[go: up one dir, main page]
More Web Proxy on the site http://driver.im/
Next Issue
Volume 9, May
Previous Issue
Volume 9, March
You seem to have javascript disabled. Please note that many of the page functionalities won't work as expected without javascript enabled.
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
8.0
4.7
Journals
Polymers
Volume 9
Issue 4
polymers-logo

Journal Menu

► Journal Menu

Journal Browser

► Journal Browser
share announcement

Polymers, Volume 9, Issue 4 (April 2017) – 37 articles

Cover Story (view full-size image): This cover image highlights different molecular structures of single-walled carbon nanotube (SWCNT) buckypapers. The SWCNT length is found to have a pronounced impact on the structure of buckypapers. When the SWCNTs are short, they tend to form short bundles and to be tightly packed, exhibit high density and small pores, while long SWCNTs are entangled together at a low density accompanied by large pores. These structure variations contribute to distinct viscoelasticities of buckypapers. The energy dissipation for buckypapers with long SWCNTs under cyclic shear is dominated by the zipping–unzipping mechanism, while the sliding-friction mechanism controls the energy dissipation between short SWCNTs. By Ying Li. View this paper
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
3874 KiB  
Review
Stimuli-Regulated Smart Polymeric Systems for Gene Therapy
by Ansuja Pulickal Mathew, Ki-Hyun Cho, Saji Uthaman, Chong-Su Cho and In-Kyu Park
Polymers 2017, 9(4), 152; https://doi.org/10.3390/polym9040152 - 24 Apr 2017
Cited by 31 | Viewed by 9221
Abstract
The physiological condition of the human body is a composite of different environments, each with its own parameters that may differ under normal, as well as diseased conditions. These environmental conditions include factors, such as pH, temperature and enzymes that are specific to [...] Read more.
The physiological condition of the human body is a composite of different environments, each with its own parameters that may differ under normal, as well as diseased conditions. These environmental conditions include factors, such as pH, temperature and enzymes that are specific to a type of cell, tissue or organ or a pathological state, such as inflammation, cancer or infection. These conditions can act as specific triggers or stimuli for the efficient release of therapeutics at their destination by overcoming many physiological and biological barriers. The efficacy of conventional treatment modalities can be enhanced, side effects decreased and patient compliance improved by using stimuli-responsive material that respond to these triggers at the target site. These stimuli or triggers can be physical, chemical or biological and can be internal or external in nature. Many smart/intelligent stimuli-responsive therapeutic gene carriers have been developed that can respond to either internal stimuli, which may be normally present, overexpressed or present in decreased levels, owing to a disease, or to stimuli that are applied externally, such as magnetic fields. This review focuses on the effects of various internal stimuli, such as temperature, pH, redox potential, enzymes, osmotic activity and other biomolecules that are present in the body, on modulating gene expression by using stimuli-regulated smart polymeric carriers. Full article
(This article belongs to the Special Issue Polymers and Nanogels for Gene Therapy)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Different intracellular stimuli (ROS, intracellular enzymes, redox condition and osmotic activity) mediated release of gene carriers and subsequent gene release inside cellular environment.</p> Full article ">Figure 2
<p>(<b>a</b>) The number of scientific papers published over the past decade on internal stimuli-based gene delivery (source: ISI Web of Knowledge: The Thompson Corporation; search terms: “internal stimuli/gene delivery”; date of search: February 2017). (<b>b</b>) The number of scientific papers published over the past decade on internal stimuli-based drug delivery systems (source: ISI Web of Knowledge: The Thompson Corporation; search terms: “internal stimuli/drug delivery”; date of search: February 2017).</p> Full article ">Figure 3
<p>(<b>A</b>) Schematic of the pH-sensitive charge/size dual-rebound gene delivery system. (<b>B</b>) Transfection efficiency of PEG((PLG/PEI)/DNA) [P((GP)D)] with various PEG mass ratios at different pH values (7.4 and 6.8) in CT26 cells for 2 h. (<b>C</b>) Mean fluorescence intensity of cellular uptake of polyethylenimine (PEI)/DNA (PD), poly(<span class="html-small-caps">l</span>-glutamate) (PLG)/(PEI/DNA) (G(PD)), (PLG/PEI)/DNA((GP)D) and PEG((PLG/PEI)/DNA)(P(GP)D) at different pH values (7.4 and 6.8). (<b>D</b>) CLSM images of CT26 cells incubated with D, PD, G(PD), (GP)D and P((GP)D) at different pH values (7.4 and 6.8); Cy5-DNA was tracked. Reproduced with permission from [<a href="#B46-polymers-09-00152" class="html-bibr">46</a>]. Copyright proceedings from the American Chemical Society, 2015.</p> Full article ">Figure 3 Cont.
<p>(<b>A</b>) Schematic of the pH-sensitive charge/size dual-rebound gene delivery system. (<b>B</b>) Transfection efficiency of PEG((PLG/PEI)/DNA) [P((GP)D)] with various PEG mass ratios at different pH values (7.4 and 6.8) in CT26 cells for 2 h. (<b>C</b>) Mean fluorescence intensity of cellular uptake of polyethylenimine (PEI)/DNA (PD), poly(<span class="html-small-caps">l</span>-glutamate) (PLG)/(PEI/DNA) (G(PD)), (PLG/PEI)/DNA((GP)D) and PEG((PLG/PEI)/DNA)(P(GP)D) at different pH values (7.4 and 6.8). (<b>D</b>) CLSM images of CT26 cells incubated with D, PD, G(PD), (GP)D and P((GP)D) at different pH values (7.4 and 6.8); Cy5-DNA was tracked. Reproduced with permission from [<a href="#B46-polymers-09-00152" class="html-bibr">46</a>]. Copyright proceedings from the American Chemical Society, 2015.</p> Full article ">Figure 4
<p>Schematic illustration of multifunctional aminoglycosides-based hyperbranched polymers (HPs) with antibacterial activity, biocompatibility and gene transfection capability. Reproduced with permission from [<a href="#B80-polymers-09-00152" class="html-bibr">80</a>]. Copyright proceedings from Biomaterials, Elsevier, November 2016.</p> Full article ">Figure 5
<p>Schematic illustration showing PEG-coated polyplex micelles in MMP-2-expressing tumor tissue showing enhanced cellular uptake and endosomal escape for gene transfection. Reproduced with permission from [<a href="#B107-polymers-09-00152" class="html-bibr">107</a>]. Copyright proceedings from The Royal Society of Chemistry.</p> Full article ">Figure 6
<p>Schematic representation of the synthesis of PSOAT. Reproduced with permission from [<a href="#B115-polymers-09-00152" class="html-bibr">115</a>]. Copyright proceedings from Elsevier.</p> Full article ">Figure 7
<p>Effects of (<b>A</b>) chlorpromazine, (<b>B</b>) β-methyl cyclodextrin, (<b>C</b>) genistein and (<b>D</b>) wortmannin on transfection efficiency in A549 cells. Reproduced with permission from [<a href="#B116-polymers-09-00152" class="html-bibr">116</a>]. Copyright proceedings from the American Chemical Society.</p> Full article ">Figure 8
<p>Schematic representation of the synthesis of poly (mannitol-<span class="html-italic">co</span>-PEI) (PMT). Reproduced with permission from [<a href="#B122-polymers-09-00152" class="html-bibr">122</a>] Copyright proceedings from Elsevier).</p> Full article ">Figure 9
<p>Fluorescent microscopy images showing lysosome staining (red) and FITC-PEI/DNA polyplexes (green); (<b>a</b>) Polyplex with FITC (<b>b</b>) Colocalization spot using the Image J program; (<b>c</b>) overlay of lysosomes and polyplexes (yellow). Scale bar represents 5 μm. Reproduced with permission from [<a href="#B122-polymers-09-00152" class="html-bibr">122</a>]. Copyright proceedings from Elsevier).</p> Full article ">
5990 KiB  
Article
Mechanical Behavior of Hybrid Glass/Steel Fiber Reinforced Epoxy Composites
by Amanda K. McBride, Samuel L. Turek, Arash E. Zaghi and Kelly A. Burke
Polymers 2017, 9(4), 151; https://doi.org/10.3390/polym9040151 - 23 Apr 2017
Cited by 33 | Viewed by 11280
Abstract
While conventional fiber-reinforced polymer composites offer high strength and stiffness, they lack ductility and the ability to absorb energy before failure. This work investigates hybrid fiber composites for structural applications comprised of polymer, steel fiber, and glass fibers to address this shortcoming. Varying [...] Read more.
While conventional fiber-reinforced polymer composites offer high strength and stiffness, they lack ductility and the ability to absorb energy before failure. This work investigates hybrid fiber composites for structural applications comprised of polymer, steel fiber, and glass fibers to address this shortcoming. Varying volume fractions of thin, ductile steel fibers were introduced into glass fiber reinforced epoxy composites. Non-hybrid and hybrid composite specimens were prepared and subjected to monolithic and half-cyclic tensile testing to obtain stress-strain relationships, hysteresis behavior, and insight into failure mechanisms. Open-hole testing was used to assess the vulnerability of the composites to stress concentration. Incorporating steel fibers into glass/epoxy composites offered a significant improvement in energy absorption prior to failure and material re-centering capabilities. It was found that a lower percentage of steel fibers (8.2%) in the hybrid composite outperformed those with higher percentages (15.7% and 22.8%) in terms of energy absorption and re-centering, as the glass reinforcement distributed the plasticity over a larger area. A bilinear hysteresis model was developed to predict cyclic behavior of the hybrid composite. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Reinforcement types: (<b>a</b>) UD glass fibers; (<b>b</b>) UD steel fibers.</p> Full article ">Figure 2
<p>Composite preparation: (<b>a</b>) Fiber hand lay-up; (<b>b</b>) cured composite plates; (<b>c)</b> coupon dimensions with end tabs.</p> Full article ">Figure 3
<p>Monolithic tensile stress-strain relationships of specimens with no holes.</p> Full article ">Figure 4
<p>[SGGGGS] hybrid composite curve. (Inset) The linear region expanded from the encircled region.</p> Full article ">Figure 5
<p>[SGSGSGS] hybrid composite curve. (Inset) The linear region expanded from the encircled region.</p> Full article ">Figure 6
<p>[SSSGSSS] hybrid composite curve. (Inset) The linear region expanded from the encircled region.</p> Full article ">Figure 7
<p>Images of failure specimens: (<b>a</b>) [G]<sub>5</sub>; (<b>b</b>) [SGGGGS]; (<b>c</b>) [SGSGSGS]; (<b>d</b>) [SSSGSSS]; (<b>e</b>) [S]<sub>8</sub>.</p> Full article ">Figure 8
<p>UD steel composite crack bridging and necking at matrix crack. Image taken by Carson digital handheld microscope.</p> Full article ">Figure 9
<p>Tensile stress-strain relationships of specimens without holes and with holes (denoted by the label “OHT”).</p> Full article ">Figure 10
<p>Stress-strain relationships of specimens with open-holes during monolithic tensile (denoted OHT) and half-cyclic loading (denoted OHC).</p> Full article ">Figure 11
<p>Area under the curve of half-cyclic loading for [SSSGSSS]. The seventh loading cycle is demonstrated by an arrow.</p> Full article ">Figure 12
<p>Energy dissipation of composites during open-hole half-cyclic loading: (<b>a</b>) calculated energy values; (<b>b</b>) normalized energy values per 1% of steel. (Note) Percentage along curves represents the steel fiber fraction in the composite. Lines connecting points used to display trend.</p> Full article ">Figure 13
<p>Residual strain ratio of composites during open-hole half-cyclic loading. Note: Percentage along curves represents the steel fiber fraction in the composite. The lines connecting points are used to display trends.</p> Full article ">Figure 14
<p>Lead-rubber bearing ideal bilinear hysteresis behavior.</p> Full article ">Figure 15
<p>Ideal hysteresis behavior: (<b>a</b>) [SGGGGS]; (<b>b</b>) [SGSGSGS]; (<b>c</b>) [SSSGSSS]; (<b>d</b>) [S]<sub>8</sub>.</p> Full article ">
7428 KiB  
Review
Electrical and Electrochemical Properties of Conducting Polymers
by Thanh-Hai Le, Yukyung Kim and Hyeonseok Yoon
Polymers 2017, 9(4), 150; https://doi.org/10.3390/polym9040150 - 23 Apr 2017
Cited by 826 | Viewed by 46080
Abstract
Conducting polymers (CPs) have received much attention in both fundamental and practical studies because they have electrical and electrochemical properties similar to those of both traditional semiconductors and metals. CPs possess excellent characteristics such as mild synthesis and processing conditions, chemical and structural [...] Read more.
Conducting polymers (CPs) have received much attention in both fundamental and practical studies because they have electrical and electrochemical properties similar to those of both traditional semiconductors and metals. CPs possess excellent characteristics such as mild synthesis and processing conditions, chemical and structural diversity, tunable conductivity, and structural flexibility. Advances in nanotechnology have allowed the fabrication of versatile CP nanomaterials with improved performance for various applications including electronics, optoelectronics, sensors, and energy devices. The aim of this review is to explore the conductivity mechanisms and electrical and electrochemical properties of CPs and to discuss the factors that significantly affect these properties. The size and morphology of the materials are also discussed as key parameters that affect their major properties. Finally, the latest trends in research on electrochemical capacitors and sensors are introduced through an in-depth discussion of the most remarkable studies reported since 2003. Full article
(This article belongs to the Special Issue Conductive Polymers 2017)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The structure of polyacetylene: The backbone contains conjugated double bonds.</p> Full article ">Figure 2
<p>The electronic band and chemical structures of polythiophene (PT) with (<b>a</b>) <span class="html-italic">p</span>-type doping and (<b>b</b>) <span class="html-italic">n</span>-type doping.</p> Full article ">Figure 3
<p>Electronic bands and chemical structures illustrating (<b>a</b>) undoped; (<b>b</b>) polaron; (<b>c</b>) bipolaron; and (<b>d</b>) fully doped states of polypyrrole (PPy).</p> Full article ">Figure 4
<p>(<b>a</b>) Schematic illustration of the geometric structure of a neutral soliton on a trans-polyacetylene chain; (<b>b</b>) A soliton band with light doping (left) and heavy doping (right); The band structure of trans-polyacetylene containing (<b>c</b>) a positively charged soliton; (<b>d</b>) a neutral soliton; and (<b>e</b>) a negatively charged soliton.</p> Full article ">Figure 5
<p>The general conductivity range of conducting polymers (CPs).</p> Full article ">Figure 6
<p>Cyclic voltammograms of a poly(<span class="html-italic">N</span>-phenyl-1-naphthylamine) film on Pt in 1 M LiClO<sub>4</sub>/CH<sub>3</sub>CN solution at different scanning rates. Reprinted with permission from [<a href="#B85-polymers-09-00150" class="html-bibr">85</a>]. Copyright 1990, American Chemical Society.</p> Full article ">Figure 7
<p>Cyclic voltammetry (CV) curves of a polyaniline (PANI) film doped with hydrochloric acid or sulfuric acid at the same potential scan rate 50 mV·s<sup>−1</sup>.</p> Full article ">Figure 8
<p>CV analysis of PANI nanostructures with three different shapes (nanosphere, NS; nanorods, NR; and nanofibers, NF) performed in a 1 M sulfuric acid solution. (<b>a</b>) Cyclic voltammograms of electrodes consisting of PANI nanostructures at the same scan rate (25 mV·s<sup>−1</sup>); (<b>b</b>) plots of the peak current (the anodic peak current, <span class="html-italic">I</span><sub>pa</sub>; the cathodic peak current, <span class="html-italic">I</span><sub>pc</sub>) vs. the scan rate; and (<b>c</b>) plots of the peak potential (the anodic peak potential, <span class="html-italic">E</span><sub>pa</sub>; the cathodic peak current, <span class="html-italic">E</span><sub>pc</sub>) vs. the log of the scan rate. With permission from [<a href="#B86-polymers-09-00150" class="html-bibr">86</a>]; Copyright 2012, American Chemical Society.</p> Full article ">Figure 9
<p>Mechanism of electrochemo-mechanical actuation in CPs. (<b>a, c, e</b>) Volume changes in CP via (<b>b</b>, <b>d</b>) two different redox pathways.</p> Full article ">Figure 10
<p>The different redox/protonation states and colors of PANI.</p> Full article ">Figure 11
<p>Field-emission scanning electron microscope images of PANI nanostructures with different aspect ratios synthesized under the same stirring conditions (200 rpm) and histograms showing their size distribution (<span class="html-italic">D</span>, diameter; <span class="html-italic">L</span>, length): (<b>a</b>) nanospheres; (<b>b</b>) nanorods; and (<b>c</b>) nanofibers. With permission from [<a href="#B86-polymers-09-00150" class="html-bibr">86</a>]; Copyright 2012, American Chemical Society.</p> Full article ">Figure 12
<p>Effect of binary nanoparticle packing on electrode performance. Ternary diagrams for nanospheres of three different diameters showing the distribution of (<b>a</b>,<b>b</b>) specific capacitance and (<b>c</b>,<b>d</b>) coulombic efficiency as a function of the mixed weight fraction (<span class="html-italic">f</span><sub>m</sub>) measured at (<b>a</b>,<b>c</b>) 0.1 A·g<sup>−1</sup> and (<b>b</b>,<b>d</b>) 1.0 A·g<sup>−1</sup>. A three-electrode system was used with 1 M sulfuric acid solution. The <span class="html-italic">E</span><sub>c</sub> values were calculated from the charge/discharge curves. Reprinted with permission from [<a href="#B123-polymers-09-00150" class="html-bibr">123</a>]. Copyright 2016, Royal Society of Chemistry.</p> Full article ">Figure 13
<p>(<b>a</b>) Schematic illustration of the formation of graphene/PANI multilayered nanostructures (GPMNs) by direct physical exfoliation of graphite with PANI glue; (<b>b</b>) photographs showing the long-term colloidal stability of a GPMN dispersion solution in the absence (<b>left</b>) and presence (<b>right</b>) of PANI glue. GPMNs showed outstanding colloidal stability in both NMP and water. Reprinted with permission from [<a href="#B126-polymers-09-00150" class="html-bibr">126</a>]. Copyright 2015, John Wiley &amp; Sons.</p> Full article ">Figure 14
<p>Schematic of the synthetic procedure for NiCo<sub>2</sub>O<sub>4</sub>@PANI nanorod arrays. Reprinted with permission from [<a href="#B134-polymers-09-00150" class="html-bibr">134</a>]. Copyright 2016, American Chemical Society.</p> Full article ">Figure 15
<p>Real-time response of PPy/cellulose (PPCL) composite membranes in a flow cell measured at different applied potentials: (<b>a</b>) Hg(II); (<b>b</b>) Ag(I); (<b>c</b>) Pb(II); (<b>d</b>) Ni(II); (<b>e</b>) Cd(II); (<b>f</b>) Cr(III); and (<b>g</b>) Zn(II). Reprinted with permission from [<a href="#B152-polymers-09-00150" class="html-bibr">152</a>]. Copyright 2014, Royal Society of Chemistry.</p> Full article ">Figure 16
<p>Schematic illustrating (<b>a</b>) the alternating layered structure of graphene/PANI; (<b>b</b>) the series connection and parallel connection-like structures formed by different orientations of the graphene/PANI film between the electrodes; and (<b>c</b>,<b>d</b>) the resistometric sensor setup for measuring the electrical response of the graphene/PANI films (electrode, blue; PANI, green; graphene, black). Reprinted with permission from [<a href="#B153-polymers-09-00150" class="html-bibr">153</a>]. Copyright 2016, American Chemical Society.</p> Full article ">Figure 17
<p>Schematic illustration of the reaction steps for the fabrication of a field-effect transistor (FET) sensor platform based on carboxylated PPy nanotubes (CPNTs): (<b>a</b>) microelectrode substrate; (<b>b</b>) aminosilane-treated substrate; (<b>c</b>) immobilization of the nanotubes onto a substrate; and (<b>d</b>) binding of GO<sub>x</sub> to the nanotubes. Reprinted with permission from [<a href="#B154-polymers-09-00150" class="html-bibr">154</a>]. Copyright 2008, American Chemical Society.</p> Full article ">
1338 KiB  
Communication
Anti-Microbial Biopolymer Hydrogel Scaffolds for Stem Cell Encapsulation
by Philipp T. Kühn, René T. Rozenbaum, Estelle Perrels, Prashant K. Sharma and Patrick Van Rijn
Polymers 2017, 9(4), 149; https://doi.org/10.3390/polym9040149 - 22 Apr 2017
Cited by 11 | Viewed by 7012
Abstract
Biopolymer hydrogels are an attractive class of materials for wound dressings and other biomedical applications because of their ease of use and availability from biomass. Here, we present a hydrogel formation approach based on alginate and chitosan. Alginate is conventionally cross-linked using multivalent [...] Read more.
Biopolymer hydrogels are an attractive class of materials for wound dressings and other biomedical applications because of their ease of use and availability from biomass. Here, we present a hydrogel formation approach based on alginate and chitosan. Alginate is conventionally cross-linked using multivalent ions such as Ca2+ but in principle any polycationic species can be used such as polyelectrolytes. Exchanging the cross-linking Ca2+ ions partially with chitosan, which at pH 7 has available positive charges as well as good interactions with Ca2+, leads to an improved Young’s modulus. This gel is non-toxic to mammalian cells and hence allows conveniently for stem cell encapsulation since it is based on two-component mixing and gel formation. Additionally, the chitosan is known to have a bactericidal effect which is retained when using it in the alginate–chitosan gel formation and the formed hydrogels displayed bactericidal effects against P. aeruginosa and S. aureus. The combination of anti-bacterial properties, inclusion of stem cells, and the hydrogel nature would provide an ideal environment for complex wound healing. Full article
(This article belongs to the Special Issue Polymers and Block Copolymers at Interfaces and Surfaces)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>On the left a graph displaying the Young’s modulus dependent on the chitosan charge ratio (<b>a</b>); the line is added to guide the eye. Each point is an average of three measurements. On the right, representative AFM pictures of gels with a chitosan charge ratio of 0.0 (<b>b</b>), 0.2 (<b>c</b>), 0.4 (<b>d</b>), and 0.6 (<b>e</b>) are shown.</p> Full article ">Figure 2
<p>Results of the cell encapsulation experiments and cytotoxicity assessment of the gels. Cell concentration given in cells/mm<sup>3</sup> of gels composed of alginate and different charge ratios of chitosan to Ca<sup>2+</sup> for 1 and 5 days of culture (<b>a</b>). The percentage of living cells counted from confocal microscopy images for the same gels compared for 1 and 5 days (<b>b</b>). Representative images of encapsulated cells can be found in the <a href="#app1-polymers-09-00149" class="html-app">Supplementary Materials (Figure S3)</a>. Results of the XTT assay of hBM-MSCs cultured together with gels of different compositions for 1 and 5 days (<b>c</b>). An asterisk indicates statistical significance (<span class="html-italic">p</span> ≤ 0.05).</p> Full article ">Figure 3
<p>Bactericidal experiments of chitosan containing hydrogels. Gels with a different positive charge ratio of chitosan and Ca<sup>2+</sup> were tested using two different methods. Representative pictures of <span class="html-italic">S. aureus</span> and <span class="html-italic">P. aeruginosa</span> adhered on glass and treated with chitosan containing hydrogels are shown together with a corresponding ratio of dead and alive bacterial cells. Red indicates the amount of dead bacteria while green represents alive bacteria. Light colors show results for direct mixing (wound filling model) and dark colors for the pre-formed gels (wound dressing model). Representative pictures of bacteria can be found in the <a href="#app1-polymers-09-00149" class="html-app">Supplementary Materials (Figures S3 and S4)</a>.</p> Full article ">
18465 KiB  
Article
Effect of Cyclic Loading on Surface Instability of Silicone Rubber under Compression
by Zhonglin Li, Zhiheng Zhou, Ying Li and Shan Tang
Polymers 2017, 9(4), 148; https://doi.org/10.3390/polym9040148 - 21 Apr 2017
Cited by 19 | Viewed by 8188
Abstract
This work combines experiments and finite element simulations to study the effect of pre-imposed cyclic loading on surface instability of silicon rubber under compression. We first fabricate cuboid blocks of silicon rubber and pinch them cyclicly a few times. Then, an in-house apparatus [...] Read more.
This work combines experiments and finite element simulations to study the effect of pre-imposed cyclic loading on surface instability of silicon rubber under compression. We first fabricate cuboid blocks of silicon rubber and pinch them cyclicly a few times. Then, an in-house apparatus is set to apply uniaxial compression on the silicon rubber under exact plane strain conditions. Surprisingly, we find multiple creases on the surface of silicone rubber, significantly different from what have been observed on the samples without the cyclic pinching. To reveal the underlying physics for these experimentally observed multiple creases, we perform detailed nanoindentation experiments to measure the material properties at different locations of the silicon rubber. The modulus is found to be nonuniform and varies along the thickness direction after the cyclic pinching. According to these experimental results, three-layer and multilayer finite element models are built with different materials properties informed by experiments. The three-layer finite element model can excellently explain the nucleation and pattern of multiple surface creases on the surface of compressed silicone rubber, in good agreement with experiments. Counterintuitively, the multilayer model with gradient modulus cannot be used to explain the multiple creases observed in our experiments. According to these simulations, the experimentally observed multiple creases should be attributed to a thin and stiff layer formed on the surface of silicon rubber after the pre-imposed cyclic loading. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
►▼ Show Figures

