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Polymers, Volume 12, Issue 1 (January 2020) – 250 articles

Cover Story (view full-size image): The isothermal nucleation, growth, and overall crystallization kinetics of biobased and biodegradable isodimorphic poly(butylene succinate)-ran-poly(ε-caprolactone) copolyesters (PBS-ran-PCL) were studied. Under isothermal conditions, only the PBS-rich phase or the PCL-rich phase crystallize, as long as the composition is away from the pseudo-eutectic point. The crystallization kinetics were a strong function of composition and supercooling. The only copolymer with a eutectic composition exhibited remarkable behavior. By tuning the crystallization temperature, this copolyester can form either one or two crystalline phases, each with remarkably different thermal properties. The properties of these versatile copolymers can be tailored by varying the composition and crystallization conditions. View this paper.
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18 pages, 8453 KiB  
Article
3D Printing On-Water Sports Boards with Bio-Inspired Core Designs
by Aref Soltani, Reza Noroozi, Mahdi Bodaghi, Ali Zolfagharian and Reza Hedayati
Polymers 2020, 12(1), 250; https://doi.org/10.3390/polym12010250 - 20 Jan 2020
Cited by 40 | Viewed by 9591
Abstract
Modeling and analyzing the sports equipment for injury prevention, reduction in cost, and performance enhancement have gained considerable attention in the sports engineering community. In this regard, the structure study of on-water sports board (surfboard, kiteboard, and skimboard) is vital due to its [...] Read more.
Modeling and analyzing the sports equipment for injury prevention, reduction in cost, and performance enhancement have gained considerable attention in the sports engineering community. In this regard, the structure study of on-water sports board (surfboard, kiteboard, and skimboard) is vital due to its close relation with environmental and human health as well as performance and safety of the board. The aim of this paper is to advance the on-water sports board through various bio-inspired core structure designs such as honeycomb, spiderweb, pinecone, and carbon atom configuration fabricated by three-dimensional (3D) printing technology. Fused deposition modeling was employed to fabricate complex structures from polylactic acid (PLA) materials. A 3D-printed sample board with a uniform honeycomb structure was designed, 3D printed, and tested under three-point bending conditions. A geometrically linear analytical method was developed for the honeycomb core structure using the energy method and considering the equivalent section for honeycombs. A geometrically non-linear finite element method based on the ABAQUS software was also employed to simulate the boards with various core designs. Experiments were conducted to verify the analytical and numerical results. After validation, various patterns were simulated, and it was found that bio-inspired functionally graded honeycomb structure had the best bending performance. Due to the absence of similar designs and results in the literature, this paper is expected to advance the state of the art of on-water sports boards and provide designers with structures that could enhance the performance of sports equipment. Full article
(This article belongs to the Special Issue The Next Generation of Smart Materials and 3D/4D Printing Technologies)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) A natural honeycomb structure; (<b>b</b>) the designed honeycomb core inspired by nature. (<b>c</b>) board components: the top shell, and the merged bottom shell and core.</p> Full article ">Figure 1 Cont.
<p>(<b>a</b>) A natural honeycomb structure; (<b>b</b>) the designed honeycomb core inspired by nature. (<b>c</b>) board components: the top shell, and the merged bottom shell and core.</p> Full article ">Figure 2
<p>Geometrical dimensions of the board with a honeycomb structure core (all the dimensions are in mm).</p> Full article ">Figure 3
<p>Sketch of TYPE 1 ASTM D638 specimen for the tensile test.</p> Full article ">Figure 4
<p>(<b>a</b>) Hounsfield-H25KS testing machine; (<b>b</b>) a dog-bone specimen under tensile test.</p> Full article ">Figure 5
<p>The stress–strain curve of the PLA tensile specimen.</p> Full article ">Figure 6
<p>(<b>a</b>) Two separate 3D-printed parts of the board; (<b>b</b>) two parts glued together with strong adhesive.</p> Full article ">Figure 7
<p>A schematic of the most common situations that boards break: (<b>a</b>) A standard boarding with a fine distance between the rider’s feet; (<b>b</b>) when the wave hits on the board while the rider falls in the water; (<b>c</b>) when the rider’s feet get so close together that the weight of their body is concentrated in the middle of the board.</p> Full article ">Figure 8
<p>The board with a uniform honeycomb structure core under three-point bending test.</p> Full article ">Figure 9
<p>I-shaped beam and the board with equivalent sections shown with orange lines.</p> Full article ">Figure 10
<p>Boundary conditions of the finite element method model.</p> Full article ">Figure 11
<p>FEM mesh convergence test of the board with a uniform honeycomb core structure.</p> Full article ">Figure 12
<p>Von Mises stress contour of the board with the uniform honeycomb core.</p> Full article ">Figure 13
<p>Comparison of the experimental, numerical, and analytical load–deflection curves for the three-point bending test of the honeycomb and fully-filled boards.</p> Full article ">Figure 14
<p>The value of the error function for the FEM and analytical results compared to the experimental results.</p> Full article ">Figure 15
<p>The bottom shell of the board with the hexagonal-rhombic structure.</p> Full article ">Figure 16
<p>Bottom shell with the triangular honeycomb core structure and detailed view of section. (<b>a</b>) Geometry and dimensions of a TH unit-cell (all dimensions are in mm).</p> Full article ">Figure 17
<p>(<b>a</b>) Carbon atoms placed in the six edges of a hexagon; (<b>b</b>) Bottom shell with the carbon atom configuration structure.</p> Full article ">Figure 18
<p>(<b>a</b>) A pinecone with two 8-number and 13-number opposite directional spirals; (<b>b</b>) Sunflower with Fibonacci spiral; (<b>c</b>) Pinecone-inspired structure designed using Fibonacci spirals.</p> Full article ">Figure 19
<p>(<b>a</b>) A schematic of a spiderweb; (<b>b</b>) The spiderweb-inspired pattern applied to the core of the board.</p> Full article ">Figure 20
<p>(<b>a</b>) A Bamboo stalk; (<b>b</b>) An optical image of the FG bamboo cross-section in which the dark areas are the fibers, while the light areas are the parenchyma matrices (adapted from [<a href="#B34-polymers-12-00250" class="html-bibr">34</a>]); (<b>c</b>) Graded honeycomb structure applied to the core of the board.</p> Full article ">Figure 21
<p>Reaction force–deflection curves for all of the tested structures.</p> Full article ">
35 pages, 14072 KiB  
Article
Thermodynamic and Transport Properties of Tetrabutylphosphonium Hydroxide and Tetrabutylphosphonium Chloride–Water Mixtures via Molecular Dynamics Simulation
by Brad Crawford and Ahmed E. Ismail
Polymers 2020, 12(1), 249; https://doi.org/10.3390/polym12010249 - 20 Jan 2020
Cited by 5 | Viewed by 5965
Abstract
Thermodynamic, structural, and transport properties of tetrabutylphosphonium hydroxide (TBPH) and tetrabutylphosphonium chloride (TBPCl)–water mixtures have been investigated using all-atom molecular dynamics simulations in response to recent experimental work showing the TBPH–water mixtures capability as a cellulose solvent. Multiple transitional states exist for the [...] Read more.
Thermodynamic, structural, and transport properties of tetrabutylphosphonium hydroxide (TBPH) and tetrabutylphosphonium chloride (TBPCl)–water mixtures have been investigated using all-atom molecular dynamics simulations in response to recent experimental work showing the TBPH–water mixtures capability as a cellulose solvent. Multiple transitional states exist for the water—ionic liquid (IL) mixture between 70 and 100 mol% water, which corresponds to a significant increase in water hydrogen bonds. The key transitional region, from 85 to 92.5 mol% water, which coincides with the mixture’s maximum cellulose solubility, reveals small and distinct water veins with cage structures formed by the TBP+ ions, while the hydroxide and chloride ions have moved away from the P atom of TBP+ and are strongly hydrogen bonded to the water. The maximum cellulose solubility of the TBPH–water solution at approximately 91.1 mol% water, appears correlated with the destruction of the TBP’s interlocking structure in the simulations, allowing the formation of water veins and channeling structures throughout the system, as well as changing from a subdiffusive to a near-normal diffusive regime, increasing the probability of the IL’s interaction with the cellulose polymer. A comparison is made between the solution properties of TBPH and TBPCl with those of alkylimidazolium-based ILs, for which water appears to act as anti-solvent rather than a co-solvent. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Cellulose solubility in tetrabutylphosphonium hydroxide (TBPH)-water solution as a function of water concentration for <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 298.15 K The experimental cellulose solubility ranges are shown throughout the paper, and were broken down into two different ranges. Light gray shading shows where cellulose is soluble, but not ideal (79.4 to 86.8 mol% water). Dark gray shading shows the maximum cellulose solubility range (86.8 to 93.9 mol% water). Data from Abe et al. [<a href="#B2-polymers-12-00249" class="html-bibr">2</a>].</p> Full article ">Figure 2
<p>Chemical structures of the molecules [<a href="#B34-polymers-12-00249" class="html-bibr">34</a>].</p> Full article ">Figure 3
<p>Simulated densities as a function of water concentration for <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K, are plotted against material safety data sheet (MSDS) values: (<b>a</b>) TBPH density compared to MSDS values for TBPH at 60 wt% water (95.8 mol% water) [<a href="#B37-polymers-12-00249" class="html-bibr">37</a>,<a href="#B38-polymers-12-00249" class="html-bibr">38</a>], TBAH at 45 wt% water (92.2 mol% water) [<a href="#B39-polymers-12-00249" class="html-bibr">39</a>], and 60 wt% water (95.6 mol% water) [<a href="#B40-polymers-12-00249" class="html-bibr">40</a>]; (<b>b</b>) TBPCl density compared to the MSDS value for tetrabutylammonium chloride (TBACl) at 50 wt% water (93.9 mol% water) [<a href="#B41-polymers-12-00249" class="html-bibr">41</a>].</p> Full article ">Figure 4
<p>Radial distribution functions of TBPH–water at 300 K for various indicated water concentrations. The radial distribution functions are between the following molecules: (<b>a</b>) OH<sup>−</sup>–OH<sup>−</sup>; (<b>b</b>) TBP<sup>+</sup>–TBP<sup>+</sup>; (<b>c</b>) TBP<sup>+</sup>–OH<sup>−</sup>; (<b>d</b>) TBP<sup>+</sup>–H<sub>2</sub>O; (<b>e</b>) H<sub>2</sub>O–H<sub>2</sub>O; (<b>f</b>) H<sub>2</sub>O–OH<sup>−</sup>.</p> Full article ">Figure 5
<p>(<b>a</b>) Radial distribution functions of the end carbons on the TBP’s butyl chains (C<sub>4</sub>-C<sub>4</sub>) for the TBPH–water solution at 300 K: Note that the 99.97 mol% water data is an order of magnitude higher than the other data since it was scaled down by 1/10 to fit on the same plot; (<b>b</b>) Radial distances of the end carbons on the TBP’s butyl chains (C<sub>4</sub>’s), within the same molecule [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>].</p> Full article ">Figure 6
<p>Average number of nearest molecularly identical neighbors in the largest cluster at 300 K: (<b>a</b>) the average number of waters that neighbor a water molecule; (<b>b</b>) the average number of TBPs that neighbor a TBP molecule.</p> Full article ">Figure 7
<p>Clustering data for water and TBP<sup>+</sup> ions at 300 K.</p> Full article ">Figure 8
<p>Representation of molecules in the TBPH–water solution. The blue-colored water is represented using an isosurface (called quicksurf in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]), which uses a volumetric Gaussian density map of the water to produce the observable surface. The TBP and OH molecules are represented using dynamic bonds in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]. TBP is colored tan, black and gray, for the phosphorus, carbon, and hydrogen atoms, respectively. The hydroxide is colored in red for both the oxygen and hydrogen atom.</p> Full article ">Figure 9
<p>Water veins and channeling in TBPH at 320K (Part 1 of 2) [<a href="#B27-polymers-12-00249" class="html-bibr">27</a>,<a href="#B28-polymers-12-00249" class="html-bibr">28</a>]. The Figures represent the changing water structure with increasing water concentration: (<b>a</b>) 63.1 mol% water; (<b>b</b>) 79.4 mol% water; (<b>c</b>) 86.8 mol% water; (<b>d</b>) 91.1 mol% water. The blue-colored water is represented using an isosurface drawing method (called quicksurf in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]), which uses a volumetric Gaussian density map of the water to produce the observable surface. The TBP and OH molecules are represented using the dynamic bonds drawing method in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]. TBP is colored tan, black and gray, for the phosphorus, carbon, and hydrogen atoms, respectively. The hydroxide is colored in red for both the oxygen and hydrogen atom.</p> Full article ">Figure 10
<p>Water veins and channeling in TBPH at 320K (Part 2 of 2) [<a href="#B27-polymers-12-00249" class="html-bibr">27</a>,<a href="#B28-polymers-12-00249" class="html-bibr">28</a>]. The Figures represent the changing water structure with increasing water concentration: (<b>a</b>) 93.9 mol% water; (<b>b</b>) 95.8 mol% water. The blue-colored water is represented using an isosurface drawing method (called quicksurf in visual molecular dynamics (VMD) [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]), which uses a volumetric Gaussian density map of the water to produce the observable surface. The tetrabutylphoshonium hydroxide (TBP) and OH molecules are represented using the dynamic bonds drawing method in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]. TBP is colored tan, black and gray, for the phosphorus, carbon, and hydrogen atoms, respectively. The hydroxide is colored in red for both the oxygen and hydrogen atom.</p> Full article ">Figure 11
<p>Geometric criteria for hydrogen bonds [<a href="#B50-polymers-12-00249" class="html-bibr">50</a>].</p> Full article ">Figure 12
<p>Average number of hydrogen bonds at 300 K: (<b>a</b>) cation–water pairs; (<b>b</b>) anion–water pairs; (<b>c</b>) water–water pairs; (<b>d</b>) cation–anion pairs. The first part of the labeling represents the per molecule basis (i.e., x-y represents the average number of hydrogen bonds between x and y per molecule of x).</p> Full article ">Figure 13
<p>(<b>a</b>) Excess molar volume and (<b>b</b>) excess molar enthalpy of mixing of TBPH and TBPCl as a function of water concentration at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K.</p> Full article ">Figure 14
<p>Heat capacity (<span class="html-italic">c<sub>p</sub></span>) of TBPH–water and TBPCl–water mixtures at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K on a (<b>a</b>) per gram basis and (<b>b</b>) per mole basis, in which the values are overlapping.</p> Full article ">Figure 15
<p>Thermal expansivity (<span class="html-italic">α<sub>p</sub></span>) constant for TBPH–water and TBPCl–water mixtures at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K as a function of water concentration.</p> Full article ">Figure 16
<p>Anomalous diffusion coefficients in TBPH–water at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K as a function of water concentration: (<b>a</b>) generalized diffusion coefficient, <span class="html-italic">K<sub>α</sub></span>; (<b>b</b>) anomalous diffusion exponent, <span class="html-italic">α</span>. The Grotthuss mechanism ReaxFF data was fitted to the anomalous diffusion equation with an assumed <span class="html-italic">α</span> value of 1 (original data from Zhang et al. [<a href="#B56-polymers-12-00249" class="html-bibr">56</a>]).</p> Full article ">Figure 17
<p>Particle-averaged time-averaged mean squared displacements (TAMSDs) of the TBPH–water solution at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K as a function of water concentration for: (<b>a</b>) <span class="html-italic">OH<sup>−</sup></span>; (<b>b</b>) water; (<b>c</b>) <span class="html-italic">TBP</span><sup>+</sup>.</p> Full article ">Figure 18
<p>Ergodicity breaking parameter (<span class="html-italic">χ</span>) in TBPH–water at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K as a function of water concentration and lag time for [<a href="#B34-polymers-12-00249" class="html-bibr">34</a>]: (<b>a</b>) <span class="html-italic">OH<sup>−</sup></span>; (<b>b</b>) water; (<b>a</b>) <span class="html-italic">TBP</span><sup>+</sup>.</p> Full article ">Figure 19
<p>Mean squared displacement (MSD) vs. particle-averaged TAMSD of the OH ion in TBPH–water at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K as a function of water concentration: (<b>a</b>) MSD and particle-averaged TAMSD of <span class="html-italic">OH<sup>−</sup></span> plotted on a log scale; (<b>b</b>) MSD and particle-averaged TAMSD of <span class="html-italic">OH<sup>−</sup></span> plotted on a linear scale. The colored lines are the MSDs, and the black lines are the particle-averaged TAMSDs.</p> Full article ">Figure A1
<p>Radial distribution functions of TBPCl–water at 300 K for various indicated water concentrations. The radial distribution functions are between the following molecules: (<b>a</b>) Cl<sup>−</sup>–Cl<sup>−</sup>; (<b>b</b>) TBP<sup>+</sup>–TBP<sup>+</sup>; (<b>c</b>) TBP<sup>+</sup>–Cl<sup>−</sup>; (<b>d</b>) TBP<sup>+</sup>–H<sub>2</sub>O; (<b>e</b>) H<sub>2</sub>O–H<sub>2</sub>O; (<b>f</b>) H<sub>2</sub>O–Cl<sup>−</sup>.</p> Full article ">Figure A2
<p>(<b>a</b>) Radial distribution functions of the end carbons on the TBP’s butyl chains (C<sub>4</sub>-C<sub>4</sub>) for the TBPCl–water solution at 300 K: Note that the 99.97 mol% water data is an order of magnitude higher than the other data since it was scaled down by 1/10 to fit on the same plot; (<b>b</b>) Radial distances of the end carbons on the TBP’s butyl chains (C4’s), within the same molecule [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>].</p> Full article ">Figure A3
<p>Water veins and channeling in TBPCl at 360 K (Part 1 of 2) [<a href="#B27-polymers-12-00249" class="html-bibr">27</a>,<a href="#B28-polymers-12-00249" class="html-bibr">28</a>]. The Figures represent the changing water structure with increasing water concentration: (<b>a</b>) 63.1 mol% water; (<b>b</b>) 79.4 mol% water; (<b>c</b>) 86.8 mol% water; (<b>d</b>) 91.1 mol% water. The blue-colored water is represented using an isosurface drawing method (called quicksurf in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]), which uses a volumetric Gaussian density map of the water to produce the observable surface. The TBP molecule is represented using dynamic bonds in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]. TBP is colored tan, black and gray, for the phosphorus, carbon, and hydrogen atoms, respectively. The green chloride is represented using the Van Der Walls (VDW) drawing method in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>].</p> Full article ">Figure A3 Cont.
