlorohydrin (PAE) resin to develop an adhesive system for bonding of plywood specimens. The effects of crosslinking time, peptides/crosslinking agent ratio, and temperature of hot pressing of plywood specimens on the strength of formulated adhesives were investigated. Formulations containing as much as 78% (wt/wt) peptides met the ASTM (American Society for Testing and Materials) specifications of minimum dry and soaked shear strength requirement for UF resin type adhesives. Under the optimum conditions tested, the peptides–PAE resin-based formulations resulted in plywood specimens having comparable dry as well as soaked shear strength to that of commercial PF resin. Full article
(This article belongs to the Special Issue Renewable Polymeric Adhesives)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Chemical structure of PAE resin (<b>a</b>); and plausible chemical reactions occurring during chemical crosslinking of PAE resin with peptides (<b>b</b>). Reactions (1) and (2) represent self-crosslinking reactions of PAE molecules, which occur due to the reactions of the azetidinium groups with secondary amines (Reaction (1)) as well as terminal carboxylate groups (Reaction (2)) of PAE producing a homocrosslinked polymer [<a href="#B12-polymers-08-00285" class="html-bibr">12</a>,<a href="#B20-polymers-08-00285" class="html-bibr">20</a>,<a href="#B21-polymers-08-00285" class="html-bibr">21</a>,<a href="#B22-polymers-08-00285" class="html-bibr">22</a>,<a href="#B23-polymers-08-00285" class="html-bibr">23</a>]. Co-crosslinking of PAE resin and peptides occurs due to the reactions of azetidinium groups of the resin with amine (Reaction (3)) and carboxylate (Reaction (4)) groups of the peptides [<a href="#B12-polymers-08-00285" class="html-bibr">12</a>,<a href="#B20-polymers-08-00285" class="html-bibr">20</a>].</p> Full article ">Figure 2
<p>Lap shear strength of plywood specimens bonded with peptides or PAE resin alone (<b>a</b>); or peptides–PAE adhesives crosslinked for various amounts of time (<b>b</b>). For peptides–PAE formulations, 1.88 g of peptides were mixed with 20.0 g PAE resin (peptides: PAE resin = 1:1.33 on dry weight basis). Specimens were hot pressed at 120 °C and 3.5 Mpa for five min. Error bars indicate standard deviation of six plywood specimen measurements. Some specimens delaminated when soaked in water (DL). Means that do not share a letter are significantly different (Tukey, 95% confidence level). The minimum shear strength requirements as specified by ASTM D4690 are shown: 2.344 MPa for dry shear strength; and 1.93 MPa for soaked shear strength [<a href="#B34-polymers-08-00285" class="html-bibr">34</a>].</p> Full article ">Figure 3
<p>Effect of the weight ratio of peptides and PAE on lap shear strength of plywood specimens bonded with the peptides–PAE adhesive. Specimens were crosslinked for 120 min, and then hot pressed at 120 °C and 3.5 MPa for five min. Error bars are standard deviation of six plywood specimen measurements. Specimens that delaminated when soaked in water are indicated (DL). Means that do not share a letter are significantly different (Tukey, 95% confidence level). The minimum shear strength requirements as specified by ASTM D4690 are shown: 2.344 MPa for dry shear strength; 1.93 MPa for soaked shear strength [<a href="#B34-polymers-08-00285" class="html-bibr">34</a>].</p> Full article ">Figure 4
<p>Effect of hot press temperature on lap shear strength of plywood specimens bonded with the peptides–PAE adhesive. For these experiments, a formulation consisting of 46% PAE resin and 54% peptides was used after crosslinking for 120 min. Specimens were hot pressed at 3.5 MPa for five min. Error bars are standard deviation of six plywood specimen measurements. Means that do not share a letter are significantly different (Tukey, 95% confidence level). The minimum shear strength requirements as specified by ASTM D4690 are indicated.</p> Full article ">Figure 5
<p>Comparison of adhesive performance of peptides–PAE resin to that of a commercially-available phenol–formaldehyde (PF) resin. Specimens were hot pressed at 3.5 MPa for five min at hot pressing temperature shown in parenthesis. Error bars are standard deviation of six plywood specimen measurements. Means that do not share a letter are significantly different (Tukey, 95% confidence level). The minimum shear strength requirements as specified by ASTM D4690 are indicated.</p> Full article ">
2157 KiB  
Article
Finsler Geometry Modeling of Phase Separation in Multi-Component Membranes
by Satoshi Usui and Hiroshi Koibuchi
Polymers 2016, 8(8), 284; https://doi.org/10.3390/polym8080284 - 4 Aug 2016
Cited by 7 | Viewed by 5447
Abstract
A Finsler geometric surface model is studied as a coarse-grained model for membranes of three components, such as zwitterionic phospholipid (DOPC), lipid (DPPC) and an organic molecule (cholesterol). To understand the phase separation of liquid-ordered (DPPC rich) L o and liquid-disordered (DOPC rich) [...] Read more.