Figure 1

Figure 1
<p>(<b>a</b>) in-house loading apparatus to realize the exact plane strain condition under uniaxial compression; (<b>b</b>) schematic of the monotonic uniaxial compression. The size of the specimen is denoted by length <span class="html-italic">L</span>, height <span class="html-italic">H</span> and width <span class="html-italic">W</span>.</p> Full article ">Figure 2
<p>(<b>a</b>) cyclic pinching on a cuboid silicone rubber; (<b>b</b>) schematic of the cyclic pinching. The loading-unloading is controlled by the imposed displacement.</p> Full article ">Figure 3
<p>Creasing pattern for a cuboid silicone rubber under the uniaxial compression and plane strain conditions. (<b>a</b>) a single crease at engineering compressive strain <math display="inline"> <semantics> <mrow> <mn>36</mn> <mo>.</mo> <mn>5</mn> <mo>%</mo> </mrow> </semantics> </math>; (<b>b</b>) double creases at engineering strain <math display="inline"> <semantics> <mrow> <mn>37</mn> <mo>.</mo> <mn>2</mn> <mo>%</mo> </mrow> </semantics> </math>. The silicone rubber does not experience cyclic loadings before the uniaxial compression.</p> Full article ">Figure 4
<p>Surface morphology of a cuboid silicone rubber under different levels of compressive strains: (<b>a</b>) <math display="inline"> <semantics> <mrow> <mn>18</mn> <mo>.</mo> <mn>1</mn> <mo>%</mo> </mrow> </semantics> </math>; (<b>b</b>) <math display="inline"> <semantics> <mrow> <mn>28</mn> <mo>.</mo> <mn>3</mn> <mo>%</mo> </mrow> </semantics> </math>; (<b>c</b>) <math display="inline"> <semantics> <mrow> <mn>30</mn> <mo>.</mo> <mn>6</mn> <mo>%</mo> </mrow> </semantics> </math>; (<b>d</b>) <math display="inline"> <semantics> <mrow> <mn>38</mn> <mo>.</mo> <mn>8</mn> <mo>%</mo> </mrow> </semantics> </math>. The specimens experience cyclic loadings before the uniaxial compression.</p> Full article ">Figure 5
<p>Surface morphology of a cuboid silicone rubber (Ecoflex 00-20 from Smooth-on Inc., Pennsylvania, PA, USA) under different levels of compressive strains: (<b>a</b>) <math display="inline"> <semantics> <mrow> <mn>20</mn> <mo>%</mo> </mrow> </semantics> </math>; (<b>b</b>) <math display="inline"> <semantics> <mrow> <mn>27</mn> <mo>%</mo> </mrow> </semantics> </math>; (<b>c</b>) <math display="inline"> <semantics> <mrow> <mn>31</mn> <mo>%</mo> </mrow> </semantics> </math>; (<b>d</b>) <math display="inline"> <semantics> <mrow> <mn>36</mn> <mo>%</mo> </mrow> </semantics> </math>. The specimen experiences cyclic pinching before the uniaxial compression.</p> Full article ">Figure 6
<p>(<b>a</b>) schematic of nanoindention test; (<b>b</b>) measured load vs. (<b>c</b>) indentation depth at the different locations on the cuboid silicone rubber along height direction. Different locations are marked as ‘A’, ‘B’, and ‘C’ on the specimen shown in the insert.</p> Full article ">Figure 7
<p>(<b>a</b>) schematic for the three-layer finite element model. The height for each layer is <math display="inline"> <semantics> <msub> <mi>h</mi> <mn>1</mn> </msub> </semantics> </math>, <math display="inline"> <semantics> <msub> <mi>h</mi> <mn>2</mn> </msub> </semantics> </math>, and <math display="inline"> <semantics> <msub> <mi>h</mi> <mn>3</mn> </msub> </semantics> </math> with modulus <math display="inline"> <semantics> <msub> <mi>E</mi> <mn>0</mn> </msub> </semantics> </math>, <math display="inline"> <semantics> <msub> <mi>E</mi> <mn>1</mn> </msub> </semantics> </math> and <math display="inline"> <semantics> <msub> <mi>E</mi> <mn>2</mn> </msub> </semantics> </math>, respectively; (<b>b</b>) schematic for a multi-layer finite element model with <math display="inline"> <semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>200</mn> </mrow> </semantics> </math> layers. The height of the <span class="html-italic">i</span>th layer is <math display="inline"> <semantics> <msub> <mi>h</mi> <mi>i</mi> </msub> </semantics> </math> with modulus <math display="inline"> <semantics> <msub> <mi>E</mi> <mi>i</mi> </msub> </semantics> </math>. The height of each layer (<math display="inline"> <semantics> <msub> <mi>h</mi> <mi>i</mi> </msub> </semantics> </math>) is equally distributed in the simulations; (<b>c</b>) the normalized modulus vs. height for the multilayer model based on linear interpolation, parabola interpolation and exponential fitting. The elastic modulus is normalized by <math display="inline"> <semantics> <msub> <mi>E</mi> <mn>0</mn> </msub> </semantics> </math>.</p> Full article ">Figure 8
<p>Buckling modes for three-layer models with different heights of each layers. (<b>a</b>) case I <math display="inline"> <semantics> <msub> <mi>h</mi> <mn>0</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <msub> <mi>h</mi> <mn>1</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <mrow> <msub> <mi>h</mi> <mn>2</mn> </msub> <mo>=</mo> <mi>H</mi> </mrow> </semantics> </math>/3:<span class="html-italic">H</span>/3:<span class="html-italic">H</span>/3; (<b>b</b>) case II <math display="inline"> <semantics> <msub> <mi>h</mi> <mn>0</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <msub> <mi>h</mi> <mn>1</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <mrow> <msub> <mi>h</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>9</mn> <mo>.</mo> <mn>5</mn> <mi>H</mi> </mrow> </semantics> </math>/20:<math display="inline"> <semantics> <mrow> <mn>9</mn> <mo>.</mo> <mn>5</mn> <mi>H</mi> </mrow> </semantics> </math>/20:<math display="inline"> <semantics> <mrow> <mi>H</mi> <mo>/</mo> <mn>20</mn> </mrow> </semantics> </math>; (<b>c</b>) case III <math display="inline"> <semantics> <msub> <mi>h</mi> <mn>0</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <msub> <mi>h</mi> <mn>1</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <mrow> <msub> <mi>h</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>49</mn> <mo>.</mo> <mn>5</mn> <mi>H</mi> </mrow> </semantics> </math>/100:<math display="inline"> <semantics> <mrow> <mn>49</mn> <mo>.</mo> <mn>5</mn> <mi>H</mi> </mrow> </semantics> </math>/100:<span class="html-italic">H</span>/100.</p> Full article ">Figure 9
<p>Evolution of surface morphology for a three-layer model at three different levels of compressive strain. (<b>a</b>) case I <math display="inline"> <semantics> <msub> <mi>h</mi> <mn>0</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <msub> <mi>h</mi> <mn>1</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <mrow> <msub> <mi>h</mi> <mn>2</mn> </msub> <mo>=</mo> <mi>H</mi> <mo>/</mo> <mn>3</mn> </mrow> </semantics> </math>:<math display="inline"> <semantics> <mrow> <mi>H</mi> <mo>/</mo> <mn>3</mn> </mrow> </semantics> </math>:<math display="inline"> <semantics> <mrow> <mi>H</mi> <mo>/</mo> <mn>3</mn> </mrow> </semantics> </math>; (<b>b</b>) case II <math display="inline"> <semantics> <msub> <mi>h</mi> <mn>0</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <msub> <mi>h</mi> <mn>1</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <mrow> <msub> <mi>h</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>9</mn> <mo>.</mo> <mn>5</mn> <mi>H</mi> <mo>/</mo> <mn>20</mn> </mrow> </semantics> </math>:<math display="inline"> <semantics> <mrow> <mn>9</mn> <mo>.</mo> <mn>5</mn> <mi>H</mi> <mo>/</mo> <mn>20</mn> </mrow> </semantics> </math>:<math display="inline"> <semantics> <mrow> <mi>H</mi> <mo>/</mo> <mn>20</mn> </mrow> </semantics> </math>; (<b>c</b>) case III <math display="inline"> <semantics> <msub> <mi>h</mi> <mn>0</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <msub> <mi>h</mi> <mn>1</mn> </msub> </semantics> </math>:<math display="inline"> <semantics> <mrow> <msub> <mi>h</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>49</mn> <mo>.</mo> <mn>5</mn> <mi>H</mi> <mo>/</mo> <mn>100</mn> </mrow> </semantics> </math>:<math display="inline"> <semantics> <mrow> <mn>49</mn> <mo>.</mo> <mn>5</mn> <mi>H</mi> <mo>/</mo> <mn>100</mn> </mrow> </semantics> </math>:<math display="inline"> <semantics> <mrow> <mi>H</mi> <mo>/</mo> <mn>100</mn> </mrow> </semantics> </math>.</p> Full article ">Figure 10
<p>Evolution of surface morphology for a three-layer model at three levels of strains with different imposed strain rates. (<b>a</b>) <math display="inline"> <semantics> <mrow> <mn>2</mn> <mo>.</mo> <mn>5</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>5</mn> </mrow> </msup> </mrow> </semantics> </math>/s; (<b>b</b>) <math display="inline"> <semantics> <mrow> <mn>2</mn> <mo>.</mo> <mn>5</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics> </math>/s; (<b>c</b>) <math display="inline"> <semantics> <mrow> <mn>2</mn> <mo>.</mo> <mn>5</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </semantics> </math>/s.</p> Full article ">Figure 11
<p>Evolution of surface morphology for multi-layer model at three levels of strains with different fitting methods for gradient modulus. (<b>a</b>) linear interpolation; (<b>b</b>) parabola interpolation; (<b>c</b>) exponential fitting.</p> Full article ">
3757 KiB  
Article
Coumarin- and Carboxyl-Functionalized Supramolecular Polybenzoxazines Form Miscible Blends with Polyvinylpyrrolidone
by Ruey-Chorng Lin, Mohamed Gamal Mohamed, Tao Chen and Shiao-Wei Kuo
Polymers 2017, 9(4), 146; https://doi.org/10.3390/polym9040146 - 21 Apr 2017
Cited by 21 | Viewed by 7959
Abstract
In this study, we synthesized a novel multifunctional benzoxazine monomer (Coumarin-COOH BZ), possessing both coumarin and COOH groups, through the reaction of 4-methyl-7-hydroxycoumarin, 4-aminobenzoic acid, and paraformaldehyde in 1,4-dioxane, with the structure confirmed using 1H and 13C nuclear magnetic resonance and [...] Read more.
In this study, we synthesized a novel multifunctional benzoxazine monomer (Coumarin-COOH BZ), possessing both coumarin and COOH groups, through the reaction of 4-methyl-7-hydroxycoumarin, 4-aminobenzoic acid, and paraformaldehyde in 1,4-dioxane, with the structure confirmed using 1H and 13C nuclear magnetic resonance and Fourier transform infrared (FTIR) spectroscopy. Differential scanning calorimetry (DSC), FTIR spectroscopy, and thermogravimetric analysis were then employed to monitor the thermal curing behavior of Coumarin-COOH BZ and its blends with poly(N-vinyl-2-pyrrolidone) (PVP), both before and after photodimerization of the coumarin moieties. DSC revealed a single glass transition temperature for each Coumarin-COOH BZ/PVP blend composition; a large positive deviation based on the Kwei equation suggested that strong hydrogen bonding existed between the Coumarin-COOH BZ and PVP segments, confirmed through FTIR spectroscopic analyses. The thermal properties improved (i.e., increased glass transition and thermal degradation temperatures) as a result of the increased crosslinking density after photodimerization under UV exposure. Full article
(This article belongs to the Special Issue Polymer Blends 2017)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) <sup>1</sup>H; and (<b>b</b>) <sup>13</sup>C NMR spectra of Coumarin-COOH BZ.</p> Full article ">Figure 2
<p>FTIR spectra of: (<b>a</b>) Coumarin-OH; (<b>b</b>) 4-aminobenzoic acid; and (<b>c</b>) Coumarin-COOH BZ.</p> Full article ">Figure 3
<p>DSC thermograms of Coumarin-COOH BZ: (<b>a</b>) uncured monomer; and (<b>b</b>–<b>e</b>) after thermal curing at: (<b>b</b>) 150; (<b>c</b>) 180; (<b>d</b>) 210; and (<b>e</b>) 240 °C, recorded after each curing stage.</p> Full article ">Figure 4
<p>FTIR spectra of Coumarin-COOH BZ: (<b>a</b>) uncured monomer; and (<b>b</b>–<b>e</b>) after thermal curing at: (<b>b</b>) 150; (<b>c</b>) 180; (<b>d</b>) 210; and (<b>e</b>) 240 °C, recorded after each curing stage.</p> Full article ">Figure 5
<p>TGA analyses of Coumarin-COOH BZ, recorded after each curing stage.</p> Full article ">Figure 6
<p>(<b>A</b>) DSC thermograms; and (<b>B</b>) FTIR spectra of Coumarin-COOH BZ/PVP blends before thermal curing: (<b>a</b>) 100/0; (<b>b</b>) 80/20; (<b>c</b>) 60/40; (<b>d</b>) 50/50; (<b>e</b>) 40/60; (<b>f</b>) 20/80; and (<b>g</b>) 0/100.</p> Full article ">Figure 7
<p>FTIR spectra of the Coumarin-COOH BZ/PVP = 50/50 blend: (<b>a</b>) uncured monomer; and (<b>b</b>–<b>e</b>) after thermal curing at: (<b>b</b>) 150; (<b>c</b>) 180; (<b>d</b>) 210; and (<b>e</b>) 240 °C, recorded after each curing stage.</p> Full article ">Figure 8
<p>DSC thermograms of poly(Coumarin-COOH BZ)/PVP blends: (<b>a</b>) 100/0; (<b>b</b>) 80/20; (<b>c</b>) 60/40; (<b>d</b>) 50/50; (<b>e</b>) 40/60; (<b>f</b>) 20/80; and (<b>g</b>) 0/100.</p> Full article ">Figure 9
<p>Glass transition temperature/composition curves, based on the Kwei equation, for poly(Coumarin-COOH BZ)/PVP blends.</p> Full article ">Figure 10
<p>FTIR spectra (1550–1800 cm<sup>−1</sup>), recorded at room temperature, for poly(Coumarin-COOH) BZ/PVP blends: (<b>a</b>) 100/0; (<b>b</b>) 80/20; (<b>c</b>) 60/40; (<b>d</b>) 50/50; (<b>e</b>) 40/60; (<b>f</b>) 20/80; and (<b>g</b>) 0/100.</p> Full article ">Figure 11
<p>(<b>A</b>) DSC thermograms; and (<b>B</b>) FTIR spectra of Coumarin-COOH BZ: (<b>a</b>) uncured monomer; (<b>b</b>) after irradiation at 365 nm; and (<b>c</b>–<b>e</b>) after irradiation at 365 nm and thermal curing at: (<b>c</b>) 150; (<b>d</b>) 180; and (<b>e</b>) 210 °C, recorded after each curing stage.</p> Full article ">Figure 12
<p>(<b>A</b>) DSC thermograms; and (<b>B</b>) FTIR spectra of the Coumarin-COOH BZ/PVP = 50/50 blend: (<b>a</b>) uncured monomer; (<b>b</b>) after irradiation at 365 nm; and (<b>c</b>–<b>e</b>) after irradiation at 365 nm and thermal curing at: (<b>c</b>) 150; (<b>d</b>) 180; and (<b>e</b>) 210 °C, recorded after each curing stage.</p> Full article ">Figure 13
<p>TGA analyses of the Coumarin-COOH BZ/PVP = 50/50 blend: (<b>a</b>) uncured monomer; (<b>b</b>) after thermal curing; and (<b>c</b>) after irradiation at 365 nm and thermal curing.</p> Full article ">Scheme 1
<p>Chemical structures of: (<b>a</b>) Coumarin-OH; (<b>b</b>) Coumarin-COOH BZ; and (<b>c</b>) poly(Coumarin-COOH BZ).</p> Full article ">Scheme 2
<p>Photodimerization of Coumarin-COOH BZ with subsequent thermal curing to form PBZ matrices of high crosslinking density.</p> Full article ">
2140 KiB  
Article
Synthesis, Characterization and Thermal Properties of Poly(ethylene oxide), PEO, Polymacromonomers via Anionic and Ring Opening Metathesis Polymerization
by George V. Theodosopoulos, Christos Zisis, Georgios Charalambidis, Vasilis Nikolaou, Athanassios G. Coutsolelos and Marinos Pitsikalis
Polymers 2017, 9(4), 145; https://doi.org/10.3390/polym9040145 - 21 Apr 2017
Cited by 34 | Viewed by 8347
Abstract
Branched polymers are a valuable class of polymeric materials. In the present study, anionic polymerization techniques were employed for the synthesis of low molecular weight poly(ethylene oxide) (PEO) macromonomers bearing norbornenyl end groups. The macromonomers were characterized by SEC, MALDI-TOF and NMR spectroscopy. [...] Read more.
Branched polymers are a valuable class of polymeric materials. In the present study, anionic polymerization techniques were employed for the synthesis of low molecular weight poly(ethylene oxide) (PEO) macromonomers bearing norbornenyl end groups. The macromonomers were characterized by SEC, MALDI-TOF and NMR spectroscopy. Subsequent ring opening metathesis polymerization (ROMP) of the macromonomers using ruthenium catalysts (Grubbs catalysts of the 1st, 2nd and 3rd generations) afforded the corresponding polymacromonomers. The effects of the macromonomer molecular weight, the type of the catalyst, the nature of the solvent, the monomer concentration and the polymerization temperature on the molecular characteristics of the branched polymers were examined in detail. The crystallization behavior of the macromonomers and the corresponding polymacromonomers were studied by Differential Scanning Calorimetry (DSC). The thermal stability and the kinetics of the thermal decomposition of the samples were also studied by Thermogravimetric Analysis (TGA). The activation energies of the thermal decomposition were analyzed using the Ozawa–Flynn–Wall and Kissinger methodologies. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p><sup>1</sup>H-NMR spectrum of PEO 1k macromonomer in CDCl<sub>3</sub>.</p> Full article ">Figure 2
<p>MALDI TOF-MS spectrum of PEO 1k macromonomer.</p> Full article ">Figure 3
<p>SEC traces of PEO 1k macromonomer and polymacromonomer having <span class="html-italic">M</span><sub>w</sub> = 25,000, <span class="html-italic">M</span><sub>w</sub>/<span class="html-italic">M</span><sub>n</sub> = 1.18).</p> Full article ">Figure 4
<p>Derivative weight loss with temperature for PEO 1k under different heating rates.</p> Full article ">Figure 5
<p>Derivative weight loss with temperature for 1-205-3-THF under different heating rates.</p> Full article ">Figure 6
<p>OFW (Ozawa–Flynn–Wall) plots for 3-50-3-THF.</p> Full article ">Figure 7
<p>Kissinger plot for 3-50-3-THF.</p> Full article ">Scheme 1
<p>Synthetic route for the preparation of the norbornenyl oxyanion initiator.</p> Full article ">Scheme 2
<p>Polymerization of ethylene oxide with the norbornenyl oxyanion initiator and two different terminating agents.</p> Full article ">Scheme 3
<p>Synthesis of PEO polymacromonomers.</p> Full article ">
6746 KiB  
Article
Morphology Control of Ni(II)-NTA-End-Functionalized Block Copolymer and Bio-Conjugation through Metal-Ligand Complex
by Dasom Park, Chaeyeon Lee, Minsu Chae, Mohammad Abdul Kadir, Ji Eun Choi, Jae Kwang Song and Hyun-jong Paik
Polymers 2017, 9(4), 144; https://doi.org/10.3390/polym9040144 - 20 Apr 2017
Cited by 2 | Viewed by 6895
Abstract
This study demonstrates the synthesis of an amphiphilic block copolymer, Ni2+-nitrilotiracetic acid-end-functionalized-poly(poly(ethylene glycol)methyl ether methacrylate)-block-polystyrene (NTA-p(PEGMA-b-St)), morphology control via their self-assembly behavior and reversible bioconjugation of hexahistidine-tagged green fluorescent protein (His6-GFP) onto the [...] Read more.