<p>Water veins and channeling in TBPCl at 360 K (Part 1 of 2) [<a href="#B27-polymers-12-00249" class="html-bibr">27</a>,<a href="#B28-polymers-12-00249" class="html-bibr">28</a>]. The Figures represent the changing water structure with increasing water concentration: (<b>a</b>) 63.1 mol% water; (<b>b</b>) 79.4 mol% water; (<b>c</b>) 86.8 mol% water; (<b>d</b>) 91.1 mol% water. The blue-colored water is represented using an isosurface drawing method (called quicksurf in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]), which uses a volumetric Gaussian density map of the water to produce the observable surface. The TBP molecule is represented using dynamic bonds in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]. TBP is colored tan, black and gray, for the phosphorus, carbon, and hydrogen atoms, respectively. The green chloride is represented using the Van Der Walls (VDW) drawing method in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>].</p> Full article ">Figure A4
<p>Water veins and channeling in TBPCl at 360K (Part 2 of 2) [<a href="#B27-polymers-12-00249" class="html-bibr">27</a>,<a href="#B28-polymers-12-00249" class="html-bibr">28</a>]. The Figures represent the changing water structure with increasing water concentration: (<b>a</b>) 93.9 mol% water; (<b>b</b>) 95.8 mol% water. The blue-colored water is represented using an isosurface drawing method (called quicksurf in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]), which uses a volumetric Gaussian density map of the water to produce the observable surface. The TBP molecule is represented using dynamic bonds in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]. TBP is colored tan, black and gray, for the phosphorus, carbon, and hydrogen atoms, respectively. The green chloride is represented using the Van DerWalls (VDW) drawing method in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>].</p> Full article ">Figure A5
<p>Representation of molecules for the TBPCl–water solution. The blue-colored water is represented using an isosurface drawing method (called quicksurf in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]), which uses a volumetric Gaussian density map of the water to produce the observable surface. The TBP molecule is represented using dynamic bonds in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>]. TBP is colored tan, black and gray, for the phosphorus, carbon, and hydrogen atoms, respectively. The green chloride is represented using the Van Der Walls (VDW) drawing method in VMD [<a href="#B13-polymers-12-00249" class="html-bibr">13</a>].</p> Full article ">Figure A6
<p>Anomalous diffusion coefficients in TBPCl–water at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K as a function of water concentration: (<b>a</b>) generalized diffusion coefficient, <span class="html-italic">K<sub>a</sub></span>; (<b>b</b>) anomalous diffusion exponent, <span class="html-italic">α</span>.</p> Full article ">Figure A7
<p>Ergodicity breaking parameter (<span class="html-italic">χ</span>) in TBPCl–water at <span class="html-italic">p</span> = 1 atm and = 300 K as a function of water concentration and lag time for [<a href="#B34-polymers-12-00249" class="html-bibr">34</a>]: (<b>a</b>) <span class="html-italic">Cl</span><sup>−</sup>; (<b>b</b>) water; (<b>c</b>) <span class="html-italic">TBP</span><sup>+</sup>.</p> Full article ">Figure A8
<p>Particle-averaged TAMSDs of the TBPCl–water solution at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K as a function of water concentration for: (<b>a</b>) <span class="html-italic">Cl</span><sup>−</sup>; (<b>b</b>) water; (<b>c</b>) <span class="html-italic">TBP</span><sup>+</sup>.</p> Full article ">Figure A9
<p>MSD vs. particle-averaged TAMSD of the water, TBP and Cl in TBPCl–water at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K as a function of water concentration: (<b>a</b>) MSD and particle-averaged TAMSD of <span class="html-italic">Cl</span><sup>−</sup> plotted on a log scale; (<b>b</b>) MSD and particle-averaged TAMSD of <span class="html-italic">Cl</span><sup>−</sup> plotted on a linear scale; (<b>c</b>) MSD and particle-averaged TAMSD of water plotted on a log scale; (<b>d</b>) MSD and particle-averaged TAMSD of water plotted on a linear scale; (<b>e</b>) MSD and particle-averaged TAMSD of <span class="html-italic">TBP</span><sup>+</sup> plotted on a log scale; (<b>f</b>) MSD and particle-averaged TAMSD of <span class="html-italic">TBP</span><sup>+</sup> plotted on a linear scale. The colored lines are the MSDs, and the black lines are the particle-averaged TAMSDs.</p> Full article ">Figure A10
<p>MSD vs. particle-averaged TAMSD of the water, TBP and OH in TBPH–water at <span class="html-italic">p</span> = 1 atm and <span class="html-italic">T</span> = 300 K as a function of water concentration: (<b>a</b>) MSD and particle-averaged TAMSD of <span class="html-italic">OH</span><sup>−</sup> plotted on a log scale; (<b>b</b>) MSD and particle-averaged TAMSD of <span class="html-italic">OH</span><sup>−</sup> plotted on a linear scale; (<b>c</b>) MSD and particle-averaged TAMSD of water plotted on a log scale; (<b>d</b>) MSD and particle-averaged TAMSD of water plotted on a linear scale; (<b>e</b>) MSD and particle-averaged TAMSD of <span class="html-italic">TBP</span><sup>+</sup> plotted on a log scale; (<b>f</b>) MSD and particle-averaged TAMSD of <span class="html-italic">TBP</span><sup>+</sup> plotted on a linear scale.The colored lines are the MSDs, and the black lines are the particle-averaged TAMSDs.</p> Full article ">
19 pages, 4350 KiB  
Article
Geopolymer/CeO2 as Solid Electrolyte for IT-SOFC
by Jelena Gulicovski, Snežana Nenadović, Ljiljana Kljajević, Miljana Mirković, Marija Nišavić, Milan Kragović and Marija Stojmenović
Polymers 2020, 12(1), 248; https://doi.org/10.3390/polym12010248 - 20 Jan 2020
Cited by 19 | Viewed by 3752
Abstract
As a material for application in the life sciences, a new composite material, geopolymer/CeO2 (GP_CeO2), was synthesized as a potential low-cost solid electrolyte for application in solid oxide fuel cells operating in intermediate temperature (IT-SOFC). The new materials were obtained [...] Read more.
As a material for application in the life sciences, a new composite material, geopolymer/CeO2 (GP_CeO2), was synthesized as a potential low-cost solid electrolyte for application in solid oxide fuel cells operating in intermediate temperature (IT-SOFC). The new materials were obtained from alkali-activated metakaolin (calcined clay) in the presence of CeO2 powders (x = 10%). Besides the commercial CeO2 powder, as a source of ceria, two differently synthesized CeO2 powders also were used: CeO2 synthesized by modified glycine nitrate procedure (MGNP) and self-propagating reaction at room temperature (SPRT). The structural, morphological, and electrical properties of pure and GP_CeO2-type samples were investigated by X-ray powder diffraction (XRPD), Fourier transform infrared (FTIR), BET, differential thermal and thermogravimetric analysis (DTA/TGA), scanning electron microscopy (FE-SEM), energy dispersive spectrometer (EDS), and method complex impedance (EIS). XRPD and matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) analysis confirmed the formation of solid phase CeO2. The BET, DTA/TGA, FE-SEM, and EDS results indicated that particles of CeO2 were stabile interconnected and form a continuous conductive path, which was confirmed by the EIS method. The highest conductivity of 1.86 × 10−2 Ω−1 cm−1 was obtained for the sample GP_CeO2_MGNP at 700 °C. The corresponding value of activation energy for conductivity was 0.26 eV in the temperature range 500–700 °C. Full article
(This article belongs to the Section Polymer Applications)
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<p>X-ray diffraction pattern of pure geopolymer (GP) sample.</p> Full article ">Figure 2
<p>X-ray diffraction pattern of a GP_CeO<sub>2</sub>_com sample.</p> Full article ">Figure 3
<p>X-ray diffraction patterns of: (<b>a</b>) GP_CeO<sub>2</sub>_MGNP and (<b>b</b>) GP_CeO<sub>2</sub>_SPRT samples.</p> Full article ">Figure 4
<p>Fourier transform infrared (FTIR) spectrum of the metakaolin.</p> Full article ">Figure 5
<p>FTIR spectra of the CeO<sub>2</sub>_com, CeO<sub>2</sub>_MGNP, and CeO<sub>2</sub>_SPRT samples. MGNP: modified glycine nitrate procedure, SPRT: self-propagating reaction at room temperature.</p> Full article ">Figure 6
<p>FTIR spectra of the pure GP, GP_CeO2_com, GP_CeO2_MGNP, and GP_CeO2_SPRT samples.</p> Full article ">Figure 7
<p>Matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) analysis of (<b>a</b>) GP, (<b>b</b>) GP_CeO<sub>2</sub>_com, (<b>c</b>) GP_CeO<sub>2</sub>_SPRT and (<b>d</b>) GP_CeO<sub>2</sub>_MGNP.</p> Full article ">Figure 8
<p>(<b>a</b>) Nitrogen adsorption isotherm of pure GP, given as the amount of N<sub>2</sub> adsorbed as the function of a relative pressure, and (<b>b</b>) corresponding pore size distribution (PSD).</p> Full article ">Figure 9
<p>Results of the DTA/TGA analyses of: (<b>a</b>) GP, (<b>b</b>) GP_CeO<sub>2</sub>_com, (<b>c</b>) GP_CeO<sub>2</sub>_MGNP, and (<b>d</b>) GP_CeO<sub>2</sub>_SPRT.</p> Full article ">Figure 10
<p>SEM images of: (<b>a</b>) GP, (<b>b</b>) GP_CeO<sub>2</sub>_com, (<b>c</b>) GP_CeO<sub>2</sub>_ SPRT, (<b>d</b>) GP_CeO<sub>2</sub>_ MGNP, (<b>e</b>) and (<b>f</b>) corresponding energy dispersive spectrometer (EDS) spectra of grains and grain boundary GP_CeO<sub>2</sub>_MGNP.</p> Full article ">Figure 11
<p>Complex impedance plots of GP_CeO<sub>2</sub>_MGNP sample measured in different temperature ranges: (<b>a</b>) from 500 to 550 °C; (<b>b</b>) from 600 to 700 °C, in an air atmosphere. The arrows indicate the points on the real axis corresponding to the readings R<sub>b</sub> + R<sub>gb</sub>.</p> Full article ">Figure 12
<p>The dependence log κ = f(1/T) of the GP_CeO<sub>2</sub>_MGNP sample.</p> Full article ">
18 pages, 30468 KiB  
Article
Preparation, Characterization and Application of a Low Water-Sensitive Artemisia sphaerocephala Krasch. Gum Intelligent Film Incorporated with Anionic Cellulose Nanofiber as a Reinforcing Component
by Tieqiang Liang and Lijuan Wang
Polymers 2020, 12(1), 247; https://doi.org/10.3390/polym12010247 - 20 Jan 2020
Cited by 11 | Viewed by 3759
Abstract
A low-water-sensitive Artemisia sphaerocephala Krasch. gum (ASKG) based intelligent film was developed. Red cabbage extracts (RCE) was selected as a natural pH-sensitive indicator, and anionic cellulose nanofiber (ACNF) was added as a hydrophobic and locking host. The zeta potential, rheology, Fourier-transform infrared spectroscopy, [...] Read more.
A low-water-sensitive Artemisia sphaerocephala Krasch. gum (ASKG) based intelligent film was developed. Red cabbage extracts (RCE) was selected as a natural pH-sensitive indicator, and anionic cellulose nanofiber (ACNF) was added as a hydrophobic and locking host. The zeta potential, rheology, Fourier-transform infrared spectroscopy, X-ray diffractometry, and release results indicated that the RCE was locked by the ACNF via electrostatic interactions, moreover, broke the original complicated network and ordered arrangement of polymer molecules in the developed intelligent films. RCE addition decreased the tensile strength, oxygen, and water vapor barrier properties and light transmission of the developed intelligent films, while increasing the elongation at break. The films could respond to buffer solutions and NH3 through different color changes. The developed intelligent film was hydrophobic, which could precisely detect the freshwater shrimp freshness in real time via color changes, which indicated that the films have potential in intelligent packaging and gas-sensing label fields. Full article
(This article belongs to the Special Issue Advanced Biodegradable Polymers and Composites for Food Packaging)
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<p>Detecting experiment schematic.</p> Full article ">Figure 2
<p>Zeta potential of film-forming solution with different red cabbage extracts (RCE) amounts.</p> Full article ">Figure 3
<p>Effect of the RCE amount on steady rheological properties of film-forming solutions.</p> Full article ">Figure 4
<p>Effect of the RCE amount on dynamic rheological properties of film-forming solutions: AFR0 film-forming solution (<b>A</b>), AFR5 film-forming solution (<b>B</b>), AFR10 film-forming solution (<b>C</b>), and AFR15 film-forming solution (<b>D</b>).</p> Full article ">Figure 5
<p>Fourier-transform infrared (FT-IR) spectra of RCE and intelligent films: RCE (<b>a</b>), AFR0 (<b>b</b>), AFR5 (<b>c</b>), AFR10 (<b>d</b>), and AFR15 (<b>e</b>).</p> Full article ">Figure 6
<p>X-ray diffractometry (XRD) patterns of Artemisia sphaerocephala Krasch. gum (ASKG) (<b>a</b>), anionic cellulose nanofiber (ACNF) (<b>b</b>), AFR0 (<b>c</b>), AFR5 (<b>d</b>), AFR10 (<b>e</b>), and AFR15 (<b>f</b>) films.</p> Full article ">Figure 7
<p>Thermogravimetric (TG) and derivative thermogravimetric (DTG) curves of ASKG/ACNF/RCE intelligent films.</p> Full article ">Figure 8
<p>TEM picture (5000 magnification) of ACNF (<b>A</b>), SEM pictures (500 magnification) of the flat and cross-section surface morphology of intelligent films (<b>B</b>).</p> Full article ">Figure 9
<p>Effect of the RCE amount on mechanical properties of intelligent films.</p> Full article ">Figure 10
<p>Effect of the RCE amount on mechanical properties of intelligent films.</p> Full article ">Figure 11
<p>Effect of the RCE amount on oxygen barrier and water vapor barrier properties of intelligent films.</p> Full article ">Figure 12
<p>Effect of the RCE amount on light transparency properties of intelligent films.</p> Full article ">Figure 13
<p>Effect of the RCE amount on water contact angle of ASKG/ACNF/RCE intelligent films and ASKG/CMC·Na/RCE intelligent films.</p> Full article ">Figure 14
<p>Visible light absorption curves of RCE solution and filtrates.</p> Full article ">Figure 15
<p>The pH and total volatile basic nitrogen (TVB-N) values of freshness shrimp, colorimetric parameters (<b>A</b>) and photograph (<b>B</b>) of intelligent at different storage times.</p> Full article ">
24 pages, 12541 KiB  
Article
Mechanical Characterization of the Plastic Material GF-PA6 Manufactured Using FDM Technology for a Compression Uniaxial Stress Field via an Experimental and Numerical Analysis
by Jorge Manuel Mercado-Colmenero, Cristina Martin-Doñate, Vincenzo Moramarco, Michele Angelo Attolico, Gilda Renna, Moises Rodriguez-Santiago and Caterina Casavola
Polymers 2020, 12(1), 246; https://doi.org/10.3390/polym12010246 - 20 Jan 2020
Cited by 26 | Viewed by 6024
Abstract
This manuscript presents an experimental and numerical analysis of the mechanical structural behavior of Nylstrong GF-PA6, a plastic material manufactured using FDM (fused deposition modeling) technology for a compression uniaxial stress field. Firstly, an experimental test using several test specimens fabricated in the [...] Read more.