A Finsler geometric surface model is studied as a coarse-grained model for membranes of three components, such as zwitterionic phospholipid (DOPC), lipid (DPPC) and an organic molecule (cholesterol). To understand the phase separation of liquid-ordered (DPPC rich) L o and liquid-disordered (DOPC rich) L d , we introduce a binary variable ? ( = ± 1 ) into the triangulated surface model. We numerically determine that two circular and stripe domains appear on the surface. The dependence of the morphological change on the area fraction of L o is consistent with existing experimental results. This provides us with a clear understanding of the origin of the line tension energy, which has been used to understand these morphological changes in three-component membranes. In addition to these two circular and stripe domains, a raft-like domain and budding domain are also observed, and the several corresponding phase diagrams are obtained. Full article
(This article belongs to the Special Issue Semiflexible Polymers)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The dependence of <math display="inline"> <semantics> <msub> <mi>κ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> </semantics> </math> and <math display="inline"> <semantics> <msub> <mi>γ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> </semantics> </math> on four possible combinations of <math display="inline"> <semantics> <msub> <mi>L</mi> <mi>o</mi> </msub> </semantics> </math> and <math display="inline"> <semantics> <msub> <mi>L</mi> <mi>d</mi> </msub> </semantics> </math>: (<b>a</b>) <math display="inline"> <semantics> <mrow> <msub> <mi>κ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>γ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <mrow> <mo>(</mo> <mi>c</mi> <mo>+</mo> <msup> <mi>c</mi> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> <mo>)</mo> </mrow> <mo>/</mo> <mn>2</mn> </mrow> </semantics> </math> on <math display="inline"> <semantics> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mi>o</mi> </msub> <mo>,</mo> <msub> <mi>L</mi> <mi>o</mi> </msub> <mo>)</mo> </mrow> </semantics> </math>; (<b>b</b>) <math display="inline"> <semantics> <mrow> <msub> <mi>κ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>γ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>+</mo> <mi>c</mi> <mo>+</mo> <msup> <mi>c</mi> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> <mo>)</mo> </mrow> <mo>/</mo> <mn>4</mn> </mrow> </semantics> </math> on <math display="inline"> <semantics> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mi>o</mi> </msub> <mo>,</mo> <msub> <mi>L</mi> <mi>d</mi> </msub> <mo>)</mo> </mrow> </semantics> </math>; and (<b>c</b>) <math display="inline"> <semantics> <mrow> <msub> <mi>κ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>γ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math> on <math display="inline"> <semantics> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mi>d</mi> </msub> <mo>,</mo> <msub> <mi>L</mi> <mi>d</mi> </msub> <mo>)</mo> </mrow> </semantics> </math>. <math display="inline"> <semantics> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mrow> <mi>o</mi> <mo>,</mo> <mi>d</mi> </mrow> </msub> <mo>,</mo> <msub> <mi>L</mi> <mrow> <mi>o</mi> <mo>,</mo> <mi>d</mi> </mrow> </msub> <mo>)</mo> </mrow> </semantics> </math> correspond to the bonds represented by the duplicated lines.</p> Full article ">Figure 2
<p>Three different values of <math display="inline"> <semantics> <msub> <mi>γ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> </semantics> </math> and <math display="inline"> <semantics> <msub> <mi>κ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> </semantics> </math> vs. <span class="html-italic">c</span>, where <math display="inline"> <semantics> <mrow> <msub> <mi>κ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>γ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <mrow> <mo>(</mo> <mi>c</mi> <mo>+</mo> <msup> <mi>c</mi> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> <mo>)</mo> </mrow> <mo>/</mo> <mn>2</mn> </mrow> </semantics> </math> on the <math