This study demonstrates the synthesis of an amphiphilic block copolymer, Ni2+-nitrilotiracetic acid-end-functionalized-poly(poly(ethylene glycol)methyl ether methacrylate)-block-polystyrene (NTA-p(PEGMA-b-St)), morphology control via their self-assembly behavior and reversible bioconjugation of hexahistidine-tagged green fluorescent protein (His6-GFP) onto the surfaces of polymeric vesicles through nitrilotriacetic acid (NTA)-Ni2+-His interaction. First, the t-boc-protected-NTA-p(PEGMA-b-St) was synthesized by atom transfer radical polymerization. After the removal of the t-boc protecting group, the NTA group of the polymer was complexed with Ni2+. To induce self-assembly, water was added as a selective solvent to the solution of the copolymer in tetrahydrofuran (THF). Varying the water content of the solution resulted in various morphologies including spheres, lamellas and vesicles. Finally, polymeric vesicles decorated with green fluorescent protein (GFP) on their surfaces were prepared by the addition of His6-GFP into the vesicles solution. Reversibility of the binding between vesicles and His6-GFP was confirmed with a fluorescent microscope. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Size exclusion chromatography (SEC) traces of polymers. Solid line for <span class="html-italic">t</span>-<span class="html-italic">boc</span>-NTA-<span class="html-italic">p</span>(PEGMA) (<b>2</b>); dash line for <span class="html-italic">t</span>-<span class="html-italic">boc</span>-NTA-<span class="html-italic">p</span>(PEGMA-<span class="html-italic">b</span>-St) (<b>3</b>).</p> Full article ">Figure 2
<p><sup>1</sup>H NMR (500 MHz) spectrum of <span class="html-italic">t</span>-<span class="html-italic">boc</span>-NTA-<span class="html-italic">p</span>(PEGMA) (<b>2</b>) in, CDCl<sub>3</sub>.</p> Full article ">Figure 3
<p><sup>1</sup>H NMR (500 MHz) spectrum of <span class="html-italic">t</span>-<span class="html-italic">boc</span>-NTA-<span class="html-italic">p</span>(PEGMA-<span class="html-italic">b</span>-St) (<b>3</b>) and NTA-<span class="html-italic">p</span>(PEGMA-<span class="html-italic">b</span>-St) (<b>4</b>) in CDCl<sub>3</sub>.</p> Full article ">Figure 4
<p>Morphology observation through dynamic light scattering (DLS) and transmission electron microscope (TEM) measurement of 0.1 wt % of <span class="html-italic">t</span>-<span class="html-italic">boc</span>-NTA-<span class="html-italic">p</span>(PEGMA-<span class="html-italic">b</span>-St)/Ni<sup>2+</sup>-NTA-<span class="html-italic">p</span>(PEGMA-<span class="html-italic">b</span>-St) according to water concentration; (<b>a</b>) spherical micelles at 8.68 wt % water; (<b>b</b>) morphology transition at from 9.74 wt % to 11.93 wt % water morphology transition for 9.74–11.93 wt % water; (<b>c</b>) vesicles at 14.25 wt % water.</p> Full article ">Figure 5
<p>Preparation of bio conjugate between hexahistidine-tagged green fluorescent protein (His<sub>6</sub>-GFP) and polymeric vesicles and release of His<sub>6</sub>-GFP from the GFP-polymeric vesicles conjugate. TEM, optical and fluorescence microscope images of before His<sub>6</sub>-GFP addition (<b>a</b>), after His<sub>6</sub>-GFP addition to vesicle solution (<b>b</b>) and after imidazole addition to GFP-vesicle solution (<b>c</b>).</p> Full article ">Scheme 1
<p>Morphology transition of Ni<sup>2+</sup>-nitrilotriacetic acid (NTA)-end-functionalized block copolymer and protein conjugation.</p> Full article ">Scheme 2
<p>Synthesis of Ni<sup>2+</sup>-nitrilotiracetic acid-end-functionalized-poly(poly(ethylene glycol)methyl ether methacrylate)-<span class="html-italic">block</span>-polystyrene (NTA-<span class="html-italic">p</span>(PEGMA-<span class="html-italic">b</span>-St)).</p> Full article ">
19218 KiB  
Article
Simple Synthesis of Hydroxyl and Ethylene Functionalized Aromatic Polyamides as Sizing Agents to Improve Adhesion Properties of Aramid Fiber/Vinyl Epoxy Composites
by Minglin Qin, Haijuan Kong, Kang Zhang, Cuiqing Teng, Muhuo Yu and Yaozu Liao
Polymers 2017, 9(4), 143; https://doi.org/10.3390/polym9040143 - 20 Apr 2017
Cited by 14 | Viewed by 7199
Abstract
To improve interfacial adhesion between aramid fibers and vinyl epoxy resins, a series of hydroxyl and ethylene-functional aromatic polyamides ((ClPPTA)m-R′) with different chain segments were successfully synthesized via a one-pot low-temperature polycondensation. The hydroxyl and ethylene-functional aromatic polyamides were characterized by [...] Read more.
To improve interfacial adhesion between aramid fibers and vinyl epoxy resins, a series of hydroxyl and ethylene-functional aromatic polyamides ((ClPPTA)m-R′) with different chain segments were successfully synthesized via a one-pot low-temperature polycondensation. The hydroxyl and ethylene-functional aromatic polyamides were characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state 13C CP/MAS nuclear magnetic resonance spectroscopy (13C CP/MAS NMR), thermal gravimetric analysis (TGA), and wide-angle X-ray diffraction (WXRD). The contact angle of the hydroxyl and ethylene-functional aromatic polyamides films were measured. The hydroxyl and ethylene-functional aromatic polyamides were used as the sizing agents for aramid fiber/vinyl epoxy composites. The surface chemical composition and morphology of the unsized and sized fibers were identified using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The interfacial adhesion between aramid fibers and vinyl epoxy composites was investigated by the micro-debond tests. The results showed that the interfacial shear strength between the sized aramid fibers and vinyl epoxy composites was greatly improved. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>FT-IR spectra of the Poly(<span class="html-italic">p</span>-phenylene terphthalamide) (PPTA) and ((ClPPTA)<sub>m</sub>-R′) in the wavenumber range of (<b>a</b>) 600–4000 cm<sup>−1</sup>, (<b>b</b>) 1400–1600 cm<sup>−1</sup> and (<b>c</b>) 3500–3200 cm<sup>−1</sup>.</p> Full article ">Figure 2
<p>Solid state CP/MAS <sup>13</sup>C NMR spectra of the PPTA and the hydroxyl and ethylene-functional aromatic polyamides.</p> Full article ">Figure 3
<p>X-ray powder diffraction of the PPTA and hydroxyl and ethylene-functional aromatic polyamides, respectively.</p> Full article ">Figure 4
<p>TGA curves of the hydroxyl and ethylene-functional aromatic polyamides, respectively.</p> Full article ">Figure 5
<p>PPTA films (<b>a</b>) and static contact angle tests of the hydroxyl and ethylene-functional aromatic polyamides i.e., ((ClPPTA)<sub>m</sub>-R′) films (<b>b</b>–<b>f</b>).</p> Full article ">Figure 6
<p>C 1s spectra of unsized (<b>a</b>) and sized (<b>b</b>) aramid fibers.</p> Full article ">Figure 7
<p>SEM images of (<b>a</b>) unsized aramid fiber (AF) and (<b>b</b>–<b>f</b>) the sized ones: (<b>b</b>) AF-(ClPPTA)<sub>2</sub>-R′-1.5%; (<b>c</b>) AF-(ClPPTA)<sub>4</sub>-R′-1.5%; (<b>d</b>) AF-(ClPPTA)<sub>6</sub>-R′-1.5%; (<b>e</b>) AF-(ClPPTA)<sub>8</sub>-R′-1.5%; and (<b>f</b>) AF-(ClPPTA)<sub>10</sub>-R′-1.5%.</p> Full article ">Figure 8
<p>Influence of molecular weight and concentration of ((ClPPTA)<sub>m</sub>-R′) on the IFSS properties of aramid fibers and vinyl epoxy composites: (<b>a</b>–<b>e</b>) in different solid content of ((ClPPTA)<sub>m</sub>-R′) (1.0–2.0%) dissolved in NMP/LiCl as the sizing agents of aramid fibers to impact on the IFSS of vinyl epoxy composites; (<b>f</b>) the same of solid content of ((ClPPTA)<sub>m</sub>-R′) (1.5%) dissolved in NMP/LiCl as the sizing agents of aramid fibers to impact on the IFSS of vinyl epoxy composites</p> Full article ">Figure 9
<p>The proposed possible mechanism of the reaction between sized of aramid fibers and vinyl epoxy resin.</p> Full article ">Scheme 1
<p>Synthetic route of the hydroxyl and ethylene-functional aromatic polyamides i.e., ((ClPPTA)<sub>m</sub>-R′).</p> Full article ">Scheme 2
<p>Possible mechanism of ring-forming reaction in hydroxyl and ethylene-functional aromatic polyamides i.e., ((ClPPTA)<sub>m</sub>-R′).</p> Full article ">
2680 KiB  
Article
Influence of Defined Hydrophilic Blocks within Oligoaminoamide Copolymers: Compaction versus Shielding of pDNA Nanoparticles
by Stephan Morys, Ana Krhac Levacic, Sarah Urnauer, Susanne Kempter, Sarah Kern, Joachim O. Rädler, Christine Spitzweg, Ulrich Lächelt and Ernst Wagner
Polymers 2017, 9(4), 142; https://doi.org/10.3390/polym9040142 - 19 Apr 2017
Cited by 17 | Viewed by 6932
Abstract
Cationic polymers are promising components of the versatile platform of non-viral nucleic acid (NA) delivery agents. For a successful gene delivery system, these NA vehicles need to comprise several functionalities. This work focuses on the modification of oligoaminoamide carriers with hydrophilic oligomer blocks [...] Read more.
Cationic polymers are promising components of the versatile platform of non-viral nucleic acid (NA) delivery agents. For a successful gene delivery system, these NA vehicles need to comprise several functionalities. This work focuses on the modification of oligoaminoamide carriers with hydrophilic oligomer blocks mediating nanoparticle shielding potential, which is necessary to prevent aggregation or dissociation of NA polyplexes in vitro, and hinder opsonization with blood components in vivo. Herein, the shielding agent polyethylene glycol (PEG) in three defined lengths (12, 24, or 48 oxyethylene repeats) is compared with two peptidic shielding blocks composed of four or eight repeats of sequential proline-alanine-serine (PAS). With both types of shielding agents, we found opposing effects of the length of hydrophilic segments on shielding and compaction of formed plasmid DNA (pDNA) nanoparticles. Two-arm oligoaminoamides with 37 cationizable nitrogens linked to 12 oxyethylene units or four PAS repeats resulted in very compact 40–50 nm pDNA nanoparticles, whereas longer shielding molecules destabilize the investigated polyplexes. Thus, the balance between sufficiently shielded but still compact and stable particles can be considered a critical optimization parameter for non-viral nucleic acid vehicles based on hydrophilic-cationic block oligomers. Full article
(This article belongs to the Special Issue Polymers and Nanogels for Gene Therapy)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>A</b>) Stability testing of untargeted polyplexes against phosphate-buffered saline (PBS). After 30 min of polyplex incubation (2 µg pDNA; N/P 12) in deionized water and addition of 500 µL PBS, DLS measurement was performed. Time points 0, 5, 30, 60, and 180 min were displayed. In case of colloidally-stable polyplexes of PEG<sub>24</sub>, PEG<sub>48</sub>, and PAS<sub>8</sub>, a measurement after 24 h is also displayed. Data are presented as mean value (±SD) out of triplets; (<b>B</b>) Polyplexes (2 µg pDNA; N/P 12) were incubated in HBG with or without 3 × 10<sup>6</sup> erythrocytes. After centrifugation, the supernatant was taken, and 3500 IU of heparin were added to release pDNA of the polyplexes. Cy5 fluorescence was compared to uncomplexed (free) pDNA. Statistical analysis (Student’s <span class="html-italic">t</span>-test): ns <span class="html-italic">p</span> &gt; 0.05, * <span class="html-italic">p</span> ≤ 0.05; ** <span class="html-italic">p</span> ≤ 0.01.</p> Full article ">Figure 2
<p>(<b>A</b>) Transmission electron microscopy images of polyplexes formed at N/P 12 in deionized water and stained with uranylformate. Scale bar represents 100 nm; (<b>B</b>) <b>Left</b>: pDNA compaction, correlating with the remaining fluorescence of ethidium bromide (EtBr). Results are calculated against free pDNA. <b>Right</b>: Polyplexes at N/P 12 after addition of 250 IU of heparin. lPEI: linear polyethylenimine. Statistical analysis (Student’s <span class="html-italic">t</span>-test): ns <span class="html-italic">p</span> &gt; 0.05, * <span class="html-italic">p</span> ≤ 0.05; ** <span class="html-italic">p</span> ≤ 0.01; **** <span class="html-italic">p</span> ≤ 0.0001.</p> Full article ">Figure 3
<p>(<b>A</b>) DLS measurements of 90% fetal bovine serum (FBS, green) and pDNA polyplexes of the three-arm oligomer in HBG (red) as references to discriminate polyplex and serum peaks; (<b>B</b>–<b>G</b>) Display behavior of polyplexes with indicated oligomers in 90% FBS over time. In (<b>H</b>), the amount of recovered pDNA of polyplexes containing Cy5-labeled pDNA after treatment with 3500 IU heparin is displayed after incubation with FBS for 30 min; HBG-treated polyplexes served as control.</p> Full article ">Figure 4
<p>In (<b>A</b>,<b>B</b>) cellular association of polyplexes with N2a cells after 30 min incubation at 4 °C as determined by flow cytometry is plotted; In (<b>C</b>,<b>D</b>) cellular internalization of polyplexes after 45 min incubation at 37 °C followed by removal of extracellularly-bound polyplexes is displayed; Logarithmic X-scale in (<b>A</b>–<b>D</b>) represents Cy5 fluorescence of polyplexes; (<b>E</b>) Luciferase reporter gene expression in N2a cells after 0.75 h (without pattern) and after 24 h (with pattern). Transfections were performed at two different ratios: N/P = 6 (red) and N/P = 12 (green). (<b>F</b>) Cell viability assay was performed in parallel.</p> Full article ">Figure 5
<p>(<b>A</b>) Luciferase reporter gene expression in human prostate cancer cell line DU145 as well as in (<b>B</b>) human hepatocellular cancer cells Huh7 after 0.75 h (without pattern), and after 24 h (with pattern). Transfections were performed at two different ratios: N/P = 6 (red) and N/P = 12 (green); (<b>C</b>) Luciferase gene expression at 48 h after intratumoral administration of pCMVLuc polyplexes at N/P = 12 into Huh7 tumor-bearing mice. Luciferase gene expression is presented as relative light units per gram tumor (RLU/g tumor; <span class="html-italic">n</span> = 5, mean ± SEM). Lysis buffer RLU values were subtracted.</p> Full article ">Figure 5 Cont.
<p>(<b>A</b>) Luciferase reporter gene expression in human prostate cancer cell line DU145 as well as in (<b>B</b>) human hepatocellular cancer cells Huh7 after 0.75 h (without pattern), and after 24 h (with pattern). Transfections were performed at two different ratios: N/P = 6 (red) and N/P = 12 (green); (<b>C</b>) Luciferase gene expression at 48 h after intratumoral administration of pCMVLuc polyplexes at N/P = 12 into Huh7 tumor-bearing mice. Luciferase gene expression is presented as relative light units per gram tumor (RLU/g tumor; <span class="html-italic">n</span> = 5, mean ± SEM). Lysis buffer RLU values were subtracted.</p> Full article ">Scheme 1
<p>Schematic structures of the oligomer topologies evaluated in this paper. PAS: proline-alanine-serine; PEG: polyethylene glycol.</p> Full article ">
3351 KiB  
Article
Copolymerization of Norbornene and Norbornadiene Using a cis-Selective Bimetallic W-Based Catalytic System
by Grigorios Raptopoulos, Katerina Kyriakou, Gregor Mali, Alice Scarpellini, George C. Anyfantis, Thomas Mavromoustakos, Marinos Pitsikalis and Patrina Paraskevopoulou
Polymers 2017, 9(4), 141; https://doi.org/10.3390/polym9040141 - 18 Apr 2017
Cited by 12 | Viewed by 6872
Abstract
The bimetallic cluster Na[W2(μ-Cl)3Cl4(THF)2]·(THF)3 ({W2}, {W 3 W}6+, a′2e′4), which features a triple metal-metal bond, is a highly efficient room-temperature initiator for ring opening [...] Read more.
The bimetallic cluster Na[W2(μ-Cl)3Cl4(THF)2]·(THF)3 ({W2}, {W 3 W}6+, a′2e′4), which features a triple metal-metal bond, is a highly efficient room-temperature initiator for ring opening metathesis polymerization (ROMP) of norbornene (NBE) and norbornadiene (NBD), providing high-cis polymers. In this work, {W2} was used for the copolymerization of the aforementioned monomers, yielding statistical poly(norbornene)/poly(norbornadiene) PNBE/PNBD copolymers of high molecular weight and high-cis content. The composition of the polymer chain was estimated by 13C CPMAS NMR data and it was found that the ratio of PNBE/PNBD segments in the polymer chain was relative to the monomer molar ratio in the reaction mixture. The thermal properties of all copolymers were similar, resembled the properties of PNBD homopolymer and indicated a high degree of cross-linking. The morphology of all materials in this study was smooth and non-porous; copolymers with higher PNBE content featured a corrugated morphology. Glass transition temperatures were lower for the copolymers than for the homopolymers, providing a strong indication that those materials featured a branched-shaped structure. This conclusion was further supported by viscosity measurements of copolymers solutions in THF. The molecular structure of those materials can be controlled, potentially leading to well-defined star polymers via the “core-first” synthesis method. Therefore, {W2} is not only a cost-efficient, practical, highly active, and cis-stereoselective ROMP-initiator, but it can also be used for the synthesis of more complex macromolecular structures. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p><sup>1</sup>H-NMR spectrum of linear PNBE/PNBD 400/100 copolymer.</p> Full article ">Figure 2
<p><sup>13</sup>C CPMAS NMR spectra of PNBE obtained with catalytic systems {W<sub>2</sub>} and RuCl<sub>3</sub>/H<sub>2</sub>O, as indicated. The peak assigned to <span class="html-italic">cis</span> segments of the polymer chain is indicated with an arrow.</p> Full article ">Figure 3
<p><sup>13</sup>C CPMAS NMR spectra of PNBE and PNBD homopolymers, and PNBE/PNBD copolymers with various NBE/NBD molar ratios, as indicated. Peaks characteristic and distinct for PNBE and PNBD are indicated with arrows.</p> Full article ">Figure 4
<p>Weight loss (%) vs. temperature (°C) for all samples, as indicated.</p> Full article ">Figure 5
<p>Derivative weight loss (%/°C) vs. temperature (°C) for all samples, as indicated.</p> Full article ">Figure 6
<p>SEM images of: (<b>a</b>) PNBE homopolymer; (<b>b</b>) PNBE/PNBD 400/100 copolymer; (<b>c</b>) PNBE/PNBD 700/700 copolymer; (<b>d</b>) PNBE/PNBD 100/400 copolymer; (<b>e</b>) PNBD homopolymer.</p> Full article ">Figure 7
<p>Viscometry results of sample 2 (<a href="#polymers-09-00141-t004" class="html-table">Table 4</a>) in THF at 35 °C.</p> Full article ">Scheme 1
<p>Copolymerization of NBE and NBD via ROMP with {W<sub>2</sub>}.</p> Full article ">