This manuscript presents an experimental and numerical analysis of the mechanical structural behavior of Nylstrong GF-PA6, a plastic material manufactured using FDM (fused deposition modeling) technology for a compression uniaxial stress field. Firstly, an experimental test using several test specimens fabricated in the Z and X-axis allows characterizing the elastic behavior of the reinforced GF-PA6 according to the ISO 604 standard for uniaxial compression stress environments in both Z and X manufacturing orientations. In a second stage, an experimental test analyzes the structural behavior of an industrial part manufactured under the same conditions as the test specimens. The experimental results for the test specimens manufactured in the Z and X-axis present differences in the stress-strain curve. Z-axis printed elements present a purely linear elastic behavior and lower structural integrity, while X-axis printed elements present a nonlinear elastic behavior typical of plastic and foam materials. In order to validate the experimental results, numerical analysis for an industrial part is carried out, defining the material GF-PA6 as elastic and isotropic with constant Young’s compression modulus according to ISO standard 604. Simulations and experimental tests show good accuracy, obtaining errors of 0.91% on the Z axis and 0.56% on the X-axis between virtual and physical models. Full article
(This article belongs to the Special Issue Functional Polymers in Additive Manufacturing)
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<p>Automotive assembly.</p> Full article ">Figure 2
<p>Topology of the studied end part.</p> Full article ">Figure 3
<p>FDM (fused deposition modeling) process configuration for the manufacture of the end part.</p> Full article ">Figure 4
<p>Requirements and load definition for the printed part.</p> Full article ">Figure 5
<p>3D printing process arrangement for X and Z axis printed specimens studied in the experimental test.</p> Full article ">Figure 6
<p>Test of uniaxial compression for specimens, testing machine Isntron 1342 and MTS634-31F-24 extensometer.</p> Full article ">Figure 7
<p>Curves for Z Axis manufactured specimens related to Uniaxial compression force versus nominal displacements.</p> Full article ">Figure 8
<p>Curves for X-Axis manufactured specimens related to Uniaxial compression force versus nominal displacements.</p> Full article ">Figure 9
<p>Curves for Z Axis manufactured specimens related to uniaxial compression stress versus nominal strains.</p> Full article ">Figure 10
<p>Curves for X-Axis manufactured specimens related to uniaxial compression stress versus nominal strains.</p> Full article ">Figure 11
<p>Uniaxial compression experimental test for the printed part under study.</p> Full article ">Figure 12
<p>Uniaxial compression load facing nominal displacements for the Z axis printed part tested.</p> Full article ">Figure 13
<p>Uniaxial compression load facing nominal displacements for the X-axis printed part tested.</p> Full article ">Figure 14
<p>Fracture of the printed part under study: (<b>A</b>) Z-Axis; (<b>B</b>) X-Axis, front view; (<b>C</b>) X-Axis, top view.</p> Full article ">Figure 15
<p>Set–up for the fracture surfaces analysis.</p> Full article ">Figure 16
<p>SEM images of Z-direction specimen—top view: (<b>A</b>) general view of the surface; (<b>B</b>) fracture surface of the contour line; (<b>C</b>) fiber rupture.</p> Full article ">Figure 17
<p>SEM images of the X-direction specimen—front view.</p> Full article ">Figure 18
<p>SEM images of X-direction specimen—lateral view.</p> Full article ">Figure 19
<p>Boundary requirements and loads used for the numerical simulations.</p> Full article ">Figure 20
<p>Mesh generated for the numerical simulation.</p> Full article ">Figure 21
<p>Field of displacements. (<b>A</b>) Z-axis printing direction; (<b>B</b>) X-axis printing direction.</p> Full article ">Figure 22
<p>Field of Von-Mises stress obtained in the mechanical simulations: (<b>A</b>) Z-axis printing direction; (<b>B</b>) X-axis printing direction.</p> Full article ">
15 pages, 3231 KiB  
Article
Chemical Characterization and Enzymatic Control of Stickies in Kraft Paper Production
by Lourdes Ballinas-Casarrubias, Guillermo González-Sánchez, Salvador Eguiarte-Franco, Tania Siqueiros-Cendón, Sergio Flores-Gallardo, Eduardo Duarte Villa, Miguel de Dios Hernandez, Beatriz Rocha-Gutiérrez and Quintín Rascón-Cruz
Polymers 2020, 12(1), 245; https://doi.org/10.3390/polym12010245 - 20 Jan 2020
Cited by 13 | Viewed by 4672
Abstract
Paper recycling has increased in recent years. A principal consequence of this process is the problem of addressing some polymeric components known as stickies. A deep characterization of stickies sampled over one year in a recycled paper industry in México was performed. Based [...] Read more.
Paper recycling has increased in recent years. A principal consequence of this process is the problem of addressing some polymeric components known as stickies. A deep characterization of stickies sampled over one year in a recycled paper industry in México was performed. Based on their chemical structure, an enzymatic assay was performed using lipases. Compounds found in stickies by Fourier-transform infrared spectrometry were poly (butyl-acrylate), dioctyl phthalate, poly (vinyl-acetate), and poly (vinyl-acrylate). Pulp with 4% (w/w) consistency and pH = 6.2 was sampled directly from the mill once macrostickies were removed. Stickies were quantified by counting the tacky macrostructures in the liquid fraction of the pulp using a Neubauer chamber before the paper was made, and they were analyzed with rhodamine dye and a UV lamp. Of the two commercial enzymes evaluated, the best treatment condition used Lipase 30 G (Specialty Enzymes & Biotechnologies Co®, Chino, CA, USA) at a concentration of 0.44 g/L, which decreased 35.59% of stickies. SebOil DG (Specialty Enzymes & Biotechnologies®) showed a stickies reduction of 21.5% when used at a concentration of 0.33 g/L. Stickies in kraft paper processes were actively controlled by the action of lipases, and future research should focus on how this enzyme recognizes its substrate and should apply synthetic biology to improve lipase specificity. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
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<p>TGA analysis curve for stickies 7B3CH.</p> Full article ">Figure 2
<p>Comparison of the FTIR spectra of the different fractions of 7B3, 7B4, and 7LS. (<b>a</b>) Ethanol extraction; (<b>b</b>) cyclohexane; (<b>c</b>) ethyl acetate; (<b>d</b>) dichloromethane.</p> Full article ">Figure 3
<p>Compounds found in stickies by FTIR. (<b>a</b>) PBA; (<b>b</b>) dioctyl phthalate; (<b>c</b>) poly (vinyl-acetate); (<b>d</b>) poly (styrene-acrylate).</p> Full article ">Figure 4
<p>Molecular characteristics of the commercial enzymes (Lipase 30 G and SebOil DG) were determined by the electrophoretic technique.</p> Full article ">Figure 5
<p>Effect of enzyme Lipase 30 G at different concentrations on the stickies. (<b>a</b>,<b>b</b>) control; (<b>c</b>) 0.11 g/L; (<b>d</b>) 0.22 g/L; (<b>e</b>) 0.33 g/L; and (<b>f</b>) 0.44 g/L. Large stikies are denoted by an arrow.</p> Full article ">Figure 6
<p>Stickies in paper using the rhodamine method. (<b>a</b>) No enzyme added; (<b>b</b>) treated with Lipase 30 G at 0.44 g/L. Large stikies are denoted by an arrow.</p> Full article ">
10 pages, 4205 KiB  
Article
Complementary Color Tuning by HCl via Phosphorescence-to-Fluorescence Conversion on Insulated Metallopolymer Film and Its Light-Induced Acceleration
by Shunichi Kaneko, Hiroshi Masai, Takuya Yokoyama, Maning Liu, Yasuhiro Tachibana, Tetsuaki Fujihara, Yasushi Tsuji and Jun Terao
Polymers 2020, 12(1), 244; https://doi.org/10.3390/polym12010244 - 20 Jan 2020
Cited by 9 | Viewed by 4068
Abstract
An insulated metallopolymer that undergoes phosphorescence-to-fluorescence conversion between complementary colors by an acid-stimulus is proposed as a color-tunable material. A Pt-based phosphorescent metallopolymer, where the conjugated polymeric backbone is insulated by a cyclodextrin, is depolymerized by HCl via acidic cleavage of Pt-acetylide bonds [...] Read more.
An insulated metallopolymer that undergoes phosphorescence-to-fluorescence conversion between complementary colors by an acid-stimulus is proposed as a color-tunable material. A Pt-based phosphorescent metallopolymer, where the conjugated polymeric backbone is insulated by a cyclodextrin, is depolymerized by HCl via acidic cleavage of Pt-acetylide bonds to form a fluorescent monomer. The insulation enables phosphorescence-to-fluorescence conversion to take place in the solid film. Rapid color change was achieved by accelerating the reaction between the metallopolymer and HCl by UV irradiation. These approaches are expected to provide new guidelines for the development of next-generation color-tunable materials and printable sensors based on precise molecular engineering. Full article
(This article belongs to the Special Issue Design and Synthesis of Conjugated Polymers for Electro-Optical Applications)
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<p>(<b>a</b>) Chromaticity diagram with arrows showing the yellow-to-green (A), red-to-yellow (B), and orange-to-white-to-blue (C) shifts. (<b>b</b>) Chemical structures and the photographic images (excitation at 365 nm) of emission under deoxygenated conditions for polymer <b>1</b> and polymer <b>2</b> films on SiO<sub>2</sub> substrates. (<b>c</b>) Conceptual illustrations of phosphorescence-to-fluorescence conversion between complementary colors, triggered by metallopolymer to monomer conversion (This study).</p> Full article ">Figure 2
<p>Depolymerizing experiments in the solution state: (<b>a</b>) Reaction of polymer <b>1</b> with HCl. (<b>b</b>) SEC analyses (detected at UV 380 nm) of the reaction products of polymer <b>1</b> before reaction (orange) and after reaction with 1 M HCl (gray) and 4 M HCl (blue) for 18 h. (<b>c</b>) Photographic images and (<b>d</b>) emission spectra of the reaction mixture of <b>1</b> by varying the concentration of HCl in (<b>c</b>), under deoxygenated conditions (excitation at 365 nm).</p> Full article ">Figure 3
<p>Depolymerizing experiments in the solid state: Emission photographs under deoxygenated conditions (excitation at 365 nm) of polymer <b>1</b> films on SiO<sub>2</sub> substrates (<b>a</b>) before reaction, and after reaction with HCl gas for (<b>b</b>) 1.5 h, and (<b>c</b>) 4 h. (<b>d</b>) Emission spectra of polymer <b>1</b> film in (<b>a</b>–<b>c</b>). Emission photographs of polymer <b>2</b> films (<b>e</b>) before reaction, and after reaction with HCl gas for (<b>f</b>) 10 min, and (<b>g</b>) 30 min, under the same conditions as (<b>a</b>–<b>c</b>). (<b>h</b>) Emission intensity ratio between 460 nm and 583 nm (excitation at 365 nm) of polymer <b>1</b> films on SiO<sub>2</sub> substrates in the presence of various gases after 3 h under deoxygenated conditions.</p> Full article ">Figure 4
<p>Experimental results of light-induced acceleration of polymer <b>1</b> film on SiO<sub>2</sub> substrate: (<b>a</b>) Photographic images (upon 365-nm excitation under deoxygenated conditions): Resultant substrate after 5% <span class="html-italic">v</span>/<span class="html-italic">v</span> HCl exposure for 5 min with UV irradiation of each wavelength range and an absorption spectrum of <b>1</b> in dilute CHCl<sub>3</sub>. (<b>b</b>) Photographic images (upon 365-nm excitation under deoxygenated conditions) of the resultant film with spot irradiations (350–400 nm) and 10% <span class="html-italic">v</span>/<span class="html-italic">v</span> HCl gas. (<b>c</b>) Photographic image of irradiation pattern in (<b>b</b>) with white light on black paper. (<b>d</b>) Photographic images (upon 365-nm excitation under deoxygenated conditions) before and after reaction with 500-ppm HCl gas for 2 min using light-induced acceleration.</p> Full article ">Figure 5
<p>Light-induced acceleration of Pt-acetylide complex <b>4</b>: (<b>a</b>) Chemical structure of <b>4</b> and monochlorinated Pt complex <b>5</b>. (<b>b</b>) <sup>31</sup>P NMR (202 MHz, CDCl<sub>3</sub>) analyses of <b>4</b> after reaction for 10 min under UV, HCl, and UV + HCl. Coupling peaks with platinum atom are in parentheses.</p> Full article ">
18 pages, 5999 KiB  
Article
Core/Sheath-Structured Composite Nanofibers Containing Cinnamon Oil: Their Antibacterial and Antifungal Properties and Acaricidal Effect against House Dust Mites
by Yoonwon Jung, Hyukjoo Yang, In-Yong Lee, Tai-Soon Yong and Seungsin Lee
Polymers 2020, 12(1), 243; https://doi.org/10.3390/polym12010243 - 20 Jan 2020
Cited by 18 | Viewed by 4013
Abstract
This study aimed to fabricate core/sheath-structured composite nanofibers containing cinnamon oil by emulsion electrospinning and to investigate their acaricidal effect on house dust mites as well as their antibacterial and antifungal properties in relation to cinnamon oil concentration in the nanofibers. An oil-in-water [...] Read more.
This study aimed to fabricate core/sheath-structured composite nanofibers containing cinnamon oil by emulsion electrospinning and to investigate their acaricidal effect on house dust mites as well as their antibacterial and antifungal properties in relation to cinnamon oil concentration in the nanofibers. An oil-in-water emulsion, which comprised cinnamon oil and poly(vinyl alcohol) solution as oil and water phases, respectively, was used to prepare core/sheath-structured nanofibers. The morphology and the inner structure of the electrospun nanofibers were observed by scanning electron microscopy and confocal laser scanning microscopy. Core/sheath-structured nanofibers containing cinnamon oil were successfully prepared by emulsion electrospinning. The composite nanofibers prepared from an emulsion containing 20 wt% of cinnamon oil exhibited a strong acaricidal effect against house dust mites (Dermatophagoides farinae). The composite nanofibers fabricated from an emulsion containing 4.29 wt% of cinnamon oil showed excellent antimicrobial effects against Staphylococcus aureus and a series of fungi that can trigger respiratory- and skin-related diseases. The release profile of cinnamon oil from the core/sheath-structured nanofibers showed a continuous release of functional ingredients over 28 days. Our findings demonstrate that the use of such fibrous structures could be a promising approach for delivering naturally derived bioactive agents in a controlled way. Full article
(This article belongs to the Special Issue Innovative Functional Textiles)
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<p>Experimental setup for assessing the acaricidal effects of nanofibrous membranes containing cinnamon oil on house dust mites.</p> Full article ">Figure 2
<p>SEM images of cinnamon oil-containing poly(vinyl alcohol) (PVA) nanofibers produced from different emulsion formulations: (<b>a</b>) emulsion A (10 wt% of PVA, 3.57 wt% of oil, and 0.71 wt% of surfactant), (<b>b</b>) emulsion B (11 wt% of PVA, 3.93 wt% of oil, and 0.79 wt% of surfactant), (<b>c</b>) emulsion C (12 wt% of PVA, 4.29 wt% of oil, and 0.86 wt% of surfactant), and (<b>d</b>) emulsion D (13 wt% of PVA, 4.64 wt% of oil, and 0.93 wt% of surfactant).</p> Full article ">Figure 3
<p>SEM images of cinnamon oil-containing PVA nanofibers produced under different processing conditions: (<b>a</b>) 0.2 mL/h, 23 G, (<b>b</b>) 0.2 mL/h, 25 G, (<b>c</b>) 0.5 mL/h, 23 G, (<b>d</b>) 0.5 mL/h, 25 G, (<b>e</b>) 0.8 mL/h, 23 G, (<b>f</b>) 0.8 mL/h, 25 G, (<b>g</b>) 1.2 mL/h, 23 G, and (<b>h</b>) 1.2 mL/h, 25 G. Applied voltage and tip-to-collector distance were maintained constant at 25 kV and 20 cm, respectively.</p> Full article ">Figure 4
<p>SEM image of cinnamon oil/PVA nanofiber webs from emulsion C (12 wt% of PVA, 4.29 wt% of cinnamon oil, and 0.86 wt% of surfactant) produced with a solution feed rate of 0.2 mL/h, a voltage of 25 kV, and a tip-to-collector distance of 20 cm through a 23-gauge needle.</p> Full article ">Figure 5
<p>CLSM images of cinnamon oil/PVA nanofibers from emulsion C: (<b>a</b>) Cinnamon oil was stained by Nile red and viewed with excitation at 515 nm. (<b>b</b>) PVA was stained by FITC and viewed with excitation at 492 nm.</p> Full article ">Figure 6
<p>SEM images of cinnamon oil-containing PVA nanofibers produced from emulsion formulations containing high concentrations of cinnamon oil: (<b>a</b>) emulsion F (8 wt% of oil, 12 wt% of PVA, and 1.6 wt% of surfactant), (<b>b</b>) emulsion G (15 wt% of cinnamon oil, 12 wt% of PVA, and 3 wt% of surfactant), (<b>c</b>) emulsion H (20 wt% of cinnamon oil, 12 wt% of PVA, and 4 wt% of surfactant), and (<b>d</b>) emulsion I (30 wt% of cinnamon oil, 12 wt% of PVA, and 6 wt% of surfactant). Solution feed rate, applied voltage, needle gauge, and tip-to-collector distance were maintained constant at 0.2 mL/h, 25 kV, 23-gauge, and 20 cm, respectively.</p> Full article ">Figure 7
<p>CLSM images of cinnamon oil/PVA nanofibers from emulsion H: (<b>a</b>–<b>c</b>) core/sheath structures of cinnamon oil/PVA nanofibers.</p> Full article ">Figure 8
<p>Antifungal activity of nanofibrous membranes containing cinnamon oil: (<b>a</b>) control specimen; and (<b>b</b>) nanofibers containing cinnamon oil.</p> Full article ">Figure 9
<p>Cumulative release of the major chemical components of cinnamon oil (cinnamaldehyde, eugenol, and caryophyllene) from nanofibrous membranes containing cinnamon oil.</p> Full article ">
9 pages, 2872 KiB  
Article
High-Repetition-Rate Femtosecond Laser Processing of Acrylic Intra-Ocular Lenses
by Daniel Sola and Rafael Cases
Polymers 2020, 12(1), 242; https://doi.org/10.3390/polym12010242 - 20 Jan 2020
Cited by 11 | Viewed by 3593
Abstract
The study of laser processing of acrylic intra-ocular lenses (IOL) by using femtosecond laser pulses delivered at high-repetition rate is presented in this work. An ultra-compact air-cooled femtosecond diode laser (HighQ2-SHG, Spectra-Physics) delivering 250 fs laser pulses at the fixed wavelength of 520 [...] Read more.