display="inline"> <semantics> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mi>o</mi> </msub> <mo>,</mo> <msub> <mi>L</mi> <mi>o</mi> </msub> <mo>)</mo> </mrow> </semantics> </math> boundary, <math display="inline"> <semantics> <mrow> <msub> <mi>κ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>γ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>+</mo> <mi>c</mi> <mo>+</mo> <msup> <mi>c</mi> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> <mo>)</mo> </mrow> <mo>/</mo> <mn>4</mn> </mrow> </semantics> </math> on the <math display="inline"> <semantics> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mi>o</mi> </msub> <mo>,</mo> <msub> <mi>L</mi> <mi>d</mi> </msub> <mo>)</mo> </mrow> </semantics> </math> boundary and <math display="inline"> <semantics> <mrow> <msub> <mi>κ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>γ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math> on the <math display="inline"> <semantics> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mi>d</mi> </msub> <mo>,</mo> <msub> <mi>L</mi> <mi>d</mi> </msub> <mo>)</mo> </mrow> </semantics> </math> boundary. The dashed lines denote the values of <span class="html-italic">c</span> assumed in some of the simulations.</p> Full article ">Figure 3
<p>A phase diagram of Model 1 on the <math display="inline"> <semantics> <mrow> <mi>λ</mi> <mo>−</mo> <msub> <mi>ϕ</mi> <mi>o</mi> </msub> </mrow> </semantics> </math> plane at <math display="inline"> <semantics> <mrow> <mi>κ</mi> <mo>=</mo> <mn>7</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>c</mi> <mo>=</mo> <mn>5</mn> </mrow> </semantics> </math> and the snapshots of surfaces obtained at the points indicated by the symbol (<math display="inline"> <semantics> <mrow> <mo mathcolor="red">×</mo> </mrow> </semantics> </math>). The solid lines denote the phase boundaries, and the dashed lines denote the positions for the simulations for <a href="#polymers-08-00284-f004" class="html-fig">Figure 4</a>a–c. The solid circles (<math display="inline"> <semantics> <mrow> <mi mathcolor="red">•</mi> </mrow> </semantics> </math>) denote the data points of the simulations for the phase boundaries. The two circular domains and the stripe domain correspond to the <math display="inline"> <semantics> <msub> <mi>L</mi> <mi>o</mi> </msub> </semantics> </math> phase, which is DPPC rich. The two separated domains on the surface of the striped domain and the connected domain on the surface of two circular domains correspond to the <math display="inline"> <semantics> <msub> <mi>L</mi> <mi>d</mi> </msub> </semantics> </math> phase, which is DOPC rich.</p> Full article ">Figure 4
<p>(<b>a</b>) The size <math display="inline"> <semantics> <msub> <mi>D</mi> <mn>2</mn> </msub> </semantics> </math> vs. <math display="inline"> <semantics> <msub> <mi>ϕ</mi> <mn>0</mn> </msub> </semantics> </math> at <math display="inline"> <semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>2</mn> </mrow> </semantics> </math>; (<b>b</b>) <math display="inline"> <semantics> <msub> <mi>D</mi> <mn>2</mn> </msub> </semantics> </math> vs. <span class="html-italic">λ</span> at <math display="inline"> <semantics> <mrow> <msub> <mi>ϕ</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>7</mn> </mrow> </semantics> </math>; and (<b>c</b>) the bending energy <math display="inline"> <semantics> <mrow> <msub> <mi>S</mi> <mn>2</mn> </msub> <mo>/</mo> <msub> <mi>N</mi> <mi>B</mi> </msub> </mrow> </semantics> </math> vs. <span class="html-italic">λ</span> at <math display="inline"> <semantics> <mrow> <mi>ϕ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>7</mn> </mrow> </semantics> </math>. These are calculated on the dashed horizontal and vertical lines in <a href="#polymers-08-00284-f003" class="html-fig">Figure 3</a>. The minor axis <math display="inline"> <semantics> <msub> <mi>D</mi> <mn>2</mn> </msub> </semantics> </math> and the bending energy <math display="inline"> <semantics> <mrow> <msub> <mi>S</mi> <mn>2</mn> </msub> <mo>/</mo> <msub> <mi>N</mi> <mi>B</mi> </msub> </mrow> </semantics> </math> change almost discontinuously and smoothly at the phase boundaries, which are denoted by the vertical dashed lines.</p> Full article ">Figure 5