1916 KiB  
Article
Artificial Spores: Immunoprotective Nanocoating of Red Blood Cells with Supramolecular Ferric Ion-Tannic Acid Complex
by Taegyun Park, Ji Yup Kim, Hyeoncheol Cho, Hee Chul Moon, Beom Jin Kim, Ji Hun Park, Daewha Hong, Joonhong Park and Insung S. Choi
Polymers 2017, 9(4), 140; https://doi.org/10.3390/polym9040140 - 13 Apr 2017
Cited by 52 | Viewed by 9748
Abstract
The blood-type-mismatch problem, in addition to shortage of blood donation, in blood transfusion has prompted the researchers to develop universal blood that does not require blood typing. In this work, the “cell-in-shell” (i.e., artificial spore) approach is utilized to shield the immune-provoking epitopes [...] Read more.
The blood-type-mismatch problem, in addition to shortage of blood donation, in blood transfusion has prompted the researchers to develop universal blood that does not require blood typing. In this work, the “cell-in-shell” (i.e., artificial spore) approach is utilized to shield the immune-provoking epitopes on the surface of red blood cells (RBCs). Individual RBCs are successfully coated with supramolecular metal-organic coordination complex of ferric ion (FeIII) and tannic acid (TA). The use of isotonic saline (0.85% NaCl) is found to be critical in the formation of stable, reasonably thick (20 nm) shells on RBCs without any aggregation and hemolysis. The formed “RBC-in-shell” structures maintain their original shapes, and effectively attenuate the antibody-mediated agglutination. Moreover, the oxygen-carrying capability of RBCs is not deteriorated after shell formation. This work suggests a simple but fast method for generating immune-camouflaged RBCs, which would contribute to the development of universal blood. Full article
(This article belongs to the Special Issue Advance of Polymers Applied to Biomedical Applications: Cell Scaffolds)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic representation for supramolecular shell formation of ferric ion (Fe<sup>III</sup>) and tannic acid (TA) on individual red blood cells (RBCs).</p> Full article ">Figure 2
<p>Characterizations of native RBC and RBC@[Fe<sup>III</sup>-TA]. (<b>a</b>) Photographs of RBC suspension and pellet before and after shell formation. (<b>b</b>) Raman spectra of (blue) native RBC and (red) RBC@[Fe<sup>III</sup>-TA]. Black arrows indicate the strong bands attributed to the ring structures of TA. (<b>c</b>) CLSM images of native RBC and RBC@[Fe<sup>III</sup>-TA] after incubation with BSA-Alexa Fluor<sup>®</sup> 647. (<b>d</b>) SEM micrographs of native RBC and RBC@[Fe<sup>III</sup>-TA]. (<b>e</b>) SEM micrographs of the membrane of native RBC and RBC@[Fe<sup>III</sup>-TA] after hypotonic lysis.</p> Full article ">Figure 3
<p>(<b>a</b>) TEM micrographs of native RBC and RBC@[Fe<sup>III</sup>-TA]. (<b>b</b>) (<b>top</b>) AFM micrographs and (<b>bottom</b>) line-profile graphs of native RBC and RBC@[Fe<sup>III</sup>-TA]. White lines in AFM micrographs indicate the path of line-profile analysis.</p> Full article ">Figure 4
<p>(<b>a</b>) Antibody-mediated agglutination assay. Native RBCs or RBC@[Fe<sup>III</sup>-TA] cells were mixed with their anti-type sera, and the optical images were taken after one hour. (<b>b</b>) Oxygen consumption graphs. The dissolved oxygen concentration (%) in PBS (pH 7.4) was plotted as a function of time. The initial oxygen concentration dissolved in the O<sub>2</sub>-purged PBS was about 39%, and the oxygen concentration was recorded by the oxygen probe connected with LabQuest<sup>®</sup>.</p> Full article ">
2669 KiB  
Article
Stereoregular Brush Polymers and Graft Copolymers by Chiral Zirconocene-Mediated Coordination Polymerization of P3HT Macromers
by Yang Wang, Travis S. Bailey, Miao Hong and Eugene Y.-X. Chen
Polymers 2017, 9(4), 139; https://doi.org/10.3390/polym9040139 - 13 Apr 2017
Cited by 8 | Viewed by 8196
Abstract
Two poly(3-hexylthiophene) (P3HT) macromers containing a donor polymer with a polymerizable methacrylate (MA) end group, P3HT-CH2-MA and P3HT-(CH2)2-MA, have been synthesized, and P3HT-(CH2)2-MA has been successfully homopolymerized and copolymerized with methyl methacrylate (MMA) [...] Read more.
Two poly(3-hexylthiophene) (P3HT) macromers containing a donor polymer with a polymerizable methacrylate (MA) end group, P3HT-CH2-MA and P3HT-(CH2)2-MA, have been synthesized, and P3HT-(CH2)2-MA has been successfully homopolymerized and copolymerized with methyl methacrylate (MMA) into stereoregular brush polymers and graft copolymers, respectively, using chiral ansa-zirconocene catalysts. Macromer P3HT-CH2-MA is too sterically hindered to polymerize by the current Zr catalysts, but macromer P3HT-(CH2)2-MA is readily polymerizable via either homopolymerization or copolymerization with MMA in a stereospecific fashion with both C2-ligated zirconocenium catalyst 1 and Cs-ligated zirconocenium catalyst 2. Thus, highly isotactic (with mm% ≥ 92%) and syndiotactic (with rr% ≥ 93%) brush polymers, it-PMA-g-P3HT and st-PMA-g-P3HT, as well as well-defined stereoregular graft copolymers with different grafted P3HT densities, it-P(M)MA-g-P3HT and st-P(M)MA-g-P3HT, have been synthesized using this controlled coordination-addition polymerization system under ambient conditions. These stereoregular brush polymers and graft copolymers exhibit both thermal (glass and melting) transitions with Tg and Tm values corresponding to transitions within the stereoregular P(M)MA and crystalline P3HT domains. Acceptor molecules such as C60 can be effectively encapsulated inside the helical cavity of st-P(M)MA-g-P3HT to form a unique supramolecular helical crystalline complex, thus offering a novel strategy to control the donor/acceptor solar cell domain morphology. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p><sup>1</sup>H-NMR (400 MHz, CDCl<sub>3</sub>) spectrum of H-P3HT-Br with <span class="html-italic">M</span><sub>w</sub> ~ 3500 g/mol.</p> Full article ">Figure 2
<p>MALDI-TOF MS spectrum showing P3HT with both H/Br (major) and Br/Br (minor) chain-ends.</p> Full article ">Figure 3
<p><sup>1</sup>H-NMR (400 MHz, CDCl<sub>3</sub>) spectrum of macromer P3HT-(CH<sub>2</sub>)<sub>2</sub>-MA.</p> Full article ">Figure 4
<p>MALDI-TOF spectrum (inset) of macromer P3HT-(CH<sub>2</sub>)<sub>2</sub>-MA (<span class="html-italic">M</span><sub>w</sub> ~ 3500 g/mol by NMR) and plot of <span class="html-italic">m</span>/<span class="html-italic">z</span> values (<span class="html-italic">y</span>-axis) vs. the number of P3HT repeat units (<span class="html-italic">x</span>-axis).</p> Full article ">Figure 5
<p><sup>1</sup>H-NMR spectrum (400 MHz, in CDCl<sub>3</sub>) of graft copolymer <span class="html-italic">it</span>-P(M)MA-<span class="html-italic">g</span>-P3HT produced by <span class="html-italic">C</span><sub>2</sub>-ligated Zr-<b>1</b> (<a href="#polymers-09-00139-t001" class="html-table">Table 1</a>, Run 3). Insets: blowup of the PMMA methyl triad region (top) and P3HT-(CH<sub>2</sub>)<sub>2</sub>-MA double bond region (7×, bottom).</p> Full article ">Figure 6
<p>GPC curves for stereoregular graft copolymers <span class="html-italic">it</span>- or <span class="html-italic">st</span>-P(M)MA-<span class="html-italic">g</span>-P3HT: black line (<a href="#polymers-09-00139-t001" class="html-table">Table 1</a>, Run 2); blue line (<a href="#polymers-09-00139-t001" class="html-table">Table 1</a>, Run 3); and green line (<a href="#polymers-09-00139-t001" class="html-table">Table 1</a>, Run 5).</p> Full article ">Figure 7
<p>DSC curves for isotactic brush homopolymer <span class="html-italic">it</span>-PMA-<span class="html-italic">g</span>-P3HT and graft copolymer <span class="html-italic">it</span>-P(M)MA-<span class="html-italic">g</span>-P3HT (4.3 mol % and 13.2 mol % P3HT) produced by the <span class="html-italic">C</span><sub>2</sub>-ligated catalyst. Curves for isotactic <span class="html-italic">it</span>-PMMA and P3HT are included for comparison.</p> Full article ">Figure 8
<p>DSC curves for graft copolymer <span class="html-italic">st</span>-P(M)MA-<span class="html-italic">g</span>-P3HT (3.9 mol % P3HT, run 5, <a href="#polymers-09-00139-t001" class="html-table">Table 1</a>) produced by the <span class="html-italic">C</span><sub>s</sub>-ligated catalyst. Curves for syndiotactic <span class="html-italic">st</span>-PMMA and P3HT are included for comparison.</p> Full article ">Figure 9
<p>DSC curves for <span class="html-italic">st</span>-P(M)MA-<span class="html-italic">g</span>-P3HT/C<sub>60</sub> complex. Curves for syndiotactic <span class="html-italic">st</span>-PMMA and P3HT are included for comparison.</p> Full article ">Scheme 1
<p>Synthetic routes to macromers P3HT-(CH<sub>2</sub>)<sub>2</sub>-MA and P3HT-CH<sub>2</sub>-MA.</p> Full article ">Scheme 2
<p>Structures of <span class="html-italic">C</span><sub>2</sub>-symmetric and <span class="html-italic">C</span><sub>s</sub>-symmetric pre-catalysts and activation reactions to the cationic catalysts.</p> Full article ">
2881 KiB  
Article
A Multiple Shape Memory Hydrogel Induced by Reversible Physical Interactions at Ambient Condition
by He Xiao, Chunxin Ma, Xiaoxia Le, Li Wang, Wei Lu, Patrick Theato, Tuoping Hu, Jiawei Zhang and Tao Chen
Polymers 2017, 9(4), 138; https://doi.org/10.3390/polym9040138 - 12 Apr 2017
Cited by 29 | Viewed by 9524
Abstract
A novel multiple shape memory hydrogel is fabricated based on two reversible physical interactions. The multiple shape memory property is endowed by a simple treatment of soaking in NaOH or NaCl solutions to form chitosan microcrystal or chain-entanglement crosslinks as temporary junctions. Full article
(This article belongs to the Special Issue Functionally Responsive Polymeric Materials)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The cross-section SEM images of (<b>a</b>) original PAAm-CS hydrogel; (<b>b</b>) PAAm-CS hydrogel soaked in NaOH (0.75 mM); (<b>c</b>) PAAm-CS Hydrogel soaked in saturated NaCl. (Scale bars, 10 μm) (<b>d</b>) Tensile stress–strain curves and (<b>e</b>) compressive stress–strain curves of different hydrogels.</p> Full article ">Figure 2
<p>(<b>a</b>) The shape memory behavior and mechanism based on chitosan physical microcrystalline crosslink. (<b>b</b>) Variation of the shape fixity ratios of the PAAm-CS hydrogels as a function of the fixity time in NaOH solution (75 mM). (<b>c</b>) Variation of the shape fixity ratios as a function of concentration of NaOH solution with a shape fixity time of 1 min. (<b>d</b>) Images of the more complex temporary shapes of PAAm-CS hydrogel fixed by NaOH (75 mM).</p> Full article ">Figure 3
<p>(<b>a</b>) The process and mechanism of the shape memory behavior with chitosan chain-entanglement as temporary crosslinks. (<b>b</b>) Variation of the shape fixity ratios of the PAAm-CS hydrogels as a function of the fixity time in saturated NaCl solution. (<b>c</b>) Variations of the shape fixity ratios as a function of concentration of NaCl solution with a shape fixity time of 1.5 min. (<b>d</b>) Images of the more complicated temporary shapes fixed by saturated NaCl solution.</p> Full article ">Figure 4
<p>The shape memory processes and mechanisms of the multiple shape memory behavior. The multiple shape memory behavior based on (<b>a</b>) the CS physical microcrystalline crosslink and (<b>b</b>) the CS chain-entanglement.</p> Full article ">Figure 5
<p>The process and mechanism of the programmable triple shape memory and recovery.</p> Full article ">Scheme 1
<p>The mechanisms of the shape memory hydrogel based on two physical interactions. Acrylamide was polymerized in the presence of chitosan. The reversible CS microcrystalline crosslinks and CS chain-entanglement endowed the hydrogel with a programmable multiple shape memory ability.</p> Full article ">
6858 KiB  
Review
pH Sensitive Hydrogels in Drug Delivery: Brief History, Properties, Swelling, and Release Mechanism, Material Selection and Applications
by Muhammad Rizwan, Rosiyah Yahya, Aziz Hassan, Muhammad Yar, Ahmad Danial Azzahari, Vidhya Selvanathan, Faridah Sonsudin and Cheyma Naceur Abouloula
Polymers 2017, 9(4), 137; https://doi.org/10.3390/polym9040137 - 12 Apr 2017
Cited by 559 | Viewed by 36480
Abstract
Improving the safety efficacy ratio of existing drugs is a current challenge to be addressed rather than the development of novel drugs which involve much expense and time. The efficacy of drugs is affected by a number of factors such as their low [...] Read more.
Improving the safety efficacy ratio of existing drugs is a current challenge to be addressed rather than the development of novel drugs which involve much expense and time. The efficacy of drugs is affected by a number of factors such as their low aqueous solubility, unequal absorption along the gastrointestinal (GI) tract, risk of degradation in the acidic milieu of the stomach, low permeation of the drugs in the upper GI tract, systematic side effects, etc. This review aims to enlighten readers on the role of pH sensitive hydrogels in drug delivery, their mechanism of action, swelling, and drug release as a function of pH change along the GI tract. The basis for the selection of materials, their structural features, physical and chemical properties, the presence of ionic pendant groups, and the influence of their pKa and pKb values on the ionization, consequent swelling, and targeted drug release are also highlighted. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Hydrogel matrix; (<b>b</b>) physically cross-linked hydrogel matrix; (<b>c</b>) chemically cross-linked hydrogel matrix.</p> Full article ">Figure 2
<p>Complete classification of hydrogels based on different factors.</p> Full article ">Figure 3
<p>(<b>a</b>) The four broad areas of smart hydrogels, (<b>b</b>) stimuli sensitive swelling of hydrogels along with their categories, (i) physical stimuli, (ii) chemical stimuli, and (iii) biological stimuli.</p> Full article ">Figure 4
<p>(<b>a</b>) pH dependent ionization of specific acidic or basic functional groups on hydrogel chains responsible for swelling, (<b>b</b>) pH dependent swelling and drug release mechanism.</p> Full article ">Figure 5
<p>Structure of (<b>a</b>) chitin, (<b>b</b>) chitosan, (<b>c</b>) glycosaminoglycan, (<b>d</b>) carboxymethyl chitosan, (<b>e</b>) <span class="html-italic">N</span>-succinyl chitosan and (<b>f</b>) guar gum.</p> Full article ">Figure 6
<p>Structure of guar gum succinate.</p> Full article ">Figure 7
<p>Structure of (<b>a</b>) Kappa-carrageenan, (<b>b</b>) Iota-Carrageenan, (<b>c</b>) Lambda-carrageenan, (<b>d</b>) dextran.</p> Full article ">Figure 8
<p>Chemical structure of Xanthan.</p> Full article ">Figure 9
<p>Structures of (<b>a</b>) cellulose (<b>b</b>) alpha-<span class="html-small-caps">l</span>-guluronic acid and beta-<span class="html-small-caps">d</span>-mannuronic acid (the epimers), (<b>c</b>) alginic acid (so called alginate), (<b>d</b>) arrangements of M and G residues as M and G blocks.</p> Full article ">Figure 10
<p>Structures of (<b>a</b>) poly(acrylic acid), (<b>b</b>) poly(acrylamide), (<b>c</b>) poly(vinyl alcohol), (<b>d</b>) poly(ethylene glycol), (<b>e</b>) poly(vinyl pyrrolidone), (<b>f</b>) poly(lactic acid).</p> Full article ">Figure 11
<p>Applications of hydrogels in different biomedical fields.</p> Full article ">Figure 12
<p>Drug delivery development from basic research to applications.</p> Full article ">
6357 KiB  
Article
Novel Magnet and Thermoresponsive Chemosensory Electrospinning Fluorescent Nanofibers and Their Sensing Capability for Metal Ions
by Fang-Cheng Liang, Yi-Ling Luo, Chi-Ching Kuo, Bo-Yu Chen, Chia-Jung Cho, Fan-Jie Lin, Yang-Yen Yu and Redouane Borsali
Polymers 2017, 9(4), 136; https://doi.org/10.3390/polym9040136 - 10 Apr 2017
Cited by 28 | Viewed by 6400
Abstract
Novel multifunctional switchable chemosensors based on fluorescent electrospun (ES) nanofibers with sensitivity toward magnetism, temperature, and mercury ions (Hg2+) were prepared using blends of poly(N-isopropylacrylamide)-co-(N-methylolacrylamide)-co-(Acrylic acid), the fluorescent probe 1-benzoyl-3-[2-(2-allyl-1,3-dioxo-2,3-dihydro-1Hbenzo[de]isoquinolin-6-ylamino)-ethyl]-thiourea (BNPTU), and magnetite nanoparticles (NPs), and a single-capillary spinneret. The moieties [...] Read more.
Novel multifunctional switchable chemosensors based on fluorescent electrospun (ES) nanofibers with sensitivity toward magnetism, temperature, and mercury ions (Hg2+) were prepared using blends of poly(N-isopropylacrylamide)-co-(N-methylolacrylamide)-co-(Acrylic acid), the fluorescent probe 1-benzoyl-3-[2-(2-allyl-1,3-dioxo-2,3-dihydro-1Hbenzo[de]isoquinolin-6-ylamino)-ethyl]-thiourea (BNPTU), and magnetite nanoparticles (NPs), and a single-capillary spinneret. The moieties of N-isopropylacrylamide, N-methylolacrylamide, acrylic acid, BNPTU, and Iron oxide (Fe3O4) NPs were designed to provide thermoresponsiveness, chemical cross-linking, Fe3O4 NPs dispersion, Hg2+ sensing, and magnetism, respectively. The prepared nanofibers exhibited ultrasensitivity to Hg2+ (as low as 10−3 M) because of an 80-nm blueshift of the emission maximum (from green to blue) and 1.6-fold enhancement of the emission intensity, as well as substantial volume (or hydrophilic to hydrophobic) changes between 30 and 60 °C, attributed to the low critical solution temperature of the thermoresponsive N-isopropylacrylamide moiety. Such temperature-dependent variations in the presence of Hg2+ engendered distinct on–off switching of photoluminescence. The magnetic ES nanofibers can be collected using a magnet rather than being extracted through alternative methods. The results indicate that the prepared multifunctional fluorescent ES nanofibrous membranes can be used as naked eye sensors and have the potential for application in multifunctional environmental sensing devices for detecting metal ions, temperature, and magnetism as well as for water purification sensing filters. Full article
(This article belongs to the Special Issue Polymers for Chemosensing)
►▼ Show Figures