The study of laser processing of acrylic intra-ocular lenses (IOL) by using femtosecond laser pulses delivered at high-repetition rate is presented in this work. An ultra-compact air-cooled femtosecond diode laser (HighQ2-SHG, Spectra-Physics) delivering 250 fs laser pulses at the fixed wavelength of 520 nm with a repetition rate of 63 MHz was used to process the samples. Laser inscription of linear periodic patterns on the surface and inside the acrylic substrates was studied as a function of the processing parameters as well as the optical absorption characteristics of the sample. Scanning Electron Microscopy (SEM) Energy Dispersive X-ray Spectroscopy (EDX), and micro-Raman Spectroscopy were used to evaluate the compositional and microstructural changes induced by the laser radiation in the processed areas. Diffractive characterization was used to assess 1st-order efficiency and the refractive index change. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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<p>Optical transmission spectrum of acrylic intra-ocular lens. The arrow points out the laser wavelength used to process the sample, 520 nm, for which optical transmittance is 84.3%. Crystalline lens optical transmission spectrum is also included for comparison purposes.</p> Full article ">Figure 2
<p>Image of periodic patterns inscribed on the surface (<b>a</b>) and 150 µm underneath the sample surface (<b>b</b>) at 1 mm/s, 10 µm inter-line spacing and 2 nJ pulse energy.</p> Full article ">Figure 3
<p>Top-view SEM micrograph of a periodic pattern inscribed on the surface of the acrylic IOL with 1 nJ pulse energy at 0.25 mm/s (<b>a</b>), and profile of semi-quantitative composition of carbon and oxygen content along the pattern measured by EDX analysis (<b>b</b>). Oxygen content has been doubled for clarification purposes.</p> Full article ">Figure 4
<p>Micro-Raman spectra of non-processed acrylic IOL and processed areas on the surface and 150 µm underneath the surface.</p> Full article ">Figure 5
<p>Far-field diffraction image of the output beam transmitted through the periodic structure processed 150 µm underneath the surface, with 20 µm inter-line spacing and 1 nJ pulse energy at 0.50 mm/s.</p> Full article ">Figure 6
<p>1st-order efficiency (<b>a</b>) and refractive index change (<b>b</b>) of diffraction gratings inscribed 150 µm underneath the surface of the acrylic IOL.</p> Full article ">
17 pages, 3195 KiB  
Article
Quadratic Non-Linear Optical Properties of the poly(2,5-bis(but-2-ynyloxy) Benzoate Containing the 2-(ethyl(4-((4-nitrophenyl)buta-1,3-diynyl)phenyl)amino)ethanol) Chromophore
by Sandra L. Castañón-Alonso, Omar G. Morales-Saavedra, Marco A. Almaraz-Girón, Sandro Báez-Pimiento, Alejandro Islas-Jácome, L. M. Rocha-Ramírez, Armando Domínguez-Ortiz, Marcos Esparza-Schulz, Adolfo Romero-Galarza and María E. Hernández-Rojas
Polymers 2020, 12(1), 241; https://doi.org/10.3390/polym12010241 - 20 Jan 2020
Cited by 2 | Viewed by 2926
Abstract
Excellent quadratic non-linear optical (ONL-2) properties of the poly(2,5-bis(but-2-ynyloxy) benzoate, containing a polar diacetylene as a chromophore, were found. According with the Maker fringes method, oriented polymer films showing an order parameter of ∼0.23 can display outstanding and stable Second Harmonic [...] Read more.
Excellent quadratic non-linear optical (ONL-2) properties of the poly(2,5-bis(but-2-ynyloxy) benzoate, containing a polar diacetylene as a chromophore, were found. According with the Maker fringes method, oriented polymer films showing an order parameter of ∼0.23 can display outstanding and stable Second Harmonic Generation (SHG) effects under off-resonant conditions (SHG-532 nm). Also, the macroscopic non-linear optical (NLO)-coefficients were evaluated under the rod-like molecular approximation, obtaining: χzzz(2) and χzxx(2) in the order of 280 ± 10 and 100 ± 10 pm V−1, respectively. The mechanical and chemical properties, in addition to the large ONL-2 coefficients exhibited by this polymer, make it a promising organic material in the development of optoelectronic/photonic devices. Full article
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<p>(<b>a</b>) <sup>1</sup>H nuclear magnetic resonance (NMR) spectrum of <b>9</b> in deuterated chloroform (CDCl<sub>3</sub>) and (<b>b</b>) <sup>1</sup>H NMR spectrum of <b>10</b> in TFA-<span class="html-italic">d</span>.</p> Full article ">Figure 2
<p>Experimental and simulated electron paramagnetic resonance (EPR) spectra at room temperature (295 K) of a powder sample of polymer <b>10</b>. Medium wave (MW) Frequency: 9.865 GHz; Mod. Modulation: 100 KHz.</p> Full article ">Figure 3
<p>X-ray diffraction (XRD) pattern of <b>10</b>.</p> Full article ">Figure 4
<p>(<b>a</b>) Polymer thermal properties: Thermogravimetric analysis (TGA)-diagram and (<b>b</b>) thermomechanical analysis (TMA)-diagram.</p> Full article ">Figure 5
<p>2D- and 3D-atomic force microscopy (AFM)-scanned micrographs (same length-scale): (<b>a</b>) A naked indium tin oxide (ITO)-coated glass substrate, (<b>b</b>) an unpoled (BP) polymeric film deposited onto an ITO-substrate and (<b>c</b>) a poled polymeric film sample (AP).</p> Full article ">Figure 6
<p>Ultra Violet (UV)-Visible absorbance spectra of polymeric films: (<b>a</b>) Recorded before and after performing electrical poling (at 120 °C for 5 h), (<b>b</b>) Variations on the absorbance spectra of a poled film after several months (sample was stored at room conditions) and (<b>c</b>) Variations on the absorbance spectra of a poled film after applying a thermally-induced molecular relaxation process (at 80 °C for 30 min and 44 h).</p> Full article ">Figure 7
<p>(<b>a</b>) In-situ Second Harmonic Generation (SHG)-intensity signals recorded at an incident angle of ∼40° (@SHG<sub>MAX,</sub> is the maximum value of the SHG signal al best phase matching conditions) for a polymeric poled film; (<b>b</b>) Averaged SHG-intensity signals and (<b>c</b>) Angle-dependent SHG-signals (Maker fringes).</p> Full article ">Figure 8
<p>Polymer structures containing NLO-coefficients the second order.</p> Full article ">Scheme 1
<p>Synthetic route towards the polymer <b>10</b>.</p> Full article ">
7 pages, 1057 KiB  
Communication
Bacteriostatic Effect of Piezoelectric Poly-3-Hydroxybutyrate and Polyvinylidene Fluoride Polymer Films under Ultrasound Treatment
by Ivan S. Vatlin, Roman V. Chernozem, Alexander S. Timin, Anna P. Chernova, Evgeny V. Plotnikov, Yulia R. Mukhortova, Maria A. Surmeneva and Roman A. Surmenev
Polymers 2020, 12(1), 240; https://doi.org/10.3390/polym12010240 - 20 Jan 2020
Cited by 30 | Viewed by 4858
Abstract
Antibiotic resistance of bacteria stimulates the development of new treatment approaches. Piezoelectric-catalysis has attracted much attention due to the possibility to effectively provide antibacterial effect via generation of reactive oxygen species. However, the influence of the surface charge or potential of a piezopolymer [...] Read more.
Antibiotic resistance of bacteria stimulates the development of new treatment approaches. Piezoelectric-catalysis has attracted much attention due to the possibility to effectively provide antibacterial effect via generation of reactive oxygen species. However, the influence of the surface charge or potential of a piezopolymer on bacteria has not been sufficiently studied so far. This study reports the fabrication and characterization of thin films of piezoelectric polyhydroxybutyrate, polyvinylidene fluoride, and polyvinylidene fluoride trifluoroethylene as well as non-piezoelectric polycaprolactone polymers fabricated using solution casting approach. The piezoelectric coefficient (d33) and surface electric peak-to-peak potential generated by the cyclic mechanical stress applied to the films were measured. Neither any toxic effect of the polymer films nor ultrasound influence on Escherichia coli bacteria behavior is observed. However, significant inhibition of the growth of bacteria is revealed during mechanical stimulation of piezoelectric samples via ultrasound treatment. Thus, this study demonstrates clear bacteriostatic effect of piezoelectric polymers for different tissue engineering applications. Full article
(This article belongs to the Special Issue Bioactive Polymer Scaffolds and Thin Films for Biomedical Applications: State-of-the-Art and Challenges)
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<p>SEM images (upper line) and FTIR spectra (bottom line) of polymer films: (<b>A</b>,<b>D</b>) polycaprolactone (PCL), (<b>B</b>,<b>E</b>) poly(vinylidene fluoride) (PVDF) and (<b>C</b>,<b>F</b>) poly[(R)3-hydroxybutyrate] (PHB).</p> Full article ">Figure 2
<p>Piezoelectric |<span class="html-italic">d</span><sub>33</sub>| charge coefficient and surface electric potential (peak-to-peak).</p> Full article ">Figure 3
<p>(<b>A</b>) Influence of ultrasound on the growth of bacteria: control–bacteria in media, control under U/S–bacteria in media under ultrasound; (<b>B</b>) Influence of the samples on bacteria in static conditions; (<b>C</b>) <span class="html-italic">E. coli</span> growth upon generating piezoelectricity of PVDF, PVDF-TrFE and PHB polymer films. An asterisk (*) denotes a significant statistical difference (<span class="html-italic">p</span> &lt; 0.05) estimated by the one-way analysis of variance (ANOVA) between piezoelectric films and non-piezoactive samples (control and PCL films).</p> Full article ">Figure 4
<p>Colony-forming units (CFU) concentration logarithm obtained in the case of ultrasound treatment for 90 min. Control–bacteria in media under ultrasound. Initial concentration of bacteria was 10<sup>9</sup> CFU. The concentrations of bacteria in the presence of piezomaterials were significantly different from that revealed for control (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">
15 pages, 4095 KiB  
Article
A Robust, Tough and Multifunctional Polyurethane/Tannic Acid Hydrogel Fabricated by Physical-Chemical Dual Crosslinking
by Jie Wen, Xiaopeng Zhang, Mingwang Pan, Jinfeng Yuan, Zhanyu Jia and Lei Zhu
Polymers 2020, 12(1), 239; https://doi.org/10.3390/polym12010239 - 19 Jan 2020
Cited by 44 | Viewed by 7483
Abstract
Commonly synthetic polyethylene glycol polyurethane (PEG–PU) hydrogels possess poor mechanical properties, such as robustness and toughness, which limits their load-bearing application. Hence, it remains a challenge to prepare PEG–PU hydrogels with excellent mechanical properties. Herein, a novel double-crosslinked (DC) PEG–PU hydrogel was fabricated [...] Read more.
Commonly synthetic polyethylene glycol polyurethane (PEG–PU) hydrogels possess poor mechanical properties, such as robustness and toughness, which limits their load-bearing application. Hence, it remains a challenge to prepare PEG–PU hydrogels with excellent mechanical properties. Herein, a novel double-crosslinked (DC) PEG–PU hydrogel was fabricated by combining chemical with physical crosslinking, where trimethylolpropane (TMP) was used as the first chemical crosslinker and polyphenol compound tannic acid (TA) was introduced into the single crosslinked PU network by simple immersion process. The second physical crosslinking was formed by numerous hydrogen bonds between urethane groups of PU and phenol hydroxyl groups in TA, which can endow PEG–PU hydrogel with good mechanical properties, self-recovery and a self-healing capability. The research results indicated that as little as a 30 mg·mL−1 TA solution enhanced the tensile strength and fracture energy of PEG–PU hydrogel from 0.27 to 2.2 MPa, 2.0 to 9.6 KJ·m−2, respectively. Moreover, the DC PEG–PU hydrogel possessed good adhesiveness to diverse substrates because of TA abundant catechol groups. This work shows a simple and versatile method to prepare a multifunctional DC single network PEG–PU hydrogel with excellent mechanical properties, and is expected to facilitate developments in the biomedical field. Full article
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<p>FTIR spectra of TA10–PU(S), TA20–PU(S), and TA30–PU(S) dry gels.</p> Full article ">Figure 2
<p>Water content (<b>A</b>) and tannic acid (TA) content (<b>B</b>) of TAx–PU hydrogels; photos of PU and TAx–PU gels before and after swelling in distilled water (<b>C</b>).</p> Full article ">Figure 3
<p>SEM photographs of lyophilized PU (<b>A</b>) and TA10-PU(S) (<b>B</b>) hydrogels.</p> Full article ">Figure 4
<p>Tensile strain–stress curves of TA–PU hydrogels at as-prepared (<b>A</b>) and swelling equilibrium (<b>B</b>) states. Mechanical properties of pure PU and TA–PU hydrogels: (<b>C</b>) tensile strength; (<b>S</b>) breaking strain; (<b>E</b>) elastic modulus.</p> Full article ">Figure 5
<p>Mooney–Rivlin curves of pure PU and TA–PU hydrogels at as-prepared (<b>A</b>) and swelling equilibrium (<b>B</b>) states.</p> Full article ">Figure 6
<p>Fracture energy of TAx–PU hydrogels at as-prepared and equilibrium swelling states.</p> Full article ">Figure 7
<p>Stress–strain curves from loading–unloading tests (<b>A</b>) and calculated dissipated energy (<b>B</b>) of pure PU and TAx–PU(S) hydrogels under 200% of strain.</p> Full article ">Figure 8
<p>Temperature dependence of the storage modulus, tanδ (<b>A</b>) and loss modulus (<b>B</b>) of TA10(S)–PU, TA20(S)–PU, and TA30(S)–PU gels.</p> Full article ">Figure 9
<p>Tensile loading–unloading cycle curves of TA30–PU(S) hydrogel for different soaking times in distilled water: (<b>A</b>) at strain of 300%; (<b>B</b>) at strain of 600%.</p> Full article ">Figure 10
<p>Adhesive strength of TA30-PU(S) hydrogels compared to stainless steel (SS), poly(methylmethacrylate) (PMMA), titanium (Ti), glass, polycarbonate (PC), tinplate (SPTE), and pork skin tissue.</p> Full article ">Scheme 1
<p>(<b>A</b>) Fabrication procedure of TA–PU hydrogels; (<b>B</b>) chemical structure of TA; (<b>C</b>) the hydrogen bonds between PU and TA.</p> Full article ">
23 pages, 4282 KiB  
Review
Electrospun CNF Supported Ceramics as Electrochemical Catalysts for Water Splitting and Fuel Cell: A Review
by Sahil Verma, Sumit Sinha-Ray and Suman Sinha-Ray
Polymers 2020, 12(1), 238; https://doi.org/10.3390/polym12010238 - 19 Jan 2020
Cited by 49 | Viewed by 7660
Abstract
With the per capita growth of energy demand, there is a significant need for alternative and sustainable energy resources. Efficient electrochemical catalysis will play an important role in sustaining that need, and nanomaterials will play a crucial role, owing to their high surface [...] Read more.