<p>The surface size is characterized by three diameters <math display="inline"> <semantics> <msub> <mi>D</mi> <mn>1</mn> </msub> </semantics> </math>, <math display="inline"> <semantics> <msub> <mi>D</mi> <mn>2</mn> </msub> </semantics> </math> and <math display="inline"> <semantics> <msub> <mi>D</mi> <mn>3</mn> </msub> </semantics> </math>, where <math display="inline"> <semantics> <mrow> <msub> <mi>D</mi> <mn>1</mn> </msub> <mo>&gt;</mo> <msub> <mi>D</mi> <mn>2</mn> </msub> <mo>&gt;</mo> <msub> <mi>D</mi> <mn>3</mn> </msub> </mrow> </semantics> </math>. The three axes are perpendicular to each other.</p> Full article ">Figure 6
<p>A phase diagram of Model 2 on the <math display="inline"> <semantics> <mrow> <mi>λ</mi> <mo>−</mo> <msub> <mi>ϕ</mi> <mi>o</mi> </msub> </mrow> </semantics> </math> plane at <math display="inline"> <semantics> <mrow> <mi>κ</mi> <mo>=</mo> <mn>10</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>c</mi> <mo>=</mo> <mn>8</mn> <mo>.</mo> <mn>37</mn> </mrow> </semantics> </math> and the snapshots of surfaces obtained at the points indicated by the symbol (<math display="inline"> <semantics> <mrow> <mo mathcolor="red">×</mo> </mrow> </semantics> </math>). The solid lines on the phase diagram denote the phase boundaries, and the dashed lines denote the positions for the simulations for <a href="#polymers-08-00284-f007" class="html-fig">Figure 7</a>a–c. The solid circles (<math display="inline"> <semantics> <mrow> <mi mathcolor="red">•</mi> </mrow> </semantics> </math>) denote the data points of the simulations for the phase boundaries.</p> Full article ">Figure 7
<p>(<b>a</b>) The size <math display="inline"> <semantics> <msub> <mi>D</mi> <mn>2</mn> </msub> </semantics> </math> vs. <math display="inline"> <semantics> <msub> <mi>ϕ</mi> <mn>0</mn> </msub> </semantics> </math> at <math display="inline"> <semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> </mrow> </semantics> </math>; (<b>b</b>) <math display="inline"> <semantics> <msub> <mi>D</mi> <mn>2</mn> </msub> </semantics> </math> vs. <span class="html-italic">λ</span> at <math display="inline"> <semantics> <mrow> <msub> <mi>ϕ</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>8</mn> </mrow> </semantics> </math>; and (<b>c</b>) the bending energy <math display="inline"> <semantics> <mrow> <msub> <mi>S</mi> <mn>2</mn> </msub> <mo>/</mo> <msub> <mi>N</mi> <mi>B</mi> </msub> </mrow> </semantics> </math> vs. <math display="inline"> <semantics> <msub> <mi>ϕ</mi> <mn>0</mn> </msub> </semantics> </math> at <math display="inline"> <semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> </mrow> </semantics> </math>. These are calculated on the dashed horizontal and vertical lines in <a href="#polymers-08-00284-f006" class="html-fig">Figure 6</a>. The size of the surface changes almost discontinuously and smoothly at the phase boundaries, which are denoted by the dashed lines.</p> Full article ">Figure 8
<p>A phase diagram of Model 2 on the <math display="inline"> <semantics> <mrow> <mi>κ</mi> <mo>−</mo> <msub> <mi>ϕ</mi> <mi>o</mi> </msub> </mrow> </semantics> </math> plane at <math display="inline"> <semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>3</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>c</mi> <mo>=</mo> <mn>5</mn> </mrow> </semantics> </math> and the snapshots of surfaces obtained at the points indicated by the symbol (<math display="inline"> <semantics> <mrow> <mo mathcolor="red">×</mo> </mrow> </semantics> </math>). The solid lines on the phase diagram denote the phase boundaries. The solid circles (<math display="inline"> <semantics> <mrow> <mi mathcolor="red">•</mi> </mrow> </semantics> </math>) denote the data points of the simulations for the phase boundaries.</p> Full article ">Figure 9