Figure 1

Figure 1
<p>Synthesis of BNPTU fluorescent monomer.</p> Full article ">Figure 2
<p>Design of multifunctional sensory electro spun (ES) nanofibers synthesized from poly(NIPAAm-<span class="html-italic">co</span>-NMA-<span class="html-italic">co</span>-AA), BNPTU, and Fe<sub>3</sub>O<sub>4</sub> blends with magnetic fluorescence emission. (<b>a</b>) Polymerization and chemical structure of poly(NIPAAm-<span class="html-italic">co</span>-NMA-<span class="html-italic">co</span>-AA), BNPTU, and Fe<sub>3</sub>O<sub>4</sub> particles. (<b>b</b>) Fabrication of ES nanofibers from the blends. (<b>c</b>) Change in the chemical structure of BNPTU in solutions containing Hg<sup>2+</sup>. The fluorescence emission from the ES nanofibers exhibited color changes. A magnet can directly attract the ES nanofibers because of the magnetism of Fe<sub>3</sub>O<sub>4</sub> NPs.</p> Full article ">Figure 3
<p><sup>1</sup>H-NMR spectra recorded for (<b>a</b>) BN-Br in CDCl<sub>3</sub>, (<b>b</b>) BN-NH<sub>2</sub> in DMSO-<span class="html-italic">d</span><sub>6</sub>, and (<b>c</b>) BNPTU monomer in DMSO-<span class="html-italic">d</span><sub>6</sub>.</p> Full article ">Figure 3 Cont.
<p><sup>1</sup>H-NMR spectra recorded for (<b>a</b>) BN-Br in CDCl<sub>3</sub>, (<b>b</b>) BN-NH<sub>2</sub> in DMSO-<span class="html-italic">d</span><sub>6</sub>, and (<b>c</b>) BNPTU monomer in DMSO-<span class="html-italic">d</span><sub>6</sub>.</p> Full article ">Figure 4
<p><sup>1</sup>H-NMR spectrum of poly(NIPAAm-<span class="html-italic">co</span>-NMA-<span class="html-italic">co</span>-AA) in DMSO.</p> Full article ">Figure 5
<p>UV–Vis spectra of (<b>a</b>) BNPTU in CH<sub>3</sub>CN solution (10<sup>−5</sup> M) and (<b>b</b>) variation of UV–Vis spectra of BNPTU CH<sub>3</sub>CN solution (10<sup>−5</sup> M, pH 7) with different metal ions at 10<sup>−4</sup> M. The corresponding inset figures show the color changes under visible light and 254-nm UV light.</p> Full article ">Figure 6
<p>Field-emission scanning electron microscopy (FE-SEM) images of copolymers. (<b>a</b>) <b>P1</b> and (<b>b</b>) <b>P2</b> cross-linked nanofibers at 120 °C in a dry state and treated with water at 30 and 60 °C.</p> Full article ">Figure 7
<p>(<b>a</b>) FE-SEM and (<b>b</b>) Transmission electron microscopy (TEM) images of Fe<sub>3</sub>O<sub>4</sub> NPs synthesized through coprecipitation. (<b>c</b>) Magnetic Fe<sub>3</sub>O<sub>4</sub> NPs in the solution (left: Fe<sub>3</sub>O<sub>4</sub> precipitated out of the solution and dropped to the bottom; right: Fe<sub>3</sub>O<sub>4</sub> accumulated on the side of the bottle because of the magnet).</p> Full article ">Figure 8
<p>(<b>a</b>) SEM image of Fe<sub>3</sub>O<sub>4</sub> NPs blended with nanofibers at a 5% weight ratio. (<b>b</b>) FE-SEM image of <b>P2-5%</b> cross-linked nanofibers in the presence of Fe<sup>3+</sup>. (<b>c</b>,<b>d</b>) Energy dispersive X-ray spectroscopy EDS maps of C and Fe within the confined area in (b). (<b>e</b>) EDS spectrum recorded within the region defined in (b).</p> Full article ">Figure 9
<p>(<b>a</b>) Photoluminescence (PL) spectra of <b>P1</b> and <b>P2</b> nanofibers blended with 10 wt % BNPTU. (<b>b</b>) Comparison of <b>P2-5%</b> nanofibers with different Hg<sup>2+</sup> concentrations between 10<sup>−2</sup>, 10<sup>−3</sup> and 10<sup>−4</sup> M in aqueous solution. (<b>c</b>) Relative fluorescence intensity changes (<span class="html-italic">I</span><sub>450</sub>/<span class="html-italic">I</span><sub>530</sub>) of <b>P2-5%</b> ES nanofibers in aqueous solutions with various Hg<sup>2+</sup> concentrations. (<b>d</b>) PL spectra of <b>P2-5%</b> ES nanofibers in 10<sup>−2</sup> M Hg<sup>2+</sup> solution with a temperature increase from 30 to 60 °C.</p> Full article ">Figure 9 Cont.
<p>(<b>a</b>) Photoluminescence (PL) spectra of <b>P1</b> and <b>P2</b> nanofibers blended with 10 wt % BNPTU. (<b>b</b>) Comparison of <b>P2-5%</b> nanofibers with different Hg<sup>2+</sup> concentrations between 10<sup>−2</sup>, 10<sup>−3</sup> and 10<sup>−4</sup> M in aqueous solution. (<b>c</b>) Relative fluorescence intensity changes (<span class="html-italic">I</span><sub>450</sub>/<span class="html-italic">I</span><sub>530</sub>) of <b>P2-5%</b> ES nanofibers in aqueous solutions with various Hg<sup>2+</sup> concentrations. (<b>d</b>) PL spectra of <b>P2-5%</b> ES nanofibers in 10<sup>−2</sup> M Hg<sup>2+</sup> solution with a temperature increase from 30 to 60 °C.</p> Full article ">Figure 10
<p>(<b>a</b>) Variation in the normalized PL spectra of <b>P2-5%</b> ES nanofibers in aqueous solutions with various metal ions (10<sup>−2</sup> M) and no cation (blank). (<b>b</b>) Fluorometric responses (<span class="html-italic">I</span><sub>450</sub>/<span class="html-italic">I</span><sub>530</sub>) of <b>P2-5%</b> ES nanofibers to various cations at 10<sup>−2</sup> M aqueous solutions. From left to right: Hg<sup>2+</sup>, Pb<sup>2+</sup>, Co<sup>2+</sup>, Cd<sup>2+</sup>, Mg<sup>2+</sup>, Ni<sup>2+</sup>, Zn<sup>2+</sup>, Fe<sup>2+</sup>, and Cu<sup>2+</sup>. All the inset figures show corresponding photographs recorded under UV light. Inset of (<b>b</b>): fluorimetric response of the <b>P2-5%</b> ES nanofibers to solutions containing various metal ions at 10<sup>−2</sup> M (as in (<b>b</b>)) when Hg<sup>2+</sup> at 10<sup>−2</sup> M is present.</p> Full article ">Figure 11
<p>(<b>a</b>) CIE coordinates of <b>P2-5%</b> ES nanofibers in pH 7 aqueous solutions and after the detection of Hg<sup>2+</sup> at 10<sup>−2</sup> M aqueous solutions. (<b>b</b>) Confocal microscopy images of the ES nanofibers. All the inset figures show corresponding photographs recorded under UV light. (<b>c</b>) Schematic of a sensory filter microfluidics system for real-time metal ion sensing using an ES nanofiber membrane. (<b>d</b>) Relative conductivity versus time of the prepared Hg<sup>2+</sup> solution in the microfluidics system.</p> Full article ">Figure 11 Cont.
<p>(<b>a</b>) CIE coordinates of <b>P2-5%</b> ES nanofibers in pH 7 aqueous solutions and after the detection of Hg<sup>2+</sup> at 10<sup>−2</sup> M aqueous solutions. (<b>b</b>) Confocal microscopy images of the ES nanofibers. All the inset figures show corresponding photographs recorded under UV light. (<b>c</b>) Schematic of a sensory filter microfluidics system for real-time metal ion sensing using an ES nanofiber membrane. (<b>d</b>) Relative conductivity versus time of the prepared Hg<sup>2+</sup> solution in the microfluidics system.</p> Full article ">Figure 12
<p>(<b>a</b>) Hysteresis loops of <b>P2-5%</b> ES nanofibers (5 wt % Fe<sub>3</sub>O<sub>4</sub> NPs) measured at 25 °C. (<b>b</b>) Schematic of a filter sensory membrane prepared from <b>P2-5%</b> ES nanofibers composed of poly(NIPAAm-<span class="html-italic">co</span>-NMA-<span class="html-italic">co</span>-AA)), BNPTU, and Fe<sub>3</sub>O<sub>4</sub> NPs blends to simultaneously chelate and sense Hg<sup>2+</sup>. A magnet can directly attract the <b>P2-5%</b> ES nanofibers because of the magnetism of Fe<sub>3</sub>O<sub>4</sub> NPs.</p> Full article ">
6113 KiB  
Article
A Facile Approach for Fabrication of Core-Shell Magnetic Molecularly Imprinted Nanospheres towards Hypericin
by Wenxia Cheng, Fengfeng Fan, Ying Zhang, Zhichao Pei, Wenji Wang and Yuxin Pei
Polymers 2017, 9(4), 135; https://doi.org/10.3390/polym9040135 - 7 Apr 2017
Cited by 38 | Viewed by 8081
Abstract
By taking advantage of the self-polymerization of dopamine on the surface of magnetic nanospheres in weak alkaline Tris-HCl buffer solution, a facile approach was established to fabricate core-shell magnetic molecularly imprinted nanospheres towards hypericin (Fe3O4@PDA/Hyp NSs), via a surface [...] Read more.
By taking advantage of the self-polymerization of dopamine on the surface of magnetic nanospheres in weak alkaline Tris-HCl buffer solution, a facile approach was established to fabricate core-shell magnetic molecularly imprinted nanospheres towards hypericin (Fe3O4@PDA/Hyp NSs), via a surface molecular imprinting technique. The Fe3O4@PDA/Hyp NSs were characterized by FTIR, TEM, DLS, and BET methods, respectively. The reaction conditions for adsorption capacity and selectivity towards hypericin were optimized, and the Fe3O4@PDA/Hyp NSs synthesized under the optimized conditions showed a high adsorption capacity (Q = 18.28 mg/g) towards hypericin. The selectivity factors of Fe3O4@PDA/Hyp NSs were about 1.92 and 3.55 towards protohypericin and emodin, respectively. In addition, the approach established in this work showed good reproducibility for fabrication of Fe3O4@PDA/Hyp. Full article
(This article belongs to the Special Issue Polymers for Chemosensing)
►▼ Show Figures