With the per capita growth of energy demand, there is a significant need for alternative and sustainable energy resources. Efficient electrochemical catalysis will play an important role in sustaining that need, and nanomaterials will play a crucial role, owing to their high surface area to volume ratio. Electrospun nanofiber is one of the most promising alternatives for producing such nanostructures. A section of key nano-electrocatalysts comprise of transition metals (TMs) and their derivatives, like oxides, sulfides, phosphides and carbides, etc., as well as their 1D composites with carbonaceous elements, like carbon nanotubes (CNTs) and carbon nanofiber (CNF), to utilize the fruits of TMs’ electronic structure, their inherent catalytic capability and the carbon counterparts’ stability, and electrical conductivity. In this work, we will discuss about such TM derivatives, mostly TM-based ceramics, grown on the CNF substrates via electrospinning. We will discuss about manufacturing methods, and their electrochemical catalysis performances in regards to energy conversion processes, dealing mostly with water splitting, the metal–air battery fuel cell, etc. This review will help to understand the recent evolution, challenges and future scopes related to electrospun transition metal derivative-based CNFs as electrocatalysts. Full article
(This article belongs to the Special Issue Electrospun Nanofibers: Theory and Its Applications)
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<p>Various hydrogen evolution reaction (HER)-active materials with their exchange current density (<span class="html-italic">i</span><sub>0</sub>) vs. hydrogen adsorption free energy (Δ<span class="html-italic">G</span><sub>H*</sub>). Platinum (Pt) and Pt-group materials shows the highest value for HER activity among various materials. Reproduced with permission from Ref. [<a href="#B69-polymers-12-00238" class="html-bibr">69</a>]. Copyright Science 2007.</p> Full article ">Figure 2
<p>Oxygen electrode activities of the nanostructured Mn oxide thin film, nanoparticles of Pt, Ir, and Ru, and the GC substrate. The Mn oxide thin film shows excellent activity for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Reproduced with permission from Ref. [<a href="#B75-polymers-12-00238" class="html-bibr">75</a>]. Copyright, Journal of the American Chemical Society 2010.</p> Full article ">Figure 3
<p>Polarization curve of two different catalysts in the oxygen reduction reaction (ORR) and the essential parameters which are needed for qualitative and quantitative analysis of their performances. Reproduced with permission from Ref. [<a href="#B80-polymers-12-00238" class="html-bibr">80</a>]. Copyright Angewandte Chemie International Edition 2013.</p> Full article ">Figure 4
<p>Schematic of (<b>a</b>) electrospinning and (<b>b</b>) the interaction of polymer and applied electric field is shown. Reproduced with permission from Ref. [<a href="#B84-polymers-12-00238" class="html-bibr">84</a>]. Copyright Springer Nature 2018.</p> Full article ">Figure 5
<p>(<b>a</b>) X-Ray Diffractrogram (XRD) of Nb-CNF-Pt, (<b>b</b>–<b>d</b>) Transmission Electron Microscopy (TEM) images of Nb-CNF-Pt with inset of (<b>d</b>) representing the selected area electron diffraction (SAED) pattern of Nb-CNF-Pt. Reproduced with permission from Ref. [<a href="#B90-polymers-12-00238" class="html-bibr">90</a>]. Copyright, John Wiley and Sons 2019.</p> Full article ">Figure 6
<p>Field Emission Scanning Electron Microscope (FESEM) images of (<b>a</b>) electrospun carbon nanofibers, (<b>b</b>) NF-0.02, (<b>c</b>) NCNF-0.02@Co<sub>3</sub>O<sub>4</sub>-0.2 fiber membranes, and (<b>d</b>) Co<sub>3</sub>O<sub>4</sub> powder. Inset (c) shows a free-standing NCNF-0.02@Co<sub>3</sub>O<sub>4</sub>-0.2 fiber membrane. Reproduced with permission from Ref. [<a href="#B93-polymers-12-00238" class="html-bibr">93</a>]. Copyright Elsevier 2016.</p> Full article ">Figure 7
<p><b>Left</b> hand side: (<b>A</b>) Scanning electron microscopy (SEM) image of pure carbon nanofiber (CNF). (<b>B</b>) SEM image of Co (II)-decorated CNF. (<b>C</b>) Transmission electron microscopy (TEM) image of a single nanofiber of Co (II)-decorated CNF membrane. (<b>D</b>) Raman spectra of set (<b>A</b>) denoted by black line and set (<b>B</b>) denoted by red line with four of the characteristic peaks of crystalline Co<sub>3</sub>O<sub>4</sub> visible in the latter. (<b>E</b>) High resolution X-ray photoelectron spectroscopy (XPS) spectrum of N1s for set (<b>A</b>). (<b>F</b>) Schematic illustration of the different N atoms doped in the carbon matrix. The table indicates the peak positions as well as the atomic % of quaternary and pyridinic nitrogen detected in set (<b>B</b>). In the <b>Right</b> hand side: Electrocatalytic performances of the catalyst Co (II)-decorated CNF. (<b>A</b>) Cyclic Voltammetry (CV) curves of Co (II)-decorated CNF in O<sub>2</sub>-saturated, (denoted by red line) and in N<sub>2</sub>-saturated (denoted by blue line) 0.1 M KOH solution. (<b>B</b>) Linear sweep voltammetry curves of the catalyst as compared to GC and commercial Pt/C for the ORR at electrode rotating speed of 900 rpm. (<b>C</b>) Rotating disk electrode (RDE) curves of the catalyst at various rotating speeds. (<b>D</b>) Koutecky–Levich plots derived from the RDE curves obtained in (<b>C</b>), following Equation (9). (<b>E</b>) Linear sweep voltammetry (LSV) curves of catalyst as compared to GC and commercial Pt/C for the OER at electrode rotating speed of 900 rpm. (<b>F</b>) Tafel slopes of C–CoPAN900 and Pt/C derived from (E). Reproduced with permission from Ref. [<a href="#B99-polymers-12-00238" class="html-bibr">99</a>]. Copyright, Royal Society of Chemistry 2017.</p> Full article ">Figure 8
<p>Schematic of the development of hierarchical meso/macropore structure and graphite edge defects where the potential ORR active sites are formed by water vapor activation. Image (<b>a</b>) shows the I-V curve of glassy carbon RDEs modified with metal-free CNF, vapor-activated metal-free CNF (Act–CNF), as-prepared Fe–CNF, water vapor-activated Fe–CNF for 1 h (Act–Fe–CNF), and commercial 20 wt % Pt/C, measured at a rotation rate of 1600 rpm in O<sub>2</sub>-saturated 0.1 M KOH (aq) solution. Image (<b>b</b>) shows electron transfer number in ORR of Act–Fe–CNF, Fe–CNF, and Pt/C. Reprinted (adapted) with permission from Ref. [<a href="#B107-polymers-12-00238" class="html-bibr">107</a>]. Copyright (2016) American Chemical Society.</p> Full article ">Figure 9
<p>(<b>a</b>) Linear sweep voltammetry (LSV) curves of various catalysts at a rotating speed of 1600 rpm in O<sub>2</sub>-saturated 0.1 M KOH electrolyte. (<b>b</b>) A comparison of the onset and E<sub>1/2</sub> potential from LSV curves. (<b>c</b>) LSV curves of the Fe<sub>3</sub>C/N@Co-doped CNF at increasing rotating speeds (<b>d</b>) Electron transfer numbers of various catalysts in a potential range of 0.5–0.7 V. (<b>e</b>) Schematic illustration of effective 4-electron pathway in Fe<sub>3</sub>C/N@Co-doped CNF. Reproduced with permission from Ref. [<a href="#B109-polymers-12-00238" class="html-bibr">109</a>]. Copyright Elsevier 2018.</p> Full article ">Figure 10
<p>FESEM images showing NiCoP/CNF sample carbonized at 700, 800, 900 °C: (<b>a</b>,<b>b</b>) NiCoP/CNF carbonized at 700 °C, (<b>c</b>,<b>d</b>) NiCoP/CNF carbonized at 800 °C and (<b>e</b>,<b>f</b>) NiCoP/CNF carbonized at 900 °C. Reproduced with permission from Ref. [<a href="#B116-polymers-12-00238" class="html-bibr">116</a>]. Copyright John Wiley and Sons 2018.</p> Full article ">Figure 11
<p>(<b>a</b>) Schematic of the lab-scale, hybrid, water electrolyzer with two asymmetric electrodes, (<b>b</b>) LSV of the device before and after a 70 h durability study, showing practically no change in its catalytic activity, (<b>c</b>) Chronoamperometry of the device for 70 h (inset) shows the supercapacitor assembly with water electrolyzer and (<b>d</b>) Photographic image of the generated O<sub>2</sub> and H<sub>2</sub> bubbles. Reproduced with permission from Ref. [<a href="#B117-polymers-12-00238" class="html-bibr">117</a>]. Copyright Elsevier 2019.</p> Full article ">
14 pages, 16699 KiB  
Article
Multiple Analysis and Characterization of Novel and Environmentally Friendly Feather Protein-Based Wood Preservatives
by Yan Xia, Chengye Ma, Hanmin Wang, Shaoni Sun, Jialong Wen and Runcang Sun
Polymers 2020, 12(1), 237; https://doi.org/10.3390/polym12010237 - 19 Jan 2020
Cited by 9 | Viewed by 3525
Abstract
In this study, feather was used as the source of protein and combined with copper and boron salts to prepare wood preservatives with nano-hydroxyapatite or nano-graphene oxide as nano-carriers. The treatability of preservative formulations, the changes of chemical structure, micromorphology, crystallinity, thermal properties [...] Read more.
In this study, feather was used as the source of protein and combined with copper and boron salts to prepare wood preservatives with nano-hydroxyapatite or nano-graphene oxide as nano-carriers. The treatability of preservative formulations, the changes of chemical structure, micromorphology, crystallinity, thermal properties and chemical composition of wood cell walls during the impregnation and decay experiment were investigated by retention rate of the preservative, Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), thermoanalysis (TG), and confocal Raman microscopy (CRM) techniques. Results revealed that the preservatives (particularly with nano-carrier) successfully penetrated wood blocks, verifying the enhanced effectiveness of protein-based preservative with nano-carrier formulations. Decay experiment demonstrated that the protein-based wood preservative can remarkably improve the decay resistance of the treated wood samples, and it is an effective, environmentally friendly wood preservative. Further analysis of these three preservative groups confirmed the excellent function of nano-hydroxyapatite as a nano-carrier, which can promote the chelation of preservatives with higher content of effective preservatives. Full article
(This article belongs to the Special Issue Advances in Wood Composites II)
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<p>Fourier transform infrared (FTIR) spectrum of wood samples before/after decay.</p> Full article ">Figure 2
<p>SEM images showing the distribution of B, N and Cu within the wood cell wall. (<b>a</b>), control sample, (<b>b</b>), sample treated with P<sub>1</sub>, (<b>c</b>), sample treated with P<sub>2</sub>, (<b>d</b>), sample treated with P<sub>3.</sub></p> Full article ">Figure 3
<p>SEM photographs of wood samples. Cross-section: (<b>a</b>), control sample, (<b>b</b>), sample treated with P<sub>1</sub>, (<b>c</b>), sample treated with P<sub>2</sub>, (<b>d</b>), sample treated with P<sub>3</sub>; Radial-section: (<b>e</b>), control sample, (<b>f</b>), sample treated with P<sub>1</sub>, (<b>g</b>), sample treated with P<sub>2</sub>, (<b>h</b>), sample treated with P<sub>3</sub>.</p> Full article ">Figure 4
<p>SEM photographs of wood samples after 12 weeks decay stage. Cross-section: (<b>a</b>), control sample, (<b>b</b>), sample treated with P<sub>1</sub>, (<b>c</b>), sample treated with P<sub>2</sub>, (<b>d</b>), sample treated with P<sub>3;</sub> Radial-section: (<b>e</b>), control sample, (<b>f</b>), sample treated with P<sub>1</sub>, (<b>g</b>), sample treated with P<sub>2</sub>, (<b>h</b>), sample treated with P<sub>3</sub>.</p> Full article ">Figure 5
<p>X-ray diffraction (XRD) patterns of wood samples before/after decay.</p> Full article ">Figure 6
<p>Thermogravimetric (TG)/Differential Thermogravimetric (DTG) spectrum of wood samples before/after decay.</p> Full article ">Figure 7
<p>Raman images showing the distribution of carbohydrates and lignin.</p> Full article ">Figure 8
<p>Mass loss and weight percent gain (WPG) control and treated samples.</p> Full article ">Scheme 1
<p>The preparation process for the feather protein-based preservative.</p> Full article ">
16 pages, 10548 KiB  
Article
Activated Carbon Microsphere from Sodium Lignosulfonate for Cr(VI) Adsorption Evaluation in Wastewater Treatment
by Keyan Yang, Jingchen Xing, Pingping Xu, Jianmin Chang, Qingfa Zhang and Khan Muhammad Usman
Polymers 2020, 12(1), 236; https://doi.org/10.3390/polym12010236 - 19 Jan 2020
Cited by 25 | Viewed by 4831
Abstract
In this study, activated carbon microsphere (SLACM) was prepared from powdered sodium lignosulfonate (SL) and polystyrene by the Mannich reaction and ZnCl2 activation, which can be used to remove Cr(VI) from the aqueous solution without adding any binder. The SLACM was characterized [...] Read more.
In this study, activated carbon microsphere (SLACM) was prepared from powdered sodium lignosulfonate (SL) and polystyrene by the Mannich reaction and ZnCl2 activation, which can be used to remove Cr(VI) from the aqueous solution without adding any binder. The SLACM was characterized and the batch experiments were conducted under different initial pH values, initial concentrations, contact time durations and temperatures to investigate the adsorption performance of Cr(VI) onto SLACM. The results indicated that the SLACM surface area and average pore size were 769.37 m2/g and 2.46 nm (the mesoporous material), respectively. It was found that the reduced initial pH value, the increased temperature and initial Cr(VI) concentration were beneficial to Cr(VI) adsorption. The maximum adsorption capacity of Cr(VI) on SLACM was 227.7 mg/g at an initial pH value of 2 and the temperature of 40 °C. The adsorption of SLACM for Cr(VI) mainly occurred during the initial stages of the adsorption process. The adsorption kinetic and isotherm experimental data were thoroughly described by Elovich and Langmuir models, respectively. SL could be considered as a potential raw material for the production of activated carbon, which had a considerable potential for the Cr(VI) removal from wastewater. Full article
(This article belongs to the Special Issue Current Trends and Perspectives in the Application of Polymeric Materials for Wastewater Treatment)
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<p>The preparation process diagram of SLACM: (<b>a</b>) Amination of CMPS; (<b>b</b>) Mannich reaction of SL and ACMPS; (<b>c</b>) Activation processes.</p> Full article ">Figure 2
<p>(<b>a</b>) The ARM sample picture; (<b>b</b>) The SLACM sample picture.</p> Full article ">Figure 3
<p>(<b>a</b>,<b>b</b>) SEM images of SLACM surface before Cr(VI) adsorption of 100 and 1 k; (<b>c</b>) SEM image of SLACM fracture surface before Cr(VI) adsorption of 20 k; (<b>d</b>) SEM image of SLACM fracture surface after Cr(VI) adsorption of 20 k; (<b>e</b>,<b>f</b>) TEM images of SLACM before and after Cr(VI) adsorption.</p> Full article ">Figure 4
<p>(<b>a</b>) EDS spectrum of SLACM before Cr(VI) adsorption; (<b>b</b>) EDS spectrum of SLACM after Cr(VI) adsorption; (<b>c–f</b>) EDS elemental mapping patterns of C, N, O and Cr after Cr(VI) adsorption.</p> Full article ">Figure 5
<p>(<b>a</b>) The TG curves of SL, CMPS, ARM and PARM; (<b>b</b>) The DTG curves of SL, CMPS, ARM and PARM.</p> Full article ">Figure 6
<p>(<b>a</b>) The FT-IR spectra of samples; (<b>b</b>) The XRD curves of samples.</p> Full article ">Figure 7
<p>(<b>a</b>) Effect of initial pH on adsorption capacity of SLACM for Cr(VI); (<b>b</b>) Effect of time on adsorption capacity of SLACM for Cr(VI).</p> Full article ">Figure 8
<p>(<b>a</b>) Adsorption isotherm of Cr(VI) onto SLACM and Langmuir isotherm models fitting curves; (<b>b</b>) Adsorption isotherm of Cr(VI) onto SLACM and Freundlich isotherm models fitting curves.</p> Full article ">
14 pages, 3995 KiB  
Article
Enthalpy Relaxation, Crystal Nucleation and Crystal Growth of Biobased Poly(butylene Isophthalate)
by Silvia Quattrosoldi, René Androsch, Andreas Janke, Michelina Soccio and Nadia Lotti
Polymers 2020, 12(1), 235; https://doi.org/10.3390/polym12010235 - 18 Jan 2020
Cited by 21 | Viewed by 4538
Abstract
The crystallization behavior of fully biobased poly(butylene isophthalate) (PBI) has been investigated using calorimetric and microscopic techniques. PBI is an extremely slow crystallizing polymer that leads, after melt-crystallization, to the formation of lamellar crystals and rather large spherulites, due to the low nuclei [...] Read more.