<p>(<b>a</b>) The Gaussian energy <math display="inline"> <semantics> <mrow> <msub> <mi>S</mi> <mn>1</mn> </msub> <mo>/</mo> <mi>N</mi> </mrow> </semantics> </math> vs. <math display="inline"> <semantics> <msub> <mi>ϕ</mi> <mn>0</mn> </msub> </semantics> </math> at <math display="inline"> <semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>2</mn> </mrow> </semantics> </math>; (<b>b</b>) <math display="inline"> <semantics> <mrow> <msub> <mi>S</mi> <mn>1</mn> </msub> <mo>/</mo> <mi>N</mi> </mrow> </semantics> </math> vs. <span class="html-italic">λ</span> at <math display="inline"> <semantics> <mrow> <msub> <mi>ϕ</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>7</mn> </mrow> </semantics> </math> for Model 1; (<b>c</b>) <math display="inline"> <semantics> <mrow> <msub> <mi>S</mi> <mn>1</mn> </msub> <mo>/</mo> <mi>N</mi> </mrow> </semantics> </math> vs. <math display="inline"> <semantics> <msub> <mi>ϕ</mi> <mn>0</mn> </msub> </semantics> </math> at <math display="inline"> <semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> </mrow> </semantics> </math>; and (<b>d</b>) <math display="inline"> <semantics> <mrow> <msub> <mi>S</mi> <mn>1</mn> </msub> <mo>/</mo> <mi>N</mi> </mrow> </semantics> </math> vs. <span class="html-italic">λ</span> at <math display="inline"> <semantics> <mrow> <msub> <mi>ϕ</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>8</mn> </mrow> </semantics> </math> for Model 2. The data in (<b>a</b>) and (<b>b</b>) ((<b>c</b>) and (<b>d</b>)) are obtained on the dashed lines in <a href="#polymers-08-00284-f003" class="html-fig">Figure 3</a> (<a href="#polymers-08-00284-f006" class="html-fig">Figure 6</a>).</p> Full article ">Figure 10
<p>(<b>a</b>) A triangle <span class="html-italic">Δ</span> included in a triangulated sphere in <math display="inline"> <semantics> <msup> <mi>ℜ</mi> <mn>3</mn> </msup> </semantics> </math>; (<b>b</b>) the three nearest neighbor triangles of <span class="html-italic">Δ</span> and the unit normal vectors <math display="inline"> <semantics> <msub> <mi mathvariant="bold">n</mi> <mn>0</mn> </msub> </semantics> </math>, <math display="inline"> <semantics> <msub> <mi mathvariant="bold">n</mi> <mn>1</mn> </msub> </semantics> </math>, <math display="inline"> <semantics> <msub> <mi mathvariant="bold">n</mi> <mn>2</mn> </msub> </semantics> </math> and <math display="inline"> <semantics> <msub> <mi mathvariant="bold">n</mi> <mn>3</mn> </msub> </semantics> </math>; and (<b>c</b>) the triangle orientation that defines the direction-dependent bond potential <math display="inline"> <semantics> <mrow> <msub> <mi>γ</mi> <mn>12</mn> </msub> <msubsup> <mi>ℓ</mi> <mrow> <mn>12</mn> </mrow> <mn>2</mn> </msubsup> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <msub> <mi>γ</mi> <mn>21</mn> </msub> <msubsup> <mi>ℓ</mi> <mrow> <mn>21</mn> </mrow> <mn>2</mn> </msubsup> </mrow> </semantics> </math> of the bond 12, where <math display="inline"> <semantics> <mrow> <msub> <mi>ℓ</mi> <mn>12</mn> </msub> <mo>=</mo> <msub> <mi>ℓ</mi> <mn>21</mn> </msub> </mrow> </semantics> </math>.</p> Full article ">Figure 11
<p>Local coordinate origins of the triangles <math display="inline"> <semantics> <msup> <mrow> <mi>Δ</mi> </mrow> <mo>+</mo> </msup> </semantics> </math> and <math display="inline"> <semantics> <msup> <mrow> <mi>Δ</mi> </mrow> <mo>−</mo> </msup> </semantics> </math> for <math display="inline"> <semantics> <mrow> <msub> <mi>S</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <msub> <mi>ℓ</mi> <mn>12</mn> </msub> <mo>)</mo> </mrow> </mrow> </semantics> </math> and the elements of <math display="inline"> <semantics> <msub> <mi>γ</mi> <mn>12</mn> </msub> </semantics> </math> and <math display="inline"> <semantics> <msub> <mi>γ</mi> <mn>21</mn> </msub> </semantics> </math> of the configurations of (<b>a</b>) the original and (<b>b</b>) the inside out (inside view).</p> Full article ">
7678 KiB  
Article
Microscopic Dynamics and Topology of Polymer Rings Immersed in a Host Matrix of Longer Linear Polymers: Results from a Detailed Molecular Dynamics Simulation Study and Comparison with Experimental Data
by George D. Papadopoulos, Dimitrios G. Tsalikis and Vlasis G. Mavrantzas
Polymers 2016, 8(8), 283; https://doi.org/10.3390/polym8080283 - 4 Aug 2016
Cited by 33 | Viewed by 7940
Abstract
We have performed molecular dynamics (MD) simulations of melt systems consisting of a small number of long ring poly(ethylene oxide) (PEO) probes immersed in a host matrix of linear PEO chains and have studied their microscopic dynamics and topology as a function of [...] Read more.