Figure 1

Figure 1
<p>FTIR spectra of Fe<sub>3</sub>O<sub>4</sub>@PDA/Hyp, Fe<sub>3</sub>O<sub>4</sub>@PDA, MNSs, Hypericin and polydopamine (PDA).</p> Full article ">Figure 2
<p>TEM images of the nanospheres (NSs) prepared: (<b>a</b>) Fe<sub>3</sub>O<sub>4</sub>@PDA NSs; (<b>b</b>) Fe<sub>3</sub>O<sub>4</sub>@PDA/Hyp NSs; (<b>c</b>,<b>d</b>) are the enlarged images corresponding to (<b>a</b>,<b>b</b>), respectively. Scale bar: 200 nm.</p> Full article ">Figure 3
<p>Effect of concentration of dopamine on specific absorption capacity (<span class="html-italic">Q</span><sub>s</sub>).</p> Full article ">Figure 4
<p>Effect of amount of hypericin (% of dopamine in mole) on specific absorption capacity (<span class="html-italic">Q</span><sub>s</sub>).</p> Full article ">Figure 5
<p>Effect of the ratio of acetone to Tris-HCl buffer (<span class="html-italic">v</span>/<span class="html-italic">v</span>) on specific adsorption capacity (<span class="html-italic">Q</span><sub>s</sub>).</p> Full article ">Figure 6
<p>Dynamic adsorption of hypericin on Fe<sub>3</sub>O<sub>4</sub>@PDA/Hyp and Fe<sub>3</sub>O<sub>4</sub>@PDA NSs.</p> Full article ">Figure 7
<p>(<b>a</b>) The adsorption isotherm of Fe<sub>3</sub>O<sub>4</sub>@PDA/Hyp NSs towards hypericin; (<b>b</b>) The fitting plot of the adsorption isotherm of Fe<sub>3</sub>O<sub>4</sub>@PDA/Hyp NSs towards hypericin by Langmuir isotherm.</p> Full article ">Figure 8
<p>(<b>a</b>) The chemical structures of hypericin, protohypericin, and emodin; (<b>b</b>) Selective bindings of Fe<sub>3</sub>O<sub>4</sub>@PDA/Hyp (<b>black</b>) and Fe<sub>3</sub>O<sub>4</sub>@PDA (<b>red</b>) NSs toward to hypericin, protohypericin, and emodin, respectively.</p> Full article ">Figure 9
<p>Reproducibility study of the approach for fabrication of Fe<sub>3</sub>O<sub>4</sub>@PDA/Hyp NSs under the optimized conditions.</p> Full article ">Figure 10
<p>HPLC chromatograms. (<b>a</b>) the herb extract; (<b>b</b>) the mixture of the extract, hypericin and protohypericin before adsorption; (<b>c</b>) the supernatant after the adsorption of Fe<sub>3</sub>O<sub>4</sub>@PDA NSs; (<b>d</b>) the supernatant after the adsorption of Fe<sub>3</sub>O<sub>4</sub>@PDA/Hyp NSs.</p> Full article ">Scheme 1
<p>(<b>A</b>) Illustration of noncovalent bonding of template, hypericin with the functional monomer, dopamine: hydrogen bonding and π−π interaction; (<b>B</b>) Schematic illustration of fabricating Fe<sub>3</sub>O<sub>4</sub>@PDA/Hyp.</p> Full article ">
4931 KiB  
Article
Mechanical Performance of Graphene-Based Artificial Nacres under Impact Loads: A Coarse-Grained Molecular Dynamic Study
by Ning Liu, Ramana Pidaparti and Xianqiao Wang
Polymers 2017, 9(4), 134; https://doi.org/10.3390/polym9040134 - 7 Apr 2017
Cited by 17 | Viewed by 6124
Abstract
Inspired by the hierarchical structure and outstanding mechanical performance of biological nacre, we propose a similar multi-layered graphene–polyethylene nanocomposite as a possible lightweight material with energy-absorbing characteristics. Through coarse-grained molecular dynamics simulations, we study the mechanical performance of the nanocomposite under spall loading. [...] Read more.
Inspired by the hierarchical structure and outstanding mechanical performance of biological nacre, we propose a similar multi-layered graphene–polyethylene nanocomposite as a possible lightweight material with energy-absorbing characteristics. Through coarse-grained molecular dynamics simulations, we study the mechanical performance of the nanocomposite under spall loading. Results indicate that the polymer phase can serve as a cushion upon impact, which substantially decreases maximum contact forces and thus inhibits the breakage of covalent bonds in the graphene flakes. In addition, as the overlap distance in graphene layers increases, the energy absorption capacity of the model increases. Furthermore, the polymer phase can serve as a shield upon impact to protect the graphene phase from aggregation. The dependence of mechanical response on the size of impactors is also explored. Results indicate that the maximum contact force during the impact depends on the external surface area of impactors rather than the density of impactors and that the energy absorption for all model impactors is very similar. Overall, our findings can provide a systematic understanding of the mechanical responses on graphene–polyethylene nanocomposites under spall loads. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)
►▼ Show Figures

Figure 1

Figure 1
<p>Geometrical configurations of computational models. (<b>a</b>) Schematic view of the initial set-up of the simulation (red represents graphene fibers, blue represents polymer glues, and green represents impactors); (<b>b</b>) Impactors used in the simulations are named as Im<sub>1</sub>, Im<sub>2</sub>, and Im<sub>3</sub> (all with the same mass and the length of each impactor is 8.4 nm, the same size as the out-of-plane dimension of the sample); (<b>c</b>) The samples to be tested in the impact simulations are named as S<sub>1</sub>, S<sub>2</sub>, S<sub>3</sub>, S<sub>4</sub>, and S<sub>5</sub> (with polymer glues). The length of the sample is fixed at 48 nm while the overlap distance <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mrow> <mi>O</mi> <mi>L</mi> </mrow> </msub> </mrow> </semantics> </math> varies from 4 to 24 nm; (<b>d</b>) The samples to be tested in the impact simulations are named as S<sub>1</sub>’, S<sub>2</sub>’, S<sub>3</sub>’, S<sub>4</sub>’ and S<sub>5</sub>’ (without polymer glues).</p> Full article ">Figure 2
<p>Responses of the nanocomposites during impact simulations when the overlap distance <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mrow> <mi>O</mi> <mi>L</mi> </mrow> </msub> </mrow> </semantics> </math> is 24 nm (<b>a</b>) Reaction force; (<b>b</b>) Potential energy change.</p> Full article ">Figure 3
<p>Snapshots during impact simulations for samples (<b>a</b>) with polymers; (<b>b</b>) without polymers. The overlap distance <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mrow> <mi>O</mi> <mi>L</mi> </mrow> </msub> </mrow> </semantics> </math> is 24 nm. Spots where bond breaking happens are shadowed by orange circles).</p> Full article ">Figure 4
<p>(<b>a</b>) Maximum force on the nanocomposites caused by impactors; (<b>b</b>) Potential energy change during impact.</p> Full article ">Figure 5
<p>(<b>a</b>) Reaction force; (<b>b</b>) Zoomed-in view of <a href="#polymers-09-00134-f005" class="html-fig">Figure 5</a>a.</p> Full article ">Figure 6
<p>(<b>a</b>) Potential energy change; (<b>b</b>) Zoomed-in view of <a href="#polymers-09-00134-f006" class="html-fig">Figure 6</a>a.</p> Full article ">Figure 7
<p>Snapshots during the impact simulations for (<b>a</b>) Im<sub>1</sub> and S<sub>5</sub>; (<b>b</b>) Im<sub>2</sub> and S<sub>5</sub>; (<b>c</b>) Im<sub>3</sub> and S<sub>5</sub>; (<b>d</b>) Im<sub>1</sub> and S<sub>5</sub>’; (<b>e</b>) Im<sub>2</sub> and S<sub>5</sub>’; (<b>f</b>) Im<sub>3</sub> and S<sub>5</sub>’ when the overlap distance is 4 nm. The spots where bonds break are circled by dash lines.</p> Full article ">Figure 8
<p>The effect of overlap distance <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mrow> <mi>O</mi> <mi>L</mi> </mrow> </msub> </mrow> </semantics> </math> on (<b>a</b>) Maximum reaction force; (<b>b</b>) Potential energy change (Pe<sub>1</sub>); (<b>c</b>) Potential energy change (Pe<sub>2</sub>).</p> Full article ">
2421 KiB  
Article
Catalytic Activity of Oxidized Carbon Black and Graphene Oxide for the Crosslinking of Epoxy Resins
by Maria Rosaria Acocella, Carola Esposito Corcione, Antonella Giuri, Mario Maggio, Gaetano Guerra and Alfonso Maffezzoli
Polymers 2017, 9(4), 133; https://doi.org/10.3390/polym9040133 - 7 Apr 2017
Cited by 11 | Viewed by 6698
Abstract
This article compares the catalytic activities of oxidized carbon black (oCB) and graphene oxide (eGO) samples on the kinetics of a reaction of diglycidyl ether of bisphenol A (DGEBA) with a diamine, leading to crosslinked insoluble networks. The study is mainly conducted by [...] Read more.
This article compares the catalytic activities of oxidized carbon black (oCB) and graphene oxide (eGO) samples on the kinetics of a reaction of diglycidyl ether of bisphenol A (DGEBA) with a diamine, leading to crosslinked insoluble networks. The study is mainly conducted by rheometry and Differential Scanning Calorimetry (DSC). Following the same oxidation procedure, CB samples are more efficiently oxidized than graphite samples. For instance, CB and graphite samples with high specific surface areas (151 and 308 m2/g), as oxidized by the Hummers’ method, exhibit O/C wt/wt ratios of 0.91 and 0.62, respectively. Due to the higher oxidation levels, these oCB samples exhibit a higher catalytic activity toward the curing of epoxy resins than fully exfoliated graphene oxide. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2016)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>TGA scans at 10 °C/min after drying at 100 °C in the TGA apparatus, of starting Carbon black (CB) and all the considered carbon nanofillers: oCB-1; eGO; oCB-2; oCB-3. (<b>A</b>) TGA; (<b>B</b>) DTGA. Close to each curve, their O/C molar ratio is indicated.</p> Full article ">Figure 2
<p>FTIR spectra in the range 2000–400 cm<sup>−1</sup> of the considered carbon nanofillers: oCB-1; eGO; oCB-2; oCB-3. Close to each curve, their O/C molar ratio is indicated.</p> Full article ">Figure 3
<p>X-ray diffraction patterns (CuKα) of: graphene oxide (eGO, with O/C, wt/wt = 0.62); CB sample with the highest BET specific surface area; this CB after oxidation (oCB-3, O/C, wt/wt = 0.91). Patterns in the 2θ range 4–40° (<b>A</b>) and enlarged patterns in the 2θ range 40–85° (<b>B</b>).</p> Full article ">Figure 4
<p>Storage modulus (<b>G</b>′, empty symbols) and loss modulus (<b>G</b>″, full symbols) versus time for the DGEBA-IPDA epoxy resin, pure (<b>green</b>) or with 3 wt % of different carbon nanofillers: oCB-1 (O/C, wt/wt = 0.16) (<b>blue</b>); oCB-2 (O/C, wt/wt = 0.83 (<b>wine</b>); oCB-3 (O/C, wt/wt = 0.91) (<b>black</b>); eGO (O/C, wt/wt = 0.62) (<b>orange</b>).</p> Full article ">Figure 5
<p>DSC scans (heating rate = 10 °C/min) for the pure epoxy resin (<b>green</b>) and for composite resins with 3 wt % of: oCB-1 (<b>blue</b>); oCB-2 (<b>wine</b>); oCB-3 (<b>black</b>); eGO (<b>orange</b>).</p> Full article ">Figure 6
<p>Isothermal DSC scans at 50 °C of the DGEBA-IPDA epoxy resin. The lowest curve (<b>green</b>) corresponds to the neat epoxy resin. The other curves correspond to the epoxy resin filled by 3 wt % of different nanofillers: oCB-1 (O/C, wt/wt = 0.16) (<b>blue</b>); oCB-2 (O/C, wt/wt = 0.83) (<b>wine</b>) oCB-3 (O/C, wt/wt = 0.91) (<b>black</b>); eGO (O/C, wt/wt = 0.62) (<b>orange</b>).</p> Full article ">Figure 7
<p>Comparison between <span class="html-italic">d</span>α/<span class="html-italic">d</span>t experimental curves of each system: epoxy resin filled by 3 wt % of different nanofillers: oCB-1 (O/C, wt/wt = 0.16) (<b>blue</b>); oCB-2 (O/C, wt/wt = 0.83) (<b>wine</b>); oCB-3 (O/C, wt/wt = 0.91) (<b>black</b>); eGO (O/C, wt/wt = 0.62) (<b>orange</b>).</p> Full article ">Figure 8
<p>Comparison between Equation (6) model predictions and the experimental data of epoxy resins (<b>a</b>) filled by 3 wt % of different nanofillers; (<b>b</b>) oCB-1 (O/C, wt/wt = 0.16); (<b>c</b>) oCB-2 (O/C, wt/wt = 0.83); (<b>d</b>) oCB-3 (O/C, wt/wt = 0.91); (<b>e</b>) eGO (O/C, wt/wt = 0.62).</p> Full article ">Scheme 1
<p>Macromolecular structure of the reactants.</p> Full article ">
3096 KiB  
Article
Novel Polyvinyl Alcohol/Starch Electrospun Fibers as a Strategy to Disperse Cellulose Nanocrystals into Poly(lactic acid)
by Carol López de Dicastillo, Karina Roa, Luan Garrido, Alejandro Pereira and Maria Jose Galotto
Polymers 2017, 9(4), 117; https://doi.org/10.3390/polym9040117 - 7 Apr 2017
Cited by 21 | Viewed by 6477
Abstract
In this work, electrospun fibers of polyvinyl alcohol (PV) and starch (ST) were obtained to improve dispersion of cellulose nanocrystals (CNC) within a poly(lactic acid) (PLA) matrix with the aim of enhancing mechanical and barrier properties. The development and characterization of electrospun fibers [...] Read more.
In this work, electrospun fibers of polyvinyl alcohol (PV) and starch (ST) were obtained to improve dispersion of cellulose nanocrystals (CNC) within a poly(lactic acid) (PLA) matrix with the aim of enhancing mechanical and barrier properties. The development and characterization of electrospun fibers with and without CNC, followed by their incorporation in PLA at three concentrations (0.5%, 1% and 3% with respect to CNC) were investigated. Morphological, structural, thermal, mechanical and barrier properties of these nanocomposites were studied. The purpose of this study was not only to compare the properties of PLA nanocomposites with CNC embedded into electrospun fibers and nanocomposites with freeze-dried CNC, but also to study the effect of electrospinning process and the incorporation of CNC on the PV and starch properties. SEM micrographs confirmed the homogenous dispersion of fibers through PLA matrix. X-ray analysis revealed that the electrospinning process decreased the crystallinity of PV and starch. The presence of CNC enhanced the thermal stability of electrospun fibers. Electrospun fibers showed an interesting nucleating effect since crystallinity of PLA was strongly increased. Nanocomposites with electrospun fibers containing CNC presented slightly higher flexibility and ductility without decreasing barrier properties. Full article
(This article belongs to the Collection Polysaccharides)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>A</b>) macroscopic photograph of (PVST/CNC)<sub>f</sub> mat; (<b>B</b>) histogram of fiber diameter of (PVST)<sub>f</sub>; and (<b>C</b>) histogram of fiber diameter of (PVST/CNC)<sub>f</sub>.</p> Full article ">Figure 2
<p>Morphology of electrospun fibers: (<b>A</b>) (PVST/CNC)<sub>f</sub>, 10,000×; (<b>B</b>) (PVST/CNC)<sub>f</sub>, 40,000×; (<b>C</b>) (PVST)<sub>f</sub>, 10,000×; (<b>D</b>) (PVST)<sub>f</sub>, 40,000×.</p> Full article ">Figure 3
<p>SEM images of PLA composites: (<b>A</b>) PLA neat at: (<b>A1</b>) 2000×; (<b>A2</b>) 4000×; (<b>B</b>) 3PLA(PVST/CNC)<sub>f</sub> at: (<b>B1</b>) 4000×; (<b>B2</b>) 10,000×; (<b>C</b>) 3PLA(PVST)<sub>f</sub> at (<b>C1</b>) 2000×; (<b>C2</b>) 4000×; and (<b>D</b>) 3PLACNC at (<b>D1</b>) 2000×; (<b>D2</b>) 10,000×.</p> Full article ">Figure 4
<p>X-ray diffraction patterns of CNC (cellulose nanocrystals), electrospun fibers and PLA based composites.</p> Full article ">Figure 5
<p>(<b>A</b>) TGA (thermogravimetric analysis) curves of individual components. Insert: DTGA (derivative of the TGA curve) of curves; (<b>B</b>) DTGA of PLA based composites.</p> Full article ">Figure 6
<p>Images of developed PLA materials: (<b>A</b>) PLA; (<b>B</b>) 0.5PLA(PVST/CNC)<sub>f</sub>; (<b>C</b>) 1PLA(PVST/CNC)<sub>f</sub>; (<b>D</b>) 3PLA(PVST/CNC)<sub>f</sub>; (<b>E</b>) 0.5PLA(PVST)<sub>f</sub>; (<b>F</b>) 1PLA(PVST)<sub>f</sub>; (<b>G</b>) 3PLA(PVST)<sub>f</sub>; (<b>H</b>) 0.5PLACNC; (<b>I</b>) 1PLACNC; (<b>J</b>) 3PLACNC.</p> Full article ">
1617 KiB  
Article
Preparation, Characterization and Mechanical Properties of Bio-Based Polyurethane Adhesives from Isocyanate-Functionalized Cellulose Acetate and Castor Oil for Bonding Wood
by Adrián Tenorio-Alfonso, María Carmen Sánchez and José M. Franco
Polymers 2017, 9(4), 132; https://doi.org/10.3390/polym9040132 - 5 Apr 2017
Cited by 65 | Viewed by 11369
Abstract
Nowadays, different types of natural carbohydrates such as sugars, starch, cellulose and their derivatives are widely used as renewable raw materials. Vegetable oils are also considered as promising raw materials to be used in the synthesis of high quality products in different applications, [...] Read more.
Nowadays, different types of natural carbohydrates such as sugars, starch, cellulose and their derivatives are widely used as renewable raw materials. Vegetable oils are also considered as promising raw materials to be used in the synthesis of high quality products in different applications, including in the adhesive field. According to this, several bio-based formulations with adhesion properties were synthesized first by inducing the functionalization of cellulose acetate with 1,6-hexamethylene diisocyanate and then mixing the resulting biopolymer with a variable amount of castor oil, from 20% to 70% (wt). These bio-based adhesives were mechanically characterized by means of small-amplitude oscillatory torsion measurements, at different temperatures, and standardized tests to evaluate tension loading (ASTM-D906) and peel strength (ASTM-D903). In addition, thermal properties and stability of the synthesized bio-polyurethane formulations were also analyzed through differential scanning calorimetry and thermal gravimetric analysis. As a result, the performance of these bio-polyurethane products as wood adhesives were compared and analyzed. Bio-polyurethane formulations exhibited a simple thermo-rheological behavior below a critical temperature of around 80–100 °C depending on the castor oil/cellulose acetate weight ratio. Formulation with medium castor oil/biopolymer weight ratio (50:50 % wt) showed the most suitable mechanical properties and adhesion performance for bonding wood. Full article
(This article belongs to the Collection Polysaccharides)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Fourier transform infrared spectroscopic attenuated total reflectance (FTIR-ATR) spectra for: (<b>a</b>) 1,6-hexamethylene diisocyanate, cellulose acetate, castor oil and functionalized biopolymer; (<b>b</b>) formulation with 20% CO, 50% CO, 70% CO and 50% CO totally cured.</p> Full article ">Figure 2
<p>Thermogravimetric analysis (TGA) analysis for all bio-based adhesives.</p> Full article ">Figure 3
<p>(<b>a</b>) Loss weight and (<b>b</b>) derivative loss weight curves for cellulose acetate, 1,6-hexamethylene diisocyanate (HMDI) and CO raw materials.</p> Full article ">Figure 4
<p>Differential scanning calorimetry (DSC) thermograms for bio-based polyurethane samples studied.</p> Full article ">Figure 5
<p>Evolution of (<b>a</b>) elastic, <span class="html-italic">G</span>′, and (<b>b</b>) viscous moduli, <span class="html-italic">G</span>″, with frequency, within the linear viscoelastic range, for formulations containing 50% CO castor oil at different temperatures.</p> Full article ">Figure 6
<p><span class="html-italic">t</span>–<span class="html-italic">T</span> superposition for formulation with 50% CO from 25 up to 100 °C temperature.</p> Full article ">Figure 7
<p>(<b>a</b>) Shift factors (<span class="html-italic">a</span><sub>T</sub>) and (<b>b</b>) plateau moduli (<span class="html-italic">G</span><sub>N</sub><sup>0</sup>) for formulations with 50:50 and 70:30 castor oil/biopolymer weight ratios.</p> Full article ">Figure 8
<p>Temperature ramps for all ecofriendly bioadhesives at 2 °C/min of heating rate within the linear viscoelastic region: (<b>a</b>) elastic (<span class="html-italic">G</span>′) and viscous (<span class="html-italic">G</span>″) moduli; (<b>b</b>) loss tangent (tanδ).</p> Full article ">
663 KiB  
Article
Living Polymerization of Propylene with ansa-Dimethylsilylene(fluorenyl)(cumylamido) Titanium Complexes
by Huajin Wang, Xinwei Wang, Yanjie Sun, Hailong Cheng, Takeshi Shiono and Zhengguo Cai
Polymers 2017, 9(4), 131; https://doi.org/10.3390/polym9040131 - 5 Apr 2017
Cited by 4 | Viewed by 4849
Abstract
A series of ansa-silylene(fluorenyl)(amido) titanium complexes (1a–1c, 2a, and 2b) bearing various substituents on the amido and fluorenyl ligands are synthesized and characterized by elemental analysis, 1H NMR, and single crystal X-ray analysis. The coordination [...] Read more.
A series of ansa-silylene(fluorenyl)(amido) titanium complexes (1a–1c, 2a, and 2b) bearing various substituents on the amido and fluorenyl ligands are synthesized and characterized by elemental analysis, 1H NMR, and single crystal X-ray analysis. The coordination mode of the fluorenyl ligand to the titanium metal is η3 manner in each complex. The propylene polymerization is conducted with these complexes at 0 and 25 °C in a semi batch-type method, respectively. The catalytic activity of 1a–1c bearing cumyl-amido ligand is much higher than that of 2a and 2b bearing naphthyl group in amido ligand. High molecular weight polypropylenes are obtained with narrow molecular weight distribution, suggesting a living nature of these catalytic systems at 0 °C. The polymers produced are statistically atactic, regardless of the structure of the complex and the polymerization temperature. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Chemical diagrams of the <span class="html-italic">ansa</span>-(fluorenyl)(amido) titanium complexes studied.</p> Full article ">Figure 2
<p>Structure of fluorenylamidotitanium complexes <b>1a</b>, <b>1b</b>, <b>2a</b>, and <b>2b</b>. Hydrogen atoms are omitted for clarity. Atoms are drawn at the 40% probability level.</p> Full article ">
3031 KiB  
Article
Homoserine Lactone as a Structural Key Element for the Synthesis of Multifunctional Polymers
by Fabian Marquardt, Stefan Mommer, Justin Lange, Pascal M. Jeschenko, Helmut Keul and Martin Möller
Polymers 2017, 9(4), 130; https://doi.org/10.3390/polym9040130 - 5 Apr 2017
Cited by 7 | Viewed by 7504
Abstract
The use of bio-based building blocks for polymer synthesis represents a milestone on the way to “green” materials. In this work, two synthetic strategies for the preparation of multifunctional polymers are presented in which the key element is the functionality of homoserine lactone. [...] Read more.
The use of bio-based building blocks for polymer synthesis represents a milestone on the way to “green” materials. In this work, two synthetic strategies for the preparation of multifunctional polymers are presented in which the key element is the functionality of homoserine lactone. First, the synthesis of a bis cyclic coupler based on a thiolactone and homoserine lactone is displayed. This coupler was evaluated regarding its regioselectivity upon reaction with amines and used in the preparation of multifunctional polymeric building blocks by reaction with diamines. Furthermore, a linear polyglycidol was functionalized with homoserine lactone. The resulting polyethers with lactone groups in the side chain were converted to cationic polymers by reaction with 3-(dimethylamino)-1-propylamine followed by quaternization with methyl iodide. Full article
(This article belongs to the Special Issue Bio-inspired and Bio-based Polymers)
►▼ Show Figures