The crystallization behavior of fully biobased poly(butylene isophthalate) (PBI) has been investigated using calorimetric and microscopic techniques. PBI is an extremely slow crystallizing polymer that leads, after melt-crystallization, to the formation of lamellar crystals and rather large spherulites, due to the low nuclei density. Based upon quantitative analysis of the crystal-nucleation behavior at low temperatures near the glass transition, using Tammann’s two-stage nuclei development method, a nucleation pathway for an acceleration of the crystallization process and for tailoring the semicrystalline morphology is provided. Low-temperature annealing close to the glass transition temperature (Tg) leads to the formation of crystal nuclei, which grow to crystals at higher temperatures, and yield a much finer spherulitic superstructure, as obtained after direct melt-crystallization. Similarly to other slowly crystallizing polymers like poly(ethylene terephthalate) or poly(l-lactic acid), low-temperature crystal-nuclei formation at a timescale of hours/days is still too slow to allow non-spherulitic crystallization. The interplay between glass relaxation and crystal nucleation at temperatures slightly below Tg is discussed. Full article
(This article belongs to the Special Issue Polymer Structure and Property)
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Figure 1
<p>Characteristic time of crystallization (<b>a</b>) and spherulite growth rate (<b>b</b>), both as a function of the crystallization temperature. Regarding the characteristic crystallization time, fast scanning chip calorimetry (FSC) and differential scanning calorimetry (DSC) data represent the halftimes and peak-times of crystallization, respectively. In case of DSC data, the error bar is smaller than the symbol size, not shown.</p> Full article ">Figure 2
<p>Temperature–time profile for optical analysis of isothermal nuclei formation in PBI, using Tammann’s two-stage crystal nuclei development method (right). The left part of <a href="#polymers-12-00235-f002" class="html-fig">Figure 2</a> shows selected polarized-light optical microscopy (POM) micrographs of PBI crystallized at 100 °C for 20 min, after nuclei formation at temperatures between 22 °C (bottom row) and 50 °C (top row) for annealing times between 1 min (left column) and 50 min (right column).</p> Full article ">Figure 3
<p>FSC heating curves, heat-flow rate as a function of temperature, of PBI, collected after subjecting PBI to Tammann’s nuclei development method (<b>a</b>). The nucleation temperature was 45 °C and the nucleation time between 1 s (blue) and 10,000 s (red). The growth-stage temperature and time were 85 °C and 1000 s, respectively, and the transfer-heating rate, that is, the rate of heating the system from 45 °C to 85 °C, was 1000 K/s. The inset shows the enthalpy of melting as a function of the nucleation time at 45 °C. The right plot (<b>b</b>) shows the onset time of nuclei formation as a function of temperature.</p> Full article ">Figure 4
<p>POM-images (left, b/w) and atomic force microscopy *AFM)-images (right, colored) of PBI crystallized at 100 °C. The crystallization temperature was approached either directly by cooling the melt (upper row images, hot-crystallization) or by heating the glass after annealing at 22 °C for more than 12 h, to allow nuclei formation (lower-row images, cold-crystallization).</p> Full article ">Figure 5
<p>Sets of FSC heating scans, recorded at a rate of temperature-change of 1000 K/s, of PBI annealed at different temperatures between −20 °C (bottom set of curves) and 25 °C (top set of curves) for different time between 0.001 s (blue) and 10,000 s (red) (<b>a</b>). Before annealing, the sample was cooled from 180 °C, using a rate of 1000 K/s, yielding a fully amorphous sample. Enthalpy of relaxation as a function of the time of annealing at temperatures between 15 and 27.5 °C (<b>b</b>), and between −20 and 15 °C (<b>c</b>).</p> Full article ">Figure 6
<p>Time of completion of enthalpy relaxation (blue), onset time of nuclei formation (gray), and crystallization halftime of PBI (red) as a function of temperature. Crystallization halftimes were determined on direct melt-crystallization (see also <a href="#polymers-12-00235-f001" class="html-fig">Figure 1</a>a, squares and circles) and after prior nuclei formation at 45 °C for different times (star symbol). The nuclei-transfer heating rate, that is, the rate of heating the nuclei from 45 °C to the growth-temperature, was 50 K/min.</p> Full article ">
16 pages, 6884 KiB  
Article
Eudragit: A Novel Carrier for Controlled Drug Delivery in Supercritical Antisolvent Coprecipitation
by Paola Franco and Iolanda De Marco
Polymers 2020, 12(1), 234; https://doi.org/10.3390/polym12010234 - 18 Jan 2020
Cited by 40 | Viewed by 11073
Abstract
In this work, the supercritical antisolvent (SAS) process was used to coprecipitate Eudragit L100-55 (EUD) with diclofenac (DICLO) and theophylline (THEOP), with the aim of obtaining composite microparticles with a prolonged drug release for oral delivery. Working at the optimized conditions in terms [...] Read more.
In this work, the supercritical antisolvent (SAS) process was used to coprecipitate Eudragit L100-55 (EUD) with diclofenac (DICLO) and theophylline (THEOP), with the aim of obtaining composite microparticles with a prolonged drug release for oral delivery. Working at the optimized conditions in terms of pressure and overall concentration in the liquid solution (10.0 MPa and 50 mg/mL), microparticles of EUD/DICLO 20/1 and 10/1 w/w were produced with a mean size of 2.92 µm and 1.53 µm, respectively. For the system EUD/THEOP, well-defined spherical microspheres with a mean diameter ranging from 3.75 µm and 5.93 µm were produced at 12.0 MPa. The produced composite systems were characterized by various techniques, such as scanning electron microscopy, differential scanning calorimetry, X-ray microanalysis, FT-IR and UV–vis spectroscopy. Dissolution studies showed the potential of EUD to prolong the drug release, significantly, up to a few days. Full article
(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Italy (2019,2020))
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<p>A sketch of the supercritical antisolvent (SAS) laboratory plant. S1, tank for the CO<sub>2</sub>; S2, organic solution; RB, refrigerating bath; P1, P2, pumps; V, vessel; M, manometer; TC, thermocouple; MV, micrometric valve; LS, liquid separator; BPV, back-pressure valve; R, rotameter.</p> Full article ">Figure 2
<p>FESEM images of Eudragit particles precipitated from DMSO at 40 °C and 20 mg/mL. Effect of the operating pressure. (<b>a</b>) 9 MPa; (<b>b</b>) 10 MPa; (<b>c</b>) 12 MPa.3.1.2 Effect of polymer concentration in DMSO.</p> Full article ">Figure 3
<p>Volumetric cumulative particle size distributions (PSDs) of EUD precipitated from DMSO at 40 °C and 10 MPa; effect of the polymer concentration in DMSO.</p> Full article ">Figure 4
<p>FESEM images of the drugs precipitated from DMSO at 9 MPa, 40 °C and 20 mg/mL. (<b>a</b>) DICLO; (<b>b</b>) THEOP.</p> Full article ">Figure 5
<p>FESEM images of EUD/DICLO 20/1 particles precipitated from DMSO at 40 °C and 40 mg/mL. Effect of the operating pressure. (<b>a</b>) 9 MPa (run #6); (<b>b</b>) 10 MPa (run #7).</p> Full article ">Figure 6
<p>FESEM images of EUD/THEOP 20/1 powders precipitated from DMSO at 40 °C and 20 mg/mL. Effect of the operating pressure. (<b>a</b>) 10 MPa (run #13) filter; (<b>b</b>) 10 MPa (run #13) precipitating chamber; (<b>c</b>) 12 MPa (run #14); (<b>d</b>) 15 MPa (run #15).</p> Full article ">Figure 7
<p>Volumetric cumulative PSDs of EUD/THEOP 20/1 particles precipitated from DMSO at 40 °C and 20 mg/mL; effect of the operating pressure.</p> Full article ">Figure 8
<p>FESEM images of EUD/DICLO 20/1 particles precipitated from DMSO at 40 °C, 10 MPa. (<b>a</b>) 20 mg/mL (run #8); (<b>b</b>) 50 mg/mL (run #9).</p> Full article ">Figure 9
<p>FESEM images of EUD/THEOP 10/1 <span class="html-italic">w</span>/<span class="html-italic">w</span> precipitated from DMSO at 40 °C, 12 MPa and 40 mg/mL (run #17). (<b>a</b>) Microparticles and (<b>b</b>) expanded microparticles.</p> Full article ">Figure 10
<p>Volumetric cumulative PSDs of EUD/THEOP particles precipitated from DMSO at 40 °C, 12 MPa and 40 mg/mL; effect of the polymer/drug ratio.</p> Full article ">Figure 11
<p>FT-IR spectra for unprocessed and SAS processed Eudragit L100-55, unprocessed drugs, physical mixture polymer/drug and SAS processed Eudragit/drug powders. (<b>a</b>) DICLO; (<b>b</b>) THEOP.</p> Full article ">Figure 12
<p>DSC thermograms of unprocessed and SAS processed EUD, unprocessed drugs, and SAS processed EUD/drug coprecipitated powders. (<b>a</b>) DICLO; (<b>b</b>) THEOP.</p> Full article ">Figure 13
<p>XRD patterns of unprocessed EUD, unprocessed drugs, and SAS processed EUD/drug coprecipitated powders. (<b>a</b>) DICLO; (<b>b</b>) THEOP.</p> Full article ">Figure 14
<p>Dissolution profiles in PBS at 37 °C and pH 7.4. (<b>a</b>) DICLO; (<b>b</b>) THEOP.</p> Full article ">
12 pages, 1990 KiB  
Article
Development of Expanded Takayanagi Model for Tensile Modulus of Carbon Nanotubes Reinforced Nanocomposites Assuming Interphase Regions Surrounding the Dispersed and Networked Nanoparticles
by Yasser Zare and Kyong Yop Rhee
Polymers 2020, 12(1), 233; https://doi.org/10.3390/polym12010233 - 17 Jan 2020
Cited by 12 | Viewed by 3100
Abstract
In this paper, we consider the interphase regions surrounding the dispersed and networked carbon nanotubes (CNT) to develop and simplify the expanded Takayanagi model for tensile modulus of polymer CNT nanocomposites (PCNT). The moduli and volume fractions of dispersed and networked CNT and [...] Read more.
In this paper, we consider the interphase regions surrounding the dispersed and networked carbon nanotubes (CNT) to develop and simplify the expanded Takayanagi model for tensile modulus of polymer CNT nanocomposites (PCNT). The moduli and volume fractions of dispersed and networked CNT and the surrounding interphase regions are considered. Since the modulus of interphase region around the dispersed CNT insignificantly changes the modulus of nanocomposites, this parameter is removed from the developed model. The developed model shows acceptable agreement with the experimental results of several samples. “ER” as nanocomposite modulus per the modulus of neat matrix changes from 1.4 to 7.7 at dissimilar levels of “f” (CNT fraction in the network) and network modulus. Moreover, the lowest relative modulus of 2.2 is observed at the smallest levels of interphase volume fraction ( ϕ i < 0.017), while the highest “ ϕ i ” as 0.07 obtains the highest relative modulus of 11.8. Also, the variation of CNT size (radius and length) significantly changes the relative modulus from 2 to 20. Full article
(This article belongs to the Special Issue Polymer Nanocomposite Interfaces; Fabrication, Properties and Simulations)
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<p>The influences of “<span class="html-italic">E</span><sub>d</sub>” and “<span class="html-italic">E</span><sub>id</sub>” parameters on the predicted modulus (Equation (10)): (<b>a</b>) 3D and (<b>b</b>) contour designs.</p> Full article ">Figure 2
<p>The experimental data of relative modulus and the calculations of original and developed models for (<b>a</b>) chitosan/MWCNT [<a href="#B45-polymers-12-00233" class="html-bibr">45</a>], (<b>b</b>) PP/MWCNT [<a href="#B46-polymers-12-00233" class="html-bibr">46</a>], (<b>c</b>) PVA/MWCNT [<a href="#B47-polymers-12-00233" class="html-bibr">47</a>] and (<b>d</b>) epoxy/MWCNT [<a href="#B17-polymers-12-00233" class="html-bibr">17</a>] samples.</p> Full article ">Figure 3
<p>The effects of “<span class="html-italic">f</span>” and “<span class="html-italic">E</span><sub>N</sub>” parameters on the relative modulus (Equation (11)): (<b>a</b>) 3D and (<b>b</b>) contour plots.</p> Full article ">Figure 4
<p>(<b>a</b>) 3D and (<b>b</b>) contour plots for the effects of “<math display="inline"><semantics> <mrow> <msub> <mi>ϕ</mi> <mi>p</mi> </msub> </mrow> </semantics></math> ” and “<math display="inline"><semantics> <mrow> <msub> <mi>ϕ</mi> <mi>i</mi> </msub> </mrow> </semantics></math>” parameters on the relative modulus.</p> Full article ">Figure 5
<p>The roles of “<span class="html-italic">t</span>” and “<span class="html-italic">E</span><sub>iN</sub>” parameters in the relative modulus according to Equation (11): (<b>a</b>) 3D and (<b>b</b>) contour plots.</p> Full article ">Figure 6
<p>(<b>a</b>) 3D and (<b>b</b>) contour plots for the relative modulus as a function of “<span class="html-italic">R</span>” and “<span class="html-italic">l</span>” parameters.</p> Full article ">
18 pages, 8918 KiB  
Article
Narrowband Spontaneous Emission Amplification from a Conjugated Oligomer Thin Film
by Mohamad S. AlSalhi, Mamduh J. Aljaafreh and Saradh Prasad
Polymers 2020, 12(1), 232; https://doi.org/10.3390/polym12010232 - 17 Jan 2020
Cited by 2 | Viewed by 3594
Abstract
In this paper, we studied the laser and optical properties of conjugated oligomer (CO) 1,4-bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF) thin films, which were cast onto a quartz substrate using a spin coating technique. BECV-DHF was dissolved in chloroform at different concentrations to produce thin films with [...] Read more.
In this paper, we studied the laser and optical properties of conjugated oligomer (CO) 1,4-bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF) thin films, which were cast onto a quartz substrate using a spin coating technique. BECV-DHF was dissolved in chloroform at different concentrations to produce thin films with various thicknesses. The obtained results from the absorption spectrum revealed one sharp peak at 403 nm and two broads at 375 and 428 nm. The photoluminescence (PL) spectra were recorded for different thin films made from different concentrations of the oligomer solution. The threshold, laser-induced fluorescence (LIF), and amplified spontaneous emission (ASE) properties of the CO BECV-DHF thin films were studied in detail. The ASE spectrum was achieved at approximately 482.5 nm at a suitable concentration and sufficient pump energy. The time-resolved spectroscopy of the BECV-DHF films was demonstrated at different pump energies. Full article
(This article belongs to the Special Issue Conjugated Oligomers and Polymer Nanomaterials)
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<p>The molecular structure of 1,4-bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF).</p> Full article ">Figure 2
<p>Laser experimental setup for the CO films.</p> Full article ">Figure 3
<p>Film thickness versus the solution concentration for CO BEVC-DHF deposited by spin coating at 2000 rpm.</p> Full article ">Figure 4
<p>Atomic force microscopy (AFM) images of the oligomer at thicknesses of 270, 88, and 70 nm. (<b>a</b>,<b>c</b>,<b>e</b>) are 3D surface of film with thickness 270, 88 and 70 nm, similarly (<b>b</b>,<b>d</b>,<b>f</b>) are 2D morphology of film with thickness 270, 88 and 70 nm respectively.</p> Full article ">Figure 5
<p>(<b>a</b>–<b>c</b>) SEM images of the oligomer at thicknesses of 70, 88, and 270 nm and speed 3000 rpm. (<b>d</b>–<b>f</b>) SEM images of the oligomer at thicknesses of 95,127, and 380 nm and speed 2000 rpm.</p> Full article ">Figure 5 Cont.