We have performed molecular dynamics (MD) simulations of melt systems consisting of a small number of long ring poly(ethylene oxide) (PEO) probes immersed in a host matrix of linear PEO chains and have studied their microscopic dynamics and topology as a function of the molecular length of the host linear chains. Consistent with a recent neutron spin echo spectroscopy study (Goossen et al., Phys. Rev. Lett. 2015, 115, 148302), we have observed that the segmental dynamics of the probe ring molecules is controlled by the length of the host linear chains. In matrices of short, unentangled linear chains, the ring probes exhibit a Rouse-like dynamics, and the spectra of their dynamic structure factor resemble those in their own melt. In striking contrast, in matrices of long, entangled linear chains, their dynamics is drastically altered. The corresponding dynamic structure factor spectra exhibit a steep initial decay up to times on the order of the entanglement time ?e of linear PEO at the same temperature but then they become practically time-independent approaching plateau values. The plateau values are different for different wavevectors; they also depend on the length of the host linear chains. Our results are supported by a geometric analysis of topological interactions, which reveals significant threading of all ring molecules by the linear chains. In most cases, each ring is simultaneously threaded by several linear chains. As a result, its dynamics at times longer than a few ?e should be completely dictated by the release of the topological restrictions imposed by these threadings (interpenetrations). Our topological analysis did not indicate any effect of the few ring probes on the statistical properties of the network of primitive paths of the host linear chains. Full article
(This article belongs to the Special Issue Semiflexible Polymers)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Dependence of: (<b>a</b>) <math display="inline"> <semantics> <mrow> <mrow> <mo>〈</mo> <mrow> <msubsup> <mi>R</mi> <mrow> <mi mathvariant="normal">g</mi> <mo>,</mo> <mi mathvariant="normal">R</mi> </mrow> <mn>2</mn> </msubsup> </mrow> <mo>〉</mo> </mrow> </mrow> </semantics> </math>, (<b>b</b>) <math display="inline"> <semantics> <mrow> <mrow> <mo>〈</mo> <mrow> <msubsup> <mi>R</mi> <mrow> <mi mathvariant="normal">g</mi> <mo>,</mo> <mi mathvariant="normal">L</mi> </mrow> <mn>2</mn> </msubsup> </mrow> <mo>〉</mo> </mrow> </mrow> </semantics> </math>, (<b>c</b>) <math display="inline"> <semantics> <mrow> <mrow> <mo>〈</mo> <mrow> <msubsup> <mi>R</mi> <mi mathvariant="normal">d</mi> <mn>2</mn> </msubsup> </mrow> <mo>〉</mo> </mrow> </mrow> </semantics> </math> and (<b>d</b>) <math display="inline"> <semantics> <mrow> <mrow> <mo>〈</mo> <mrow> <msubsup> <mi>R</mi> <mrow> <mi>ee</mi> </mrow> <mn>2</mn> </msubsup> </mrow> <mo>〉</mo> </mrow> </mrow> </semantics> </math> on the chain length <span class="html-italic">N</span><sub>L</sub> (L stands for linear) of the host linear chains. Results are also shown for the same quantities in the corresponding pure melts.</p> Full article ">Figure 2
<p>MD simulation predictions (symbols) for the probability distribution function of: (<b>a</b>) the magnitude of the end-to-end distance vector for the pure linear PEO-02k and PEO-10k melts; and (<b>b</b>) the magnitude of the diameter vector for the ring PEO-20k molecules in their own melt and in the L-20k blend. For comparison (lines), we also show the distributions according to the analytical expression, Equation (1), using the values of <math display="inline"> <semantics> <mrow> <mrow> <mo>〈</mo> <mrow> <msup> <mi>R</mi> <mn>2</mn> </msup> </mrow> <mo>〉</mo> </mrow> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mrow> <mo>〈</mo> <mrow> <msubsup> <mi>R</mi> <mi mathvariant="normal">d</mi> <mn>2</mn> </msubsup> </mrow> <mo>〉</mo> </mrow> </mrow> </semantics> </math> computed from the MD simulations.</p> Full article ">Figure 3
<p>The squared amplitudes of the Rouse normal modes <math display="inline"> <semantics> <mrow> <mrow> <mo>〈</mo> <mrow> <msub> <mi mathvariant="bold">X</mi> <mi mathvariant="normal">p</mi> </msub> <msup> <mrow> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> <mn>2</mn> </msup> </mrow> <mo>〉</mo> </mrow> </mrow> </semantics> </math> for the ring molecules in the three blends and in a pure ring PEO-20k melt as a function of <math display="inline"> <semantics> <mrow> <mfrac bevelled="true"> <mi>N</mi> <mrow> <msup> <mi>p</mi> <mn>2</mn> </msup> </mrow> </mfrac> </mrow> </semantics> </math> in a log–log plot. The dashed line has been drawn with a slope of 1 as a guide for the eye and corresponds to the Rouse scaling.</p> Full article ">Figure 4