Figure 1

Figure 1
<p><sup>1</sup>H NMR spectrum of the thiolactone-lactone (<b>1</b>) measured in Deuterated dimethyl sulfoxide (DMSO-<span class="html-italic">d</span><sub>6</sub>).</p> Full article ">Figure 2
<p>DMF-SEC traces of the reaction of thiolactone-lactone coupler <b>1</b> with PEG-diamine and methyl acrylate at c = 0.5 M (<b>4a</b>, magenta), 1.0 M (<b>4b</b>, black), 1.5 M (<b>4c</b>, blue) and in bulk (<b>4d</b>, red).</p> Full article ">Figure 3
<p><sup>1</sup>H NMR spectrum of P(G<sup>HSL</sup>)<sub>26</sub> (<b>7</b>) measured in DMF-<span class="html-italic">d</span><sub>7</sub>.</p> Full article ">Scheme 1
<p>Strategies for the synthesis of glycerol carbonate and glycidol from glycerol [<a href="#B9-polymers-09-00130" class="html-bibr">9</a>].</p> Full article ">Scheme 2
<p>Overview of presented AB-monomers/couplers.</p> Full article ">Scheme 3
<p>Synthesis of the thiolactone-lactone coupler (<b>1</b>) from itaconic acid and thioacetic acid (<b>1.</b> THF, reflux, 4h; <b>2.</b> HCl, reflux, 6 h; <b>3.</b> TFA, reflux, 1 h; <b>4.</b> SOCl<sub>2</sub>, CHCl<sub>3</sub>, reflux, 6 h) (<b>a</b>), followed by reaction with DL-homoserine lactone hydrobromide and pyridine (rt, 16 h) (<b>b</b>).</p> Full article ">Scheme 4
<p>Model reactions to determine the regioselectivity of the amine addition with (<b>a</b>) 1 eq. hexylamine, deuterated dimethylformamide (DMF), rt and (<b>b</b>) 2 eq. hexylamine, DMF, 40 °C.</p> Full article ">Scheme 5
<p>Polyaddition reaction of PEG-Diamine to thiolactone-lactone coupler (<b>1</b>) in the presence of methyl acrylate. Products were synthesized in various concentrations of <b>1</b> in DMF (<b>4a</b>: 0.5 M; <b>4b</b>: 1.0 M; <b>4c</b>: 1.5 M) and in bulk (<b>4d</b>).</p> Full article ">Scheme 6
<p>Synthetic pathway to Poly(Glycidyl Homoserine Lactonylcarbamate)<sub>26</sub> (P(G<sup>HSL</sup>)<sub>26</sub>) (<b>7</b>). (<b>a</b>) Functionalization of PG<sub>26</sub> (<b>5</b>) with 4-nitrophenyl chloroformate, pyridine/DCM, rt, 20 h; (<b>b</b>) Reaction of P(G<sup>NPC</sup>)<sub>26</sub> (<b>6</b>) with DL-homoserine lactone hydrobromide, 4-DMAP, Et<sub>3</sub>N, DMF, rt, 20 h.</p> Full article ">Scheme 7
<p>Synthetic pathway to P(G<sup>HSL,o,q</sup>)<sub>26</sub> (<b>9</b>). (<b>a</b>) Addition of 3-(dimethylamino)-1-propylamine (DMAPA) to P(G<sup>HSL</sup>)<sub>26</sub> (<b>7</b>), DMF, rt, 20 h; (<b>b</b>) Quaternization of P(G<sup>HSL,o</sup>)<sub>26</sub> (<b>8</b>) with MeI, MeOH, reflux, 20 h.</p> Full article ">
2766 KiB  
Article
Preparation and Characterization of Water-Soluble Xylan Ethers
by Kay Hettrich, Ulrich Drechsler, Fritz Loth and Bert Volkert
Polymers 2017, 9(4), 129; https://doi.org/10.3390/polym9040129 - 31 Mar 2017
Cited by 18 | Viewed by 7993
Abstract
Xylan is a predominant hemicellulose component that is found in plants and in some algae. This polysaccharide is made from units of xylose (a pentose sugar). One promising source of xylan is oat spelt. This feedstock was used for the synthesis of two [...] Read more.
Xylan is a predominant hemicellulose component that is found in plants and in some algae. This polysaccharide is made from units of xylose (a pentose sugar). One promising source of xylan is oat spelt. This feedstock was used for the synthesis of two xylan ethers. To achieve water soluble products, we prepared dihydroxypropyl xylan as a non-ionic ether on the one hand, and carboxymethyl xylan as an ionic derivative on the other hand. Different preparation methods like heterogeneous, pseudo-homogeneous, and homogeneous syntheses were compared. In the case of dihydroxypropyl xylan, the synthesis method did not significantly affect the degree of substitution (DS). In contrast, in the case of carboxymethyl xylan, clear differences of the DS values were found in dependence on the synthesis method. Xylan ethers with DS values of >1 could be obtained, which mostly show good water solubility. The synthesized ionic, as well as non-ionic, xylan ethers were soluble in water, even though the aqueous solutions showed slight turbidity. Nevertheless, stable, transparent, and stainable films could be prepared from aqueous solutions from carboxymethyl xylans. Full article
(This article belongs to the Special Issue Polymers for Aqueous Media)
►▼ Show Figures