<p>(<b>a</b>–<b>c</b>) SEM images of the oligomer at thicknesses of 70, 88, and 270 nm and speed 3000 rpm. (<b>d</b>–<b>f</b>) SEM images of the oligomer at thicknesses of 95,127, and 380 nm and speed 2000 rpm.</p> Full article ">Figure 6
<p>Absorption spectra of the CO BEVC-DHF samples with different thicknesses (380 nm, 127 nm, and 95 nm).</p> Full article ">Figure 7
<p>Photoluminescence (PL) spectra for different film thicknesses (380, 127 and 90 nm).</p> Full article ">Figure 8
<p>Change in transmission versus wavelength first-order derivatives of the transmission concerning the wavelength.</p> Full article ">Figure 9
<p>Optical energy gap by crossing the absorption and fluorescence spectra of the CO thin film. The black and brown curves are normalized absorption and fluorescence spectra, the area fill with brown color indicates the spectral overlap between the absorption and fluorescence spectra, attributed to V0 (0-0) band.</p> Full article ">Figure 10
<p>Amplified spontaneous emission (ASE), threshold, and laser-induced fluorescence (LIF) spectra of the CO film with a thickness of 380 nm and a concentration of 15 mg/mL. The <a href="#polymers-12-00232-f010" class="html-fig">Figure 10</a> also shows deconvolution (DeCon) of LIF spectra, where the light green (A), Pink (B), sky blue (C) and violet (D) bands are ascribed to V0, V1, V2 and dimer bands.</p> Full article ">Figure 11
<p>Relationship between the pump energy, intensity, and FWHM of the ASE of the CO film with a thickness of 380 nm and a concentration of 15 mg/mL. The green line indicates the ASE intensity (a.u.) and brown line indicates FWHM (nm).</p> Full article ">Figure 12
<p>Time dynamics of CO thin-film LIF in chloroform at a pump energy of 0.55 mJ and a concentration of 15 mg/mL. The subfigure is the Z slice at 483 nm, which gives the intensity (a.u) vs time (ns) profile of the LIF peak at approximately 485 nm.</p> Full article ">Figure 13
<p>Time dynamics of the CO thin film (<b>a</b>) threshold (<b>b</b>) time profile of threshold in chloroform at pump energy of 0.65 mJ and a concentration of 15 mg/mL.</p> Full article ">Figure 13 Cont.
<p>Time dynamics of the CO thin film (<b>a</b>) threshold (<b>b</b>) time profile of threshold in chloroform at pump energy of 0.65 mJ and a concentration of 15 mg/mL.</p> Full article ">Figure 14
<p>Time dynamics of CO in chloroform at pump energy of 3 mJ and a concentration of 15 mg/mL. The subfigure is the Z slice at 482 nm, which gives the intensity (a.u) vs time (ns) profile of the ASE peak at 482.5 nm.</p> Full article ">Figure 15
<p>Time dynamics of the CO thin film at 15 mg/mL and at a high pump energy (5 mJ). The subfigure is the Z slice at 487 nm, which gives the intensity (a.u) vs time (ns) profile of the ASE peak at approximately 483 nm.</p> Full article ">Figure 16
<p>ASE stability of CO films with different thickness at different speed (<b>a</b>) 2000rpm and (<b>b</b>) 3000 rpm with 250 pulse and energy 2.5 mJ.</p> Full article ">Figure 17
<p>Waveguiding nature of the CO thin films for (<b>a</b>) 2000 rpm and (<b>b</b>) 3000 rpm. The green shapes in <a href="#polymers-12-00232-f017" class="html-fig">Figure 17</a>a represent different oligomer crystal structures (for 2000 rpm) and green wave in <a href="#polymers-12-00232-f017" class="html-fig">Figure 17</a>b represents amorphous structure. The blue shapes with in the film represent the grain boundaries. The blue cone or triangle in <a href="#polymers-12-00232-f017" class="html-fig">Figure 17</a>a,b represents the ASE beam.</p> Full article ">
16 pages, 3763 KiB  
Article
Poly(d,l-Lactic acid) Composite Foams Containing Phosphate Glass Particles Produced via Solid-State Foaming Using CO2 for Bone Tissue Engineering Applications
by Maziar Shah Mohammadi, Ehsan Rezabeigi, Jason Bertram, Benedetto Marelli, Richard Gendron, Showan N. Nazhat and Martin N. Bureau
Polymers 2020, 12(1), 231; https://doi.org/10.3390/polym12010231 - 17 Jan 2020
Cited by 13 | Viewed by 3806
Abstract
This study reports on the production and characterization of highly porous (up to 91%) composite foams for potential bone tissue engineering (BTE) applications. A calcium phosphate-based glass particulate (PGP) filler of the formulation 50P2O5-40CaO-10TiO2 mol.%, was incorporated into [...] Read more.
This study reports on the production and characterization of highly porous (up to 91%) composite foams for potential bone tissue engineering (BTE) applications. A calcium phosphate-based glass particulate (PGP) filler of the formulation 50P2O5-40CaO-10TiO2 mol.%, was incorporated into biodegradable poly(d,l-lactic acid) (PDLLA) at 5, 10, 20, and 30 vol.%. The composites were fabricated by melt compounding (extrusion) and compression molding, and converted into porous structures through solid-state foaming (SSF) using high-pressure gaseous carbon dioxide. The morphological and mechanical properties of neat PDLLA and composites in both nonporous and porous states were examined. Scanning electron microscopy micrographs showed that the PGPs were well dispersed throughout the matrices. The highly porous composite systems exhibited improved compressive strength and Young’s modulus (up to >2-fold) and well-interconnected macropores (up to ~78% open pores at 30 vol.% PGP) compared to those of the neat PDLLA foam. The pore size of the composite foams decreased with increasing PGPs content from an average of 920 µm for neat PDLLA foam to 190 µm for PDLLA-30PGP. Furthermore, the experimental data was in line with the Gibson and Ashby model, and effective microstructural changes were confirmed to occur upon 30 vol.% PGP incorporation. Interestingly, the SSF technique allowed for a high incorporation of bioactive particles (up to 30 vol.%—equivalent to ~46 wt.%) while maintaining the morphological and mechanical criteria required for BTE scaffolds. Based on the results, the SSF technique can offer more advantages and flexibility for designing composite foams with tunable characteristics compared to other methods used for the fabrication of BTE scaffolds. Full article
(This article belongs to the Special Issue Polyester-Based Eco-Composites)
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<p>Scanning electron microscopy (SEM) micrographs of PDLLA-PGP composite monoliths (nonporous) with different PGP contents and magnifications: (<b>a</b>) PDLLA-5PGP (50×), (<b>b</b>) PDLLA-10PGP (50×), (<b>c</b>) PDLLA-20PGP (50×), (<b>d</b>) PDLLA-30PGP (50×), (<b>e</b>) PDLLA-20PGP (500×), and (<b>f</b>) PDLLA-30PGP (500×). The arrows indicate the glass particles (PGP).</p> Full article ">Figure 2
<p>Mechanical properties of neat PDLLA and PDLLA-PGP composite monoliths (nonporous). (<b>a</b>) Flexural strength, (<b>b</b>) Young’s modulus. * Statistically significant compared to PDLLA (<span class="html-italic">p</span> &lt; 0.05); Δ statistically significant compared to previous material (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 3
<p>SEM micrographs of the neat and composite foams. (<b>a</b>) PDLLA, (<b>b</b>) PDLLA-5PGP, (<b>c</b>) PDLLA-10PGP, (<b>d</b>) PDLLA-20PGP, (<b>e</b>) PDLLA-20PGP at higher magnification, (<b>f</b>) PDLLA-30PGP, (<b>g</b>) PDLLA-30PGP at higher magnification, (<b>h</b>) PDLLA-PGP composite foam showing the presence of a PGP in the pore wall, creating pore wall rupture during foam expansion.</p> Full article ">Figure 4
<p>Micro-CT images of the SSF fabricated foams. (<b>a</b>) PDLLA, (<b>b</b>) PDLLA-5PGP, (<b>c</b>) PDLLA-10PGP, (<b>d</b>) PDLLA-20PGP, (<b>e</b>) PDLLA-30PGP. Note that, i and ii represent 2D and 3D images, respectively. The scale bars of the images on the left and right columns are 3 mm and 2 mm, respectively.</p> Full article ">Figure 5
<p>Open pore content and nucleation density of PDLLA-PGP composite foams. (<b>a</b>) Dependency of the percentage of open pores on PGP content, (<b>b</b>) nucleation density versus PGP content for PDLLA-PGP composite foams with different PGP content.</p> Full article ">Figure 6
<p>Mechanical properties of neat PDLLA and PDLLA-PGP composite foams. (<b>a</b>) Compressive strength, (<b>b</b>) Young’s modulus. * Statistically significant compared to PDLLA (<span class="html-italic">p</span> &lt; 0.05); Δ statistically significant compared to previous material (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">
20 pages, 4177 KiB  
Article
Nanolayers of Poly(N,N′-Dimethylaminoethyl Methacrylate) with a Star Topology and Their Antibacterial Activity
by Paulina Teper, Joanna Chojniak-Gronek, Anna Hercog, Natalia Oleszko-Torbus, Grażyna Płaza, Jerzy Kubacki, Katarzyna Balin, Agnieszka Kowalczuk and Barbara Mendrek
Polymers 2020, 12(1), 230; https://doi.org/10.3390/polym12010230 - 17 Jan 2020
Cited by 18 | Viewed by 4103
Abstract
In this paper, we focus on the synthesis and characterization of novel stable nanolayers made of star methacrylate polymers. The effect of nanolayer modification on its antibacterial properties was also studied. A covalent immobilization of star poly(N,N′-dimethylaminoethyl methacrylate) (PDMAEMA) [...] Read more.
In this paper, we focus on the synthesis and characterization of novel stable nanolayers made of star methacrylate polymers. The effect of nanolayer modification on its antibacterial properties was also studied. A covalent immobilization of star poly(N,N′-dimethylaminoethyl methacrylate) (PDMAEMA) to benzophenone functionalized glass or silicon supports was carried out via a “grafting to” approach using UV irradiation. To date, star polymer UV immobilization has never been used for this purpose. The thickness of the resulting nanolayers increased from 30 to 120 nm with the molar mass of the immobilized stars. The successful bonding of star PDMAEMA to the supports was confirmed by surface sensitive quantitative spectroscopic methods. Next, amino groups in the polymer layer were quaternized with bromoethane, and the influence of this modification on the antibacterial properties of the obtained materials was analyzed using a selected reference strain of bacteria. The resulting star nanolayer surfaces exhibited higher antimicrobial activity against Bacillus subtilis ATCC 6633 compared to that of the linear PDMAEMA analogues grafted onto a support. These promising results and the knowledge about the influence of the topology and modification of PDMAEMA layers on their properties may help in searching for new materials for antimicrobial applications in medicine. Full article
(This article belongs to the Special Issue Topology Effects on Polymer Properties)
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<p>Atomic force microscopy images: (<b>A</b>) bare wafer with -OH group, (<b>B</b>) wafer with benzophenone derivative, (<b>C</b>) wafer with immobilized linear PDMAEMA (sample L3, <a href="#polymers-12-00230-t001" class="html-table">Table 1</a>), and (<b>D</b>) wafer with immobilized star PDMAEMA (sample G3, <a href="#polymers-12-00230-t001" class="html-table">Table 1</a>).</p> Full article ">Figure 2
<p>XPS survey spectra of (<b>A</b>) the OH terminated surface, (<b>B</b>) the BPH terminated surface, (<b>C</b>) the star polymer layer (SG3, <a href="#polymers-12-00230-t002" class="html-table">Table 2</a>), and (<b>D</b>) the linear polymer layer (SL3, <a href="#polymers-12-00230-t002" class="html-table">Table 2</a>).</p> Full article ">Figure 3
<p>The deconvoluted lines of XPS spectra: (<b>A</b>) the C 1s core level of the star polymer layer, (<b>B</b>) the N 1s core level of the star polymer layer (sample SG3, <a href="#polymers-12-00230-t002" class="html-table">Table 2</a>), (<b>C</b>) the C 1s core level of the linear polymer layer, and (<b>D</b>) the N 1s core level of the linear polymer layer (sample SL3, <a href="#polymers-12-00230-t002" class="html-table">Table 2</a>).</p> Full article ">Figure 4
<p>Mass spectra of the SG3 (red) and SL3 (blue) samples collected in positive polarity. The intensity scale of mass spectra of the SL3 sample is reversed for easier comparison of the intensities of a particular ion.</p> Full article ">Figure 5
<p>Distribution maps of selected ions obtained from the 300 × 300 μm areas for the SG3 (first line) and SL3 nanolayers (second line). The intensity scale of distribution maps was unified within a particular ion.</p> Full article ">Figure 6
<p>XPS spectra of the QPDMAEMA nanolayers: (<b>A</b>) survey spectra and (<b>B</b>) the N 1s core level of the linear QPDMAEMA nanolayer (sample QSL4, <a href="#polymers-12-00230-t004" class="html-table">Table 4</a>); (<b>C</b>) survey spectra and (<b>D</b>) the N 1s core level of the star QPDMAEMA nanolayer (samples QSG4, <a href="#polymers-12-00230-t004" class="html-table">Table 4</a>).</p> Full article ">Figure 7
<p>SEM microscopy images of quaternized PDMAEMA nanolayers after 24 h of exposure to bacteria with visible bacterial cells: (<b>A</b>,<b>B</b>) star nanolayers (sample QSG4, <a href="#polymers-12-00230-t005" class="html-table">Table 5</a>); (<b>C</b>,<b>D</b>) linear nanolayers (sample QSL4, <a href="#polymers-12-00230-t005" class="html-table">Table 5</a>).</p> Full article ">Scheme 1
<p>Preparation of the star polymer layers. (<b>A</b>) Synthesis of star polymers via the “core-first” method. (<b>B</b>) Immobilization of the polymer on the solid support. ATRP, atom transfer radical polymerization.</p> Full article ">Scheme 2
<p>The preparation of quaternized PDMAEMA nanolayers.</p> Full article ">
15 pages, 2640 KiB  
Article
New Eco-Friendly Synthesized Thermosets from Isoeugenol-Based Epoxy Resins
by Quentin Ruiz, Sylvie Pourchet, Vincent Placet, Laurent Plasseraud and Gilles Boni
Polymers 2020, 12(1), 229; https://doi.org/10.3390/polym12010229 - 17 Jan 2020
Cited by 24 | Viewed by 5196
Abstract
Epoxy resin plays a key role in composite matrices and DGEBA is the major precursor used. With the aim of favouring the use of bio resources, epoxy resins can be prepared from lignin. In particular, diglycidyl ether of isoeugenol derivatives are good candidates [...] Read more.
Epoxy resin plays a key role in composite matrices and DGEBA is the major precursor used. With the aim of favouring the use of bio resources, epoxy resins can be prepared from lignin. In particular, diglycidyl ether of isoeugenol derivatives are good candidates for the replacement of DGEBA. This article presents an effective and eco-friendly way to prepare epoxy resin derived from isoeugenol (BioIgenox), making its upscale possible. BioIgenox has been totally characterized by NMR, FTIR, MS and elemental analyses. Curing of BioIgenox and camphoric anhydride with varying epoxide function/anhydride molar ratios has allowed determining an optimum ratio near 1/0.9 based on DMA and DSC analyses and swelling behaviours. This thermoset exhibits a Tg measured by DMA of 165 °C, a tensile storage modulus at 40 °C of 2.2 GPa and mean 3-point bending stiffness, strength and strain at failure of 3.2 GPa, 120 MPa and 6.6%, respectively. Transposed to BioIgenox/hexahydrophtalic anhydride, this optimized formulation gives a thermoset with a Tg determined by DMA of 140 °C and a storage modulus at 40 °C of 2.6 GPa. The thermal and mechanical properties of these two thermosets are consistent with their use as matrices for structural or semi-structural composites. Full article
(This article belongs to the Special Issue Thermosets II)
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<p>Thermograms of dynamic curing reaction of thermoset series with varying Epoxide function/CA ratios.</p> Full article ">Figure 2
<p>Curing of BioIgenox using CA or HHPA as a hardener.</p> Full article ">Figure 3
<p>Effect of the epoxide function/CA ratio on the glass transition determined by DSC.</p> Full article ">Figure 4
<p>Storage modulus (<b>a</b>), loss modulus (<b>b</b>), loss factor (<b>c</b>) and Cole–Cole diagram (<b>d</b>) for ep/CA/DMIA (1/X/0.025) formulation with X = 1 (black), 0.9 (green), 0.8 (blue), 0.7 (red), 0.6 (yellow), 0.5 (grey).</p> Full article ">Figure 5
<p>3-point bending curves for three tested specimens. Maximum bending stress vs.; strain (ep/CA/DMID 1/0.8/0.025).</p> Full article ">Figure 6
<p>Thermograms comparison for HHPA or CA cured epoxy thermoset (ep/CA/DMID 1/0.9/0.025).</p> Full article ">Scheme 1
<p>Molecular representations of reagents used in the resin manufacturing process. Left: Epoxy monomer precursors: BioIgenol (Glycidylether isoeugenol (GEiE), di isoeugenol propanol (DiEP1/DiEP2)). Center BioIgenox (Glycidylether epoxy isoeugenol (GEEpiE), di epoxy isoeugenol propanol (DiEpiE1/DiEpiE2)). Right: Anhydride hardeners: camphoric anhydride (CA), hexahydrophtalic anhydride (HHPA), catalyst: 1,2-dimethylimidazole (DMID).</p> Full article ">Scheme 2
<p>Synthetic pathway leading to BioIgenox from isoeugenol.</p> Full article ">Scheme 3
<p>Molecular representation of BioIgenol.</p> Full article ">Scheme 4
<p>Molecular representation of BioIgenox.</p> Full article ">Scheme 5
<p>Mechanism leading to the DiEP1/DiEP2 formation.</p> Full article ">
12 pages, 3023 KiB  
Article
Poly(ε-Caprolactone)/Poly(Lactic Acid) Blends Compatibilized by Peroxide Initiators: Comparison of Two Strategies
by Marta Przybysz-Romatowska, Józef Haponiuk and Krzysztof Formela
Polymers 2020, 12(1), 228; https://doi.org/10.3390/polym12010228 - 16 Jan 2020
Cited by 46 | Viewed by 6087
Abstract
Poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) blends were compatibilized by reactive blending and by copolymers formed during reaction in the solution. The reactive blending of PCL/PLA was performed using di-(2-tert-butyl-peroxyisopropyl)benzene (BIB) or dicumyl peroxide (DCP) as radical initiator. PCL-g-PLA copolymers were [...] Read more.
Poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) blends were compatibilized by reactive blending and by copolymers formed during reaction in the solution. The reactive blending of PCL/PLA was performed using di-(2-tert-butyl-peroxyisopropyl)benzene (BIB) or dicumyl peroxide (DCP) as radical initiator. PCL-g-PLA copolymers were prepared using 1.0 wt. % of DCP or BIB via reaction in solution, which was investigated through a Fourier transform infrared spectrometry (FTIR) and nuclear magnetic resonance (NMR) in order to better understand the occurring mechanisms. The effect of different additions such as PCL-g-PLA copolymers, DCP, or BIB on the properties of PCL/PLA blends was studied. The unmodified PCL/PLA blends showed a sea-island morphology typical of incompatible blends, where PLA droplets were dispersed in the PCL matrix. Application of organic peroxides improved miscibility between PCL and PLA phases. A similar effect was observed for PCL/PLA blend compatibilized by PCL-g-PLA copolymer, where BIB was used as initiator. However, in case of application of the peroxides, the PCL/PLA blends were cross-linked, and it has been confirmed by the gel fraction and melt flow index measurements. The thermal and mechanical properties of the blends were also investigated by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and tensile strength. Full article
(This article belongs to the Special Issue Environmentally-Friendly Polymeric Materials Based on Recycling and Bio-Based Components)
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<p>FTIR absorption spectra of neat PCL and PLA, and PCL-<span class="html-italic">g</span>-PLA copolymers.</p> Full article ">Figure 2
<p><sup>1</sup>H NMR spectra of neat PCL and PLA, and PCL-<span class="html-italic">g</span>-PLA copolymers.</p> Full article ">Figure 3
<p>SEM images of PCL/PLA blend (75/25), and PCL/PLA blends compatibilized by copolymers and DCP or BIB in reactive blending.</p> Full article ">Figure 4
<p>Results of TGA thermograms for PCL/PLA blends.</p> Full article ">Figure 5
<p>DSC second heating curves (<b>A</b>) and DSC cooling curves (<b>B</b>) of PCL/PLA blends.</p> Full article ">Figure 6
<p>Storage (<b>A</b>) and Loss (<b>B</b>) Modulus of PCL/PLA blends.</p> Full article ">Figure 7
<p>Representative stress-strain curves of studied PCL/PLA blends.</p> Full article ">Scheme 1
<p>Likely reaction pathway for the cross-linking or grafting reaction of PCL and PLA in the presence of the free-radical initiator.</p> Full article ">
2 pages, 156 KiB  
Correction
Correction: Duan, G.J., et al. The Poly(acrylonitrule-co-acrylic acid)-graft-β-cyclodextrin Hydrogel for Thorium(IV) Adsorption. Polymers 2017, 9, 201
by Guojian Duan, Qiangqiang Zhong, Lei Bi, Liu Yang, Tonghuan Liu, Xiaoning Shi and Wangsuo Wu
Polymers 2020, 12(1), 227; https://doi.org/10.3390/polym12010227 - 16 Jan 2020
Viewed by 2418
Abstract
The authors wish to make the following corrections to their paper [...] Full article
(This article belongs to the Special Issue Electroactive Polymers and Gels)
17 pages, 2855 KiB  
Article
A Deeper Microscopic Study of the Interaction between Gum Rosin Derivatives and a Mater-Bi Type Bioplastic
by Miguel Aldas, Emilio Rayón, Juan López-Martínez and Marina P. Arrieta
Polymers 2020, 12(1), 226; https://doi.org/10.3390/polym12010226 - 16 Jan 2020
Cited by 34 | Viewed by 10749
Abstract
The interaction between gum rosin and gum rosin derivatives with Mater-Bi type bioplastic, a biodegradable and compostable commercial bioplastic, were studied. Gum rosin and two pentaerythritol esters of gum rosin (Lurefor 125 resin and Unik Tack P100 resin) were assessed as sustainable compatibilizers [...] Read more.
The interaction between gum rosin and gum rosin derivatives with Mater-Bi type bioplastic, a biodegradable and compostable commercial bioplastic, were studied. Gum rosin and two pentaerythritol esters of gum rosin (Lurefor 125 resin and Unik Tack P100 resin) were assessed as sustainable compatibilizers for the components of Mater-Bi® NF 866 polymeric matrix. To study the influence of each additive in the polymeric matrix, each gum rosin-based additive was compounded in 15 wt % by melt-extrusion and further injection molding process. Then, the mechanical properties were assessed, and the tensile properties and impact resistance were determined. Microscopic analyses were carried out by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and atomic force microscopy with nanomechanical assessment (AFM-QNM). The oxygen barrier and wettability properties were also assayed. The study revealed that the commercial thermoplastic starch is mainly composed of three phases: A polybutylene adipate-co-terephthalate (PBAT) phase, an amorphous phase of thermoplastic starch (TPSa), and a semi-crystalline phase of thermoplastic starch (TPSc). The poor miscibility among the components of the Mater-Bi type bioplastic was confirmed. Finally, the formulations with the gum rosin and its derivatives showed an improvement of the miscibility and the solubility of the components depending on the additive used. Full article
(This article belongs to the Special Issue Sustainable Bio-Based Polymers: Towards a Circular Bioeconomy)
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Full article ">Figure 1
<p>Mechanical properties of the Mater-Bi<sup>®</sup> NF 866, Mater-Bi<sup>®</sup> NF 866 with Luerefor 125 resin, Mater-Bi<sup>®</sup> NF 866 with Unik Tack P100 resin, and Mater-Bi<sup>®</sup> NF 866 with gum rosin: Young’s modulus and tensile strength (<b>a</b>) and elongation at break and Charpy’s impact energy (<b>b</b>). <sup>a–d</sup> Different letters within the same property indicate statistically significant differences between formulations (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 2
<p>Dynamic thermo-mechanical analysis (DTMA) curves of the loss factor (<b>a</b>,<b>b</b>) and the storage modulus (<b>c</b>,<b>d</b>) of Mater-Bi<sup>®</sup> NF 866, Mater-Bi<sup>®</sup> NF 866 with Luerefor 125 resin, Mater-Bi<sup>®</sup> NF 866 with Unik Tack P100 resin, and Mater-Bi<sup>®</sup> NF 866 with gum rosin. The main transition temperatures are specified.</p> Full article ">Figure 3
<p>Colored field emission scanning electron microscopy (FESEM) images acquired at two magnifications on: Mater-Bi<sup>®</sup> NF 866 (<b>a</b>,<b>a’</b>), Mater-Bi<sup>®</sup> NF 866 with Luerefor 125 resin (<b>b</b>,<b>b’</b>), Mater-Bi<sup>®</sup> NF 866 with Unik Tack P100 resin (<b>c</b>,<b>c’</b>), and Mater-Bi<sup>®</sup> NF 866 with gum rosin (<b>d</b>,<b>d’</b>).</p> Full article ">Figure 4
<p>Peak Force-error channel assessed by atomic force microscopy (AFM) of Mater-Bi<sup>®</sup> NF 866 with (I) PBAT free of PCL and (II) PCL particles in PBAT phase (<b>a</b>,<b>a’</b>); Mater-Bi<sup>®</sup> NF 866 with Luerefor 125 resin (<b>b</b>), Mater-Bi<sup>®</sup> NF 866 with Unik Tack P100 resin (<b>c</b>), and Mater-Bi<sup>®</sup> NF 866 with gum rosin (<b>d</b>).</p> Full article ">Figure 5
<p>Force adhesion map acquired by atomic force microscopy with nanomechanical assessment (AFM-QNM) on supplied Mater-Bi<sup>®</sup> NF 866.</p> Full article ">Figure 6
<p>Elastic modulus map obtained by AFM-QNM of Mater-Bi<sup>®</sup> NF 866 (<b>a</b>,<b>a’</b>); Mater-Bi<sup>®</sup> NF 866 with Luerefor 125 resin (<b>b</b>), Mater-Bi<sup>®</sup> NF 866 with Unik Tack P100 resin (<b>c</b>), and Mater-Bi<sup>®</sup> NF 866 with gum rosin (<b>d</b>).</p> Full article ">
21 pages, 5948 KiB  
Article
Sustainable Plastics from Biomass: Blends of Polyesters Based on 2,5-Furandicarboxylic Acid
by Niki Poulopoulou, Dimitra Smyrnioti, George N. Nikolaidis, Ilektra Tsitsimaka, Evi Christodoulou, Dimitrios N. Bikiaris, Maria Anna Charitopoulou, Dimitris S. Achilias, Maria Kapnisti and George Z. Papageorgiou
Polymers 2020, 12(1), 225; https://doi.org/10.3390/polym12010225 - 16 Jan 2020
Cited by 38 | Viewed by 7136
Abstract
Intending to expand the thermo-physical properties of bio-based polymers, furan-based thermoplastic polyesters were synthesized following the melt polycondensation method. The resulting polymers, namely, poly(ethylene 2,5-furandicarboxylate) (PEF), poly(propylene 2,5-furandicarboxylate) (PPF), poly(butylene 2,5-furandicarboxylate) (PBF) and poly(1,4-cyclohexanedimethylene 2,5-furandicarboxylate) (PCHDMF) are used in blends together with various [...] Read more.
Intending to expand the thermo-physical properties of bio-based polymers, furan-based thermoplastic polyesters were synthesized following the melt polycondensation method. The resulting polymers, namely, poly(ethylene 2,5-furandicarboxylate) (PEF), poly(propylene 2,5-furandicarboxylate) (PPF), poly(butylene 2,5-furandicarboxylate) (PBF) and poly(1,4-cyclohexanedimethylene 2,5-furandicarboxylate) (PCHDMF) are used in blends together with various polymers of industrial importance, including poly(ethylene terephthalate) (PET), poly(ethylene 2,6-naphthalate) (PEN), poly(L-lactic acid) (PLA) and polycarbonate (PC). The blends are studied concerning their miscibility, crystallization and solid-state characteristics by using wide-angle X-ray diffractometry (WAXD), differential scanning calorimetry (DSC) and polarized light microscopy (PLM). PEF blends show in general dual glass transitions in the DSC heating traces for the melt quenched samples. Only PPF–PEF blends show a single glass transition and a single melt phase in PLM. PPF forms immiscible blends except with PEF and PBF. PBF forms miscible blends with PCHDMF and PPF, whereas all other blends show dual glass transitions in DSC and phase separation in PLM. PCHDMF–PEF and PEN–PEF blends show two glass transition temperatures, but they shift to intermediate temperature values depending on the composition, indicating some partial miscibility of the polymer pairs. Full article
(This article belongs to the Special Issue Biobased and Biodegradable Polymers)
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<p>(<b>a</b>) WAXD patterns for as received PEN–PEF blends, (<b>b</b>) DSC heating thermograms, (<b>c</b>) details of DSC thermograms in the T<sub>g</sub> region and (<b>d</b>) derivative heat flow for melt-quenched PEN–PEF blend samples.</p> Full article ">Figure 2
<p>(<b>a</b>) WAXD patterns for as received PC–PEF blends, (<b>b</b>) DSC heating thermograms, and (<b>c</b>) derivative heat flow for melt-quenched PEN–PEF blend samples and (<b>d</b>) FTIR spectra of neat PC, PEF and their blend.</p> Full article ">Figure 3
<p>(<b>a</b>) WAXD patterns for as received PL–PEF blends, (<b>b</b>) DSC heating thermograms for melt- quenched PLA–PEF blend samples, (<b>c</b>) derivative heat flow for melt-quenched PLA–PEF blend samples and (<b>d</b>) FTIR spectra of neat PLA, PEF and their blends.</p> Full article ">Figure 4
<p>(<b>a</b>) WAXD patterns for as received PCHDMF–PEF blends, (<b>b</b>) DSC heating thermograms, (<b>c</b>) details of DSC thermograms in the T<sub>g</sub> region and (<b>d</b>) derivative heat flow for melt-quenched PCHDMF–PEF blend samples.</p> Full article ">Figure 5
<p>(<b>a</b>) DSC heating thermograms, (<b>b</b>) details of DSC thermograms in the T<sub>g</sub> region, and (<b>c</b>) derivative heat flow for melt-quenched PEF blend samples with various polymers and 50-50 composition.</p> Full article ">Figure 6
<p>PLM photographs showing the melt phase of 50-50 blends: (<b>a</b>) PC–PEF, (<b>b</b>) PEN-–PEF, (<b>c</b>) PET–PEF, (<b>d</b>) PCHDMF-–PEF, (<b>e</b>) PLA–PEF, (<b>f</b>) PPF–PEF, (<b>g</b>) PBF–PEF, (<b>h</b>) PBF–PPF, (<b>i</b>) PPT–PPF, (<b>j</b>) PCHDMF–PPF.</p> Full article ">Figure 6 Cont.
<p>PLM photographs showing the melt phase of 50-50 blends: (<b>a</b>) PC–PEF, (<b>b</b>) PEN-–PEF, (<b>c</b>) PET–PEF, (<b>d</b>) PCHDMF-–PEF, (<b>e</b>) PLA–PEF, (<b>f</b>) PPF–PEF, (<b>g</b>) PBF–PEF, (<b>h</b>) PBF–PPF, (<b>i</b>) PPT–PPF, (<b>j</b>) PCHDMF–PPF.</p> Full article ">Figure 7
<p>SEM photographs showing the melt-quenched samples of 50-50 blends: (<b>a</b>) PC–PEF, (<b>b</b>) PEN–PEF, (<b>c</b>) PET–PEF, (<b>d</b>) PCHDMF–PEF, (<b>e</b>) PLA–PEF, (<b>f)</b> PPF–PEF, (<b>g</b>) PBF–PEF, (<b>h</b>) PBF–PPF, (<b>i</b>) PPT–PPF, (<b>j</b>) PCHDMF–PPF.</p> Full article ">Figure 7 Cont.
<p>SEM photographs showing the melt-quenched samples of 50-50 blends: (<b>a</b>) PC–PEF, (<b>b</b>) PEN–PEF, (<b>c</b>) PET–PEF, (<b>d</b>) PCHDMF–PEF, (<b>e</b>) PLA–PEF, (<b>f)</b> PPF–PEF, (<b>g</b>) PBF–PEF, (<b>h</b>) PBF–PPF, (<b>i</b>) PPT–PPF, (<b>j</b>) PCHDMF–PPF.</p> Full article ">Figure 8
<p>(<b>a</b>) DSC heating thermograms, (<b>b</b>) details of DSC thermograms in the T<sub>g</sub> region and (<b>c</b>) derivative heat flow for melt-quenched PCHDMF–PPF blend samples.</p> Full article ">Figure 9
<p>(<b>a</b>) DSC heating thermograms, (<b>b</b>) details of DSC thermograms in the T<sub>g</sub> region and (<b>c</b>) derivative heat flow for melt-quenched PEN–PEF blend samples.</p> Full article ">Figure 9 Cont.
<p>(<b>a</b>) DSC heating thermograms, (<b>b</b>) details of DSC thermograms in the T<sub>g</sub> region and (<b>c</b>) derivative heat flow for melt-quenched PEN–PEF blend samples.</p> Full article ">Figure 10
<p>(<b>a</b>) DSC heating thermograms, and (<b>b</b>) derivative heat flow for melt-quenched PC–PPF blend samples.</p> Full article ">Figure 11
<p>(<b>a</b>) DSC heating thermograms, (<b>b</b>) details of DSC thermograms in the T<sub>g</sub> region and (<b>c</b>) derivative heat flow for melt-quenched PLA–PPF blend samples.</p> Full article ">Figure 12
<p>(<b>a</b>) DSC heating thermograms, (<b>b</b>) details of DSC thermograms in the T<sub>g</sub> region, for melt- quenched PPF blend samples with various polymers and 50-50 composition.</p> Full article ">Figure 13
<p>(<b>a</b>) DSC heating thermograms, (<b>b</b>) details of DSC thermograms in the T<sub>g</sub> region for melt- quenched PBF blend samples with various polymers and 50-50 composition.</p> Full article ">Scheme 1
<p>Pathway for synthesis of poly(alkylene 2,5-furandicarboxylate)s.</p> Full article ">
17 pages, 12479 KiB  
Article