<p>Log-linear plots of the normalized time autocorrelation functions of several Rouse modes for the PEO-20k ring molecules in: (<b>a</b>) the L-02k blend, (<b>b</b>) the L-10k blend, (<b>c</b>) the L-20k blend, and (<b>d</b>) the pure ring PEO-20k melt.</p> Full article ">Figure 5
<p>The scaling of the characteristic times <math display="inline"> <semantics> <mrow> <msub> <mi mathvariant="bold-italic">τ</mi> <mi mathvariant="normal">p</mi> </msub> </mrow> </semantics> </math> describing the relaxation of the Rouse normal modes <span class="html-italic">p</span> with chain length <span class="html-italic">N</span>. The dashed line indicates the Rouse model, namely, <math display="inline"> <semantics> <mrow> <msub> <mi mathvariant="bold-italic">τ</mi> <mi mathvariant="normal">p</mi> </msub> <mo>~</mo> <msup> <mrow> <mrow> <mo>(</mo> <mrow> <mfrac bevelled="true"> <mi>N</mi> <mi>p</mi> </mfrac> </mrow> <mo>)</mo> </mrow> </mrow> <mn>2</mn> </msup> </mrow> </semantics> </math>, and has been drawn as a guide for the eye.</p> Full article ">Figure 6
<p>Computed (continuous or dashed lines) and experimentally measured (diamonds) <math display="inline"> <semantics> <mrow> <mfrac> <mrow> <mi>S</mi> <mo stretchy="false">(</mo> <mi>q</mi> <mo>,</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mi>S</mi> <mo stretchy="false">(</mo> <mi>q</mi> <mo>,</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> </mfrac> </mrow> </semantics> </math> plots for several wavenumbers <span class="html-italic">q</span>, for: (<b>a<sub>1</sub></b>) ring molecules in the L-02k blend together with data from Reference [<a href="#B21-polymers-08-00283" class="html-bibr">21</a>]; (<b>a<sub>2</sub></b>) ring molecules in the L-02k blend and in the pure PEO-20k ring melt (dashed lines); (<b>b</b>) ring molecules in the L-10k blend; and (<b>c</b>) ring molecules in the L-20k blend together with data from Reference [<a href="#B21-polymers-08-00283" class="html-bibr">21</a>].</p> Full article ">Figure 6 Cont.
<p>Computed (continuous or dashed lines) and experimentally measured (diamonds) <math display="inline"> <semantics> <mrow> <mfrac> <mrow> <mi>S</mi> <mo stretchy="false">(</mo> <mi>q</mi> <mo>,</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mi>S</mi> <mo stretchy="false">(</mo> <mi>q</mi> <mo>,</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> </mfrac> </mrow> </semantics> </math> plots for several wavenumbers <span class="html-italic">q</span>, for: (<b>a<sub>1</sub></b>) ring molecules in the L-02k blend together with data from Reference [<a href="#B21-polymers-08-00283" class="html-bibr">21</a>]; (<b>a<sub>2</sub></b>) ring molecules in the L-02k blend and in the pure PEO-20k ring melt (dashed lines); (<b>b</b>) ring molecules in the L-10k blend; and (<b>c</b>) ring molecules in the L-20k blend together with data from Reference [<a href="#B21-polymers-08-00283" class="html-bibr">21</a>].</p> Full article ">Figure 7
<p>Log–log plot of the segmental mean-square displacement of ring PEO-20k molecules with time <span class="html-italic">t</span> in the three blends and in their own melt.</p> Full article ">Figure 8
<p>Log–log plot of the mean-square displacement of atomistic segments of linear chains with time <span class="html-italic">t</span> in: (<b>a</b>) the L-02k blend and the pure linear PEO-02k melt, (<b>b</b>) the L-10k blend and the pure linear PEO-10k melt, and (<b>c</b>) the L-20k blend and the pure linear PEO-20k.</p> Full article ">Figure 9
<p>Log–log plot of the mean-square displacement of the centers-of-mass of ring molecules (<b>a</b>) and linear chains (<b>b</b>) with time <span class="html-italic">t</span> for all simulated systems.</p> Full article ">Figure 10
<p>Average number of linear chains that thread a ring molecule in the three blends.</p> Full article ">Figure 11
<p>(<b>a</b>) Percentage of linear chains that are involved in threading events with ring molecules in the three blends; and (<b>b</b>) percentage of linear chains involved in multiple threading events.</p> Full article ">Figure 12
<p>Examples of multiple threading. The snapshots have been taken from the combined geometric/topological analysis of: (<b>a</b>) the L-02k blend, and (<b>b</b>) the L-20k blend. (<b>a</b>) The blue ring molecule is simultaneously threaded by fifteen linear chains. (<b>b</b>) The blue ring chain is simultaneously threaded by ten linear chains (here, for simplicity, only the PP of the red linear chain is shown in full; for all other linear chains, only the part of their PP whose strands are involved in the threading is shown).</p> Full article ">Figure 13