Figure 1

Figure 1
<p>Structure of a xylan from annual plant [<a href="#B9-polymers-09-00129" class="html-bibr">9</a>] in comparison to cellulose; in both polymers the monomer units are linked together by β-(1 → 4) glycosidic bonds; AGU = anhydroglucose unit.</p> Full article ">Figure 2
<p>Reaction scheme of the preparation of dihydroxypropyl xylan.</p> Full article ">Figure 3
<p>Effect of the reaction conditions on the degree of substitution (DS) values of xylan, achieved with 2,3-epoxy-1-propanol.</p> Full article ">Figure 4
<p>Reagent efficiency in dependence on the amount of epoxypropanol engaged for the various methods used.</p> Full article ">Figure 5
<p>Solid-state <sup>13</sup>C-NMR (CP/MAS) spectra of selected dihydroxypropyl xylans.</p> Full article ">Figure 6
<p>Reaction scheme of the preparation of carboxymethyl xylan.</p> Full article ">Figure 7
<p>Effect of the reaction conditions on the DS values of xylan, achieved with monochloro acetic acid (MCA).</p> Full article ">Figure 8
<p>Reagent efficiency in dependence on the amount of used monochloroacetic acid (MCA) engaged for the various methods used.</p> Full article ">Figure 9
<p>Cold water soluble films of dyed carboxymethylated xylan, cast from aqueous solutions.</p> Full article ">
2607 KiB  
Article
DNA Compaction and Charge Inversion Induced by Organic Monovalent Ions
by Wenyan Xia, Yanwei Wang, Anthony Yang and Guangcan Yang
Polymers 2017, 9(4), 128; https://doi.org/10.3390/polym9040128 - 30 Mar 2017
Cited by 12 | Viewed by 5372
Abstract
DNA condensation and charge inversion usually occur in solutions of multivalent counterions. In the present study, we show that the organic monovalent ions of tetraphenyl chloride arsenic (Ph4As+) can induce DNA compaction and even invert its electrophoretic mobility by [...] Read more.
DNA condensation and charge inversion usually occur in solutions of multivalent counterions. In the present study, we show that the organic monovalent ions of tetraphenyl chloride arsenic (Ph4As+) can induce DNA compaction and even invert its electrophoretic mobility by single molecular methods. The morphology of condensed DNA was directly observed by atomic force microscopy (AFM) in the presence of a low concentration of Ph4As+ in DNA solution. The magnetic tweezers (MT) measurements showed that DNA compaction happens at very low Ph4As+ concentration (≤1 μM), and the typical step-like structures could be found in the extension-time curves of tethering DNA. However, when the concentration of Ph4As+ increased to 1 mM, the steps disappeared in the pulling curves and globular structures could be found in the corresponding AFM images. Electrophoretic mobility measurement showed that charge inversion of DNA induced by the monovalent ions happened at 1.6 mM Ph4As+, which is consistent with the prediction based on the strong hydrophobicity of Ph4As+. We infer that the hydrophobic effect is the main driving force of DNA charge inversion and compaction by the organic monovalent ion. Full article
(This article belongs to the Special Issue Bio-inspired and Bio-based Polymers)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>A schematic diagram of magnetic tweezers.</p> Full article ">Figure 2
<p>AFM observation of DNA complexes. Panel (<b>A</b>) λ-DNA in 5 mM Mg<sup>2+</sup> solution; Panels (<b>B</b>–<b>F</b>) DNA conformations at different concentrations (0.01, 0.05, 0.1, 0.5 and 1 mM, respectively) of As<sup>+</sup> in 5 mM Mg<sup>2+</sup> buffer.</p> Full article ">Figure 3
<p>The structure of DNA in mixture solution of various concentrations ((<b>A</b>) 0.1 mM; (<b>B</b>) 0.5 mM; (<b>C</b>) 1 mM) of As<sup>+</sup> and 1 mM Mg<sup>2+</sup>.</p> Full article ">Figure 4
<p>DNA structures in solution of (<b>A</b>) 0.01 mM spermine and (<b>B</b>) 0.5 mM As<sup>+</sup>.</p> Full article ">Figure 5
<p>DNA extension–time curves under the influence of Ph<sub>4</sub>As<sup>+</sup>. (<b>A</b>) The shrinking of DNA at pulling force 0.5 pN; (<b>B</b>) unraveling of DNA condensed structures.</p> Full article ">Figure 6
<p>DNA extension–time curves when (<b>A</b>) contracting and (<b>B</b>) stretching at various Ph<sub>4</sub>As<sup>+</sup> concentrations.</p> Full article ">Figure 7
<p>DNA extension–time curves at high concentrations ((<b>A</b>) 0.1 mM; (<b>B</b>) 0.5 mM; (<b>C</b>) 1 mM) of Ph<sub>4</sub>As<sup>+</sup>.</p> Full article ">Figure 8
<p>The curve of condensing force at different concentrations of Ph<sub>4</sub>As<sup>+</sup>.</p> Full article ">Figure 9
<p>Electrophoretic mobility of DNA vs. the concentration of Ph<sub>4</sub>As<sup>+</sup>.</p> Full article ">
2862 KiB  
Communication
Label-Free Colorimetric Detection of Influenza Antigen Based on an Antibody-Polydiacetylene Conjugate and Its Coated Polyvinylidene Difluoride Membrane
by Jae-pil Jeong, Eunae Cho, Deokgyu Yun, Taejoon Kim, Im-Soon Lee and Seunho Jung
Polymers 2017, 9(4), 127; https://doi.org/10.3390/polym9040127 - 30 Mar 2017
Cited by 16 | Viewed by 7780
Abstract
This study presents an antibody-conjugated polydiacetylene (PDA) and its coated polyvinylidene difluoride (PVDF) membrane. The M149 antibody was hybridized to nano-vesicles consisting of pentacosa-10,12-diynoic acid (PCDA) and dimyristoylphosphatidylcholine (DMPC). After photo-polymerization at 254 nm, the effects on the PDA by antigenic injection were [...] Read more.
This study presents an antibody-conjugated polydiacetylene (PDA) and its coated polyvinylidene difluoride (PVDF) membrane. The M149 antibody was hybridized to nano-vesicles consisting of pentacosa-10,12-diynoic acid (PCDA) and dimyristoylphosphatidylcholine (DMPC). After photo-polymerization at 254 nm, the effects on the PDA by antigenic injection were investigated with UV-vis spectroscopy, fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. Because PDA, an alternating ene-yne molecule, induces a blue-to-red color transition and an interesting fluorescent response by the distortion of its backbone, the biomolecular recognition of an antibody–antigen can be converted into an optical and fluorescent signal. Thus, an influenza antigen was successfully detected with the proposed label-free method. Furthermore, the vesicular system was improved by coating it onto a membrane type sensing platform for its stability and portability. The proposed antibody-PDA composite PVDF membrane has potential for rapid, easy and selective visualization of the influenza virus. Full article
(This article belongs to the Special Issue Polymers for Chemosensing)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Colorimetric response (CR%) of the antibody-PDA conjugates and unfunctionalized PDA against antigen concentrations. Inset shows the noticeable color change of antibody-PDA conjugate after the addition of virus antigen (33 µg/mL); (<b>b</b>) Fluorescence intensity of the antibody-PDA conjugates in the absence and presence of virus antigen. (NHS-1 = 10% NHS-PCDA, NHS-2 = 20% NHS-PCDA and NHS-3 = 30% NHS-PCDA) The virus antigen was added to the PDA system and incubated at 37 °C for 10 min.</p> Full article ">Figure 2
<p>(<b>a</b>) Visible spectroscopy for different antigen concentrations (0 (<b>black</b>), 3.3 (<b>blue</b>), 6.6 (<b>pink</b>), 16.5 (<b>brown</b>), 33 µg/mL (<b>red</b>)); (<b>b</b>) Correlation curve between the CR% and log (concentration of the virus antigen). All experiments were performed in triplicate.</p> Full article ">Figure 3
<p>Dynamic light scattering (DLS) profile of the antibody-conjugated PDA nano-vesicles. (<b>a</b>) Without virus antigen; (<b>b</b>) With virus antigen.</p> Full article ">Figure 4
<p>TEM images of the antibody-conjugated PDA nano-vesicles. (<b>a</b>) Without virus antigen; (<b>b</b>) With virus antigen.</p> Full article ">Figure 5
<p>(<b>a</b>) Optical and (<b>b</b>) fluorescent microscopic images of the antibody-PDA functionalized polyvinylidene difluoride (PVDF) membranes.</p> Full article ">Figure 6
<p>SEM images of the (<b>a</b>) original PVDF; (<b>b</b>) buffer-treated antibody-PDA coated PVDF; (<b>c</b>) BSA-treated antibody-PDA coated PVDF; and (<b>d</b>) virus antigen-treated antibody-PDA coated PVDF.</p> Full article ">Scheme 1
<p>Schematic illustration of the fabrication steps of the M149 antibody-conjugated polydiacetylene (PDA) for influenza A and B virus detection.</p> Full article ">
143 KiB  
Editorial
Renewable Polymeric Adhesives
by Antonio Pizzi
Polymers 2017, 9(4), 126; https://doi.org/10.3390/polym9040126 - 28 Mar 2017
Cited by 15 | Viewed by 4603
Abstract
The field of renewable polymeric adhesives has become a very active field of research in the last few years [...] Full article
(This article belongs to the Special Issue Renewable Polymeric Adhesives)
2800 KiB  
Article
A Gelated Colloidal Crystal Attached Lens for Noninvasive Continuous Monitoring of Tear Glucose
by Jia-Li Ruan, Cheng Chen, Jian-Hua Shen, Xue-Ling Zhao, Shao-Hong Qian and Zhi-Gang Zhu
Polymers 2017, 9(4), 125; https://doi.org/10.3390/polym9040125 - 28 Mar 2017
Cited by 76 | Viewed by 12565
Abstract
Patients of diabetes mellitus urgently need noninvasive and continuous glucose monitoring in daily point-of-care. As the tear glucose concentration has a positive correlation with that in blood, the hydrogel colloidal crystal integrated into contact lens possesses promising potential for noninvasive monitoring of glucose [...] Read more.
Patients of diabetes mellitus urgently need noninvasive and continuous glucose monitoring in daily point-of-care. As the tear glucose concentration has a positive correlation with that in blood, the hydrogel colloidal crystal integrated into contact lens possesses promising potential for noninvasive monitoring of glucose in tears. This paper presents a new glucose-responsive sensor, which consists a crystalline colloidal array (CCA) embedded in hydrogel matrix, attached onto a rigid gas permeable (RGP) contact lens. This novel sensing lens is able to selectively diffract visible light, whose wavelength shifts between 567 and 468 nm according to the alternation of the glucose concentration between 0 and 50 mM and its visible color change between reddish yellow, green, and blue. The detection limit of responsive glucose concentration can be reduced to 0.05 mM. Its combination with a contact lens endows it with excellent biocompatibility and portability, which shows great possibility for it to push the development of glucose-detecting devices into new era. Full article
(This article belongs to the Special Issue Polymers for Chemosensing)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The preparation route of the 4-BBA-PVA GCCA-lens.</p> Full article ">Figure 2
<p>The cytotoxicity of extraction of GCCA-lens in HCECs: CCK-8 assay of the attachment and proliferation viability (<span class="html-italic">p</span> &gt; 0.05 vs. control, <span class="html-italic">n</span> = 5).</p> Full article ">Figure 3
<p>IFM micrographs of HCECs cultured with varied concentration of extraction of GCCA-lens. (<b>a</b>) Cells’ growth morphology and migration path in 0–24 h, and their condition in 48 h was shown below in: (<b>b</b>) Green (AM) and red (PI) fluorescence micrographs and cells’ visible morphology in 48 h; (<b>c</b>) living cell statistical analysis (<span class="html-italic">p</span> &gt; 0.05 vs. control, <span class="html-italic">n</span> = 3). Scale bars of 250 μm were added for easier reading.</p> Full article ">Figure 4
<p>Swelling curves of PVA hydrogel, 4-BBA-PVA and PBA-PAM. (<b>a</b>) In 20 mM glucose solution; (<b>b</b>) In buffered media.</p> Full article ">Figure 5
<p>(<b>a</b>) Schematic diagram of GCCA’s diffraction phenomenon from the (111) planes of the crystalline colloidal array (CCA) with a FCC arrangement that follows Bragg’s law; (<b>b</b>) The SEM photographs of the colloidal crystal assembled from PS nanoshperes; (<b>c</b>) 4-BBA-modified PVA hydrogel coated colloidal crystal, the periodic arrangement was successfully embedded in the hydrogel matrix.</p> Full article ">Figure 6
<p>Diffraction wavelength of GCCA-lens shifted responsive to glucose concentration changing. (<b>a</b>) Visible color shift of GCCA-lens according to glucose concentration change; (<b>b</b>) The diffraction response at low glucose concentration (insert is the photograph of the GCCA-lens sample).</p> Full article ">Figure 7
<p>Diffraction wavelength shift under physiological tear glucose concentration (0.1–0.6 mM). Insert is the correlation curve between glucose concentration and diffraction wavelength.</p> Full article ">
1752 KiB  
Article
A Polyvinylpyrrolidone-Based Supersaturable Self-Emulsifying Drug Delivery System for Enhanced Dissolution of Cyclosporine A
by Dae Ro Lee, Myoung Jin Ho, Young Wook Choi and Myung Joo Kang
Polymers 2017, 9(4), 124; https://doi.org/10.3390/polym9040124 - 27 Mar 2017
Cited by 25 | Viewed by 7030
Abstract
A novel supersaturable self-emulsifying drug delivery system (S-SEDDS) of cyclosporine A (CyA)—a poorly water-soluble immunosuppressant—was constructed in order to attain an apparent concentration–time profile comparable to that of conventional SEDDS with reduced use of oil, surfactant, and cosolvent. Several hydrophilic polymers, including polyvinylpyrrolidone [...] Read more.
A novel supersaturable self-emulsifying drug delivery system (S-SEDDS) of cyclosporine A (CyA)—a poorly water-soluble immunosuppressant—was constructed in order to attain an apparent concentration–time profile comparable to that of conventional SEDDS with reduced use of oil, surfactant, and cosolvent. Several hydrophilic polymers, including polyvinylpyrrolidone (PVP), were employed as precipitation inhibitors in the conventional SEDDS, which consists of corn oil-mono-di-triglycerides, polyoxyl 40 hydrogenated castor oil, ethanol, and propylene glycol. PVP-incorporated pre-concentrate (CyA:vehicle ingredients:PVP = 1:4.5:0.3 w/v/w) spontaneously formed spherical droplets less than 120 nm within 7 min of being diluted with water. In an in vitro dialysis test in a biorelevant medium such as simulated fed and/or fasted state intestinal and/or gastric fluids, PVP-based S-SEDDS exhibited a higher apparent drug concentration profile compared to cellulose derivative-incorporated S-SEDDS, even displaying an equivalent concentration profile with that of conventional SEDDS prepared with two times more vehicle (CyA:vehicle ingredients = 1:9 w/v). The supersaturable formulation was physicochemically stable under an accelerated condition (40 °C/75% RH) over 6 months. Therefore, the novel formulation is expected to be a substitute for conventional SEDDS, offering a supersaturated state of the poorly water-soluble calcinurin inhibitor with a reduced use of vehicle ingredients. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>TEM micrographs of (<b>a</b>) CyA-loaded conventional SEDDS (F1) and (<b>b</b>) PVP-incorporated supersaturable SEDDS (S-SEDDS, F9).</p> Full article ">Figure 2
<p>In vitro apparent concentration profiles of CyA from the conventional SEDDS formulations in (<b>a</b>) fasted state simulated gastric fluid (FaSSGF); (<b>b</b>) fed state simulated gastric fluid (FeSSGF); (<b>c</b>) fasted state simulated intestinal fluid (FaSSIF); and (<b>d</b>) fed state simulated intestinal fluid (FeSSIF) medium prepared with different amounts of vehicle components: 900 mg (F1, □), 675 mg (F2, <b>△</b>), and 450 mg (F3, ◊). The amount of drug in each formulation was equivalent to 100 mg, and the data are expressed as mean ± SD (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 3
<p>In vitro apparent concentration profiles of CyA in FeSSIF medium from the conventional SEDDS formulation (F3, ◊) and from S-SEDDS formulations containing different polymeric materials as precipitation inhibitors: HPC—(F4, <b>×</b>), Kollidon VA64—(F5, ●), and PVP-incorporated S-SEDDS (F6, ▲) formulas. The amount of polymeric materials in the S-SEDDS formulations was fixed at 15 mg, and the data are expressed as mean ± SD (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 4
<p>In vitro apparent concentration profiles of CyA in FeSSIF medium from the conventional SEDDS formulation (F1, □) and from PVP-based S-SEDDS formulations prepared with different amounts of hydrophilic polymer: 15 mg (F6, ▲), 20 mg (F7, <b>×</b>), 30 mg (F8, ●), and 40 mg (F9, ○). Data are expressed as mean ± SD (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 5
<p>In vitro apparent concentration profiles of CyA from the conventional SEDDS (F1, □) and from the optimized PVP-based S-SEDDS formulation (F8, ●) in different biorelevant media; (<b>a</b>) FaSSGF; (<b>b</b>) FeSSGF; and (<b>c</b>) FaSSIF. Data are expressed as mean ± SD (<span class="html-italic">n</span> = 3).</p> Full article ">
12378 KiB  
Article
Toxicity, Biocompatibility, pH-Responsiveness and Methotrexate Release from PVA/Hyaluronic Acid Cryogels for Psoriasis Therapy
by Cătălina Natalia Cheaburu Yilmaz, Daniela Pamfil, Cornelia Vasile, Nela Bibire, Raoul-Vasile Lupuşoru, Carmen-Lăcrămioara Zamfir and Cătălina Elena Lupușoru
Polymers 2017, 9(4), 123; https://doi.org/10.3390/polym9040123 - 27 Mar 2017
Cited by 34 | Viewed by 9163
Abstract
Poly(vinyl alcohol)/hyaluronic acid cryogels loaded with methotrexate were studied. The physical–chemical characterization of cryogels was performed by FT-IR spectroscopy, scanning electron microscopy, differential scanning calorimetry and dynamic mechanical thermal analysis. Acute toxicity and haematological parameters were determined by “in vivo” tests. The biocompatibility [...] Read more.
Poly(vinyl alcohol)/hyaluronic acid cryogels loaded with methotrexate were studied. The physical–chemical characterization of cryogels was performed by FT-IR spectroscopy, scanning electron microscopy, differential scanning calorimetry and dynamic mechanical thermal analysis. Acute toxicity and haematological parameters were determined by “in vivo” tests. The biocompatibility tests proved that the obtained cryogels showed significantly decreased toxicity and are biocompatible. The pH-responsiveness of the swelling behaviour and of the methotrexate release from the poly(vinyl alcohol)/hyaluronic acid (PVA/HA) cryogels were studied in a pH interval of 2–7.4. A significant change in properties was found at pH 5.5 specific for treatment of affected skin in psoriasis disease. Full article
(This article belongs to the Collection Polysaccharides)
►▼ Show Figures

Figure 1

Figure 1
<p>ATR-FT-IR spectra of HA/PVA unloaded and MTX-loaded cryogels (<b>a</b>) for the entire spectral range (<b>b</b>) for spectral range between 1800 and 500 cm<sup>−1</sup>.</p> Full article ">Figure 1 Cont.
<p>ATR-FT-IR spectra of HA/PVA unloaded and MTX-loaded cryogels (<b>a</b>) for the entire spectral range (<b>b</b>) for spectral range between 1800 and 500 cm<sup>−1</sup>.</p> Full article ">Figure 2
<p>SEM images of (<b>a</b>) HA/PVA 2c; (<b>b</b>) HA/PVA/MTX 2c; (<b>c</b>) HA/PVA 3c; (<b>d</b>) HAPVA/MTX 3c.</p> Full article ">Figure 3
<p>Differential scanning calorimetry (DSC) curves of the MTX and of unloaded and MTX-loaded PVA/HA cryogels.</p> Full article ">Figure 4
<p>Liver reactivity: in G1 (control), G2, G4 normal hepatic morphology was maintained; G3 revealed a dilated congestive central vein and inflammatory areas. The arrows in G3 indicate some alterations.</p> Full article ">Figure 5
<p>Kidney histopathologic exam revealed a normal renal structure for G1 (control), G2, G4, G3 revealed moderate grades of tubular epithelial degeneration. Hematoxylin–eosin (HE) stain, ob. ×20. The arrows in G3 indicate some alterations.</p> Full article ">Figure 6
<p>Cardiac histopathologic exam revealed a normal histologic aspect of the heart for G1 (control), G2, G3 and G4. HE stain, ob. ×20.</p> Full article ">Figure 7
<p>Pulmonary histopathologic exam revealed a normal configuration of the lungs for G1 (control), G2, G3 and G4. HE stain, ob. ×20.</p> Full article ">Figure 8
<p>Normal tissue morphology after topical administration of D2Y (G3T): (<b>a</b>) liver; (<b>b</b>) kidney; (<b>c</b>) heart; (<b>d</b>) lung. HE stain, ob. ×20.</p> Full article ">Figure 9
<p>Swelling profiles at different pHs values of the unloaded and MTX-loaded HA/PVA based matrices (<b>a</b>) and dependence of the <span class="html-italic">Q</span>e on pH (<b>b</b>).</p> Full article ">Figure 10
<p>Dependence of the <span class="html-italic">n</span><sub>sw</sub> (<b>a</b>) and <span class="html-italic">k</span><sub>sw</sub> (<b>b</b>) on pH.</p> Full article ">Figure 11
<p>Kinetic release profiles of MTX from HA/PVA-based cryogels (<b>a</b>) and variation of release amount at equilibrium (<span class="html-italic">Q</span><sub>er</sub>) with pH (<b>b</b>).</p> Full article ">Figure 12
<p>pH effect of on release parameters of MTX from PVA/HA matrices (<b>a</b>) diffusion exponent <span class="html-italic">n</span><sub>r</sub> and on the (<b>b</b>) kinetic constant <span class="html-italic">k</span><sub>r</sub>.</p> Full article ">
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-37
Previous Issue
Next Issue
Back to TopTop