<p>Calculation of the tube diameter <span class="html-italic">d<sub>t</sub></span> based on the segmental mean-square displacement of the innermost chain segments <math display="inline"> <semantics> <mrow> <mi>ϕ</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mrow> <mo>〈</mo> <mrow> <msup> <mrow> <mrow> <mo>(</mo> <mrow> <msub> <mstyle mathvariant="bold" mathsize="normal"> <mi>r</mi> </mstyle> <mi mathvariant="normal">n</mi> </msub> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo>−</mo> <msub> <mstyle mathvariant="bold" mathsize="normal"> <mi>r</mi> </mstyle> <mi mathvariant="normal">n</mi> </msub> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> <mo>)</mo> </mrow> </mrow> <mn>2</mn> </msup> </mrow> <mo>〉</mo> </mrow> </mrow> </semantics> </math> versus time <span class="html-italic">t</span>. The tube diameter is estimated as <math display="inline"> <semantics> <mrow> <msub> <mi>d</mi> <mi mathvariant="normal">t</mi> </msub> <mo>=</mo> <mn>2</mn> <msqrt> <mrow> <mi>ϕ</mi> <mrow> <mo>(</mo> <mrow> <msup> <mi>t</mi> <mo>*</mo> </msup> </mrow> <mo>)</mo> </mrow> </mrow> </msqrt> </mrow> </semantics> </math> where <math display="inline"> <semantics> <mrow> <mi>ϕ</mi> <mo stretchy="false">(</mo> <msup> <mi>t</mi> <mo>*</mo> </msup> <mo stretchy="false">)</mo> </mrow> </semantics> </math> is computed at time <math display="inline"> <semantics> <mrow> <mi>t</mi> <mo>=</mo> <msup> <mi>t</mi> <mo>*</mo> </msup> </mrow> </semantics> </math> where the first break is observed as segments leave the initial <span class="html-italic">t</span><sup>1/2</sup> regime to enter the next <span class="html-italic">t</span><sup>1/4</sup> regime.</p> Full article ">
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Article
Enhanced Anti-Ultraviolet and Thermal Stability of a Pesticide via Modification of a Volatile Organic Compound (VOC)-Free Vinyl-Silsesquioxane in Desert Areas
by Derong Lin, Maozhu Kong, Liangyu Li, Xindan Li and Xingwen Zhang
Polymers 2016, 8(8), 282; https://doi.org/10.3390/polym8080282 - 4 Aug 2016
Cited by 1 | Viewed by 5624
Abstract
Due to the effect of severe environmental conditions, such as intense heat, blowing sand, and ultraviolet light, conventional pesticide applications have repeatedly failed to adequately control mosquito and sandfly populations in desert areas. In this study, a vinyl silsesquioxane (VS) was added to [...] Read more.
Due to the effect of severe environmental conditions, such as intense heat, blowing sand, and ultraviolet light, conventional pesticide applications have repeatedly failed to adequately control mosquito and sandfly populations in desert areas. In this study, a vinyl silsesquioxane (VS) was added to a pesticide (citral) to enhance residual, thermal and anti-ultraviolet properties via three double-bond reactions in the presence of an initiator: (1) the connection of VS and citral, (2) a radical self-polymerization of VS and (3) a radical self-polymerization of citral. VS-citral, the expected and main product of the copolymerization of VS and citral, was characterized using standard spectrum techniques. The molecular consequences of the free radical polymerization were analyzed by MALDITOF spectrometry. Anti-ultraviolet and thermal stability properties of the VS-citral system were tested using scanning spectrophotometry (SSP) and thermogravimetric analysis (TGA). The repellency of VS-citral decreased over time, from 97.63% at 0 h to 72.98% at 1 h and 60.0% at 2 h, as did the repellency of citral, from 89.56% at 0 h to 62.73% at 1 h and 50.95% at 2 h. Full article
(This article belongs to the Special Issue Hybrid Polymeric Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>FTIR spectra of (<b>a</b>) citral, (<b>b</b>) VS and (<b>c</b>) VS-citral.</p> Full article ">Figure 2
<p>MALDI-TOF mass spectra in the <span class="html-italic">m</span>/<span class="html-italic">z</span> = 925.2–1590.3 Da range correspond to the VS-citral oligomers.</p> Full article ">Figure 3
<p>The transparency of citral (<b>a</b>) and VS-citral (<b>b</b>) measured in the range of the UV-A and UV-B region (280–400 nm).</p> Full article ">Figure 4
<p>The thermal gravimetric (TG) curves of citral (<b>a</b>) and VS-citral (<b>b</b>) under the conditions of an increased speed of 20 °C/min and a temperature range of 0–800 °C.</p> Full article ">Scheme 1
<p>The copolymerization (1) for the connection of VS and 3 citrals, indicating that the reaction of the VS and citral favors their connection in the blend of VS, citral and a suitable initiator.</p> Full article ">Scheme 2
<p>The polarity effects on the double bonds of both VS and citral for the connection: Si is an electron-attracting atom and C is an electro-donating atom, which two C atoms in the VS and citral possess positive and negative charges, respectively.</p> Full article ">Scheme 3
<p>One supposed sample of McLafferty Rearrangement (mass spectrometry), deleting an enolic fragment (mass: 44) and leaving the rest of the parts in the VS-citral.</p> Full article ">
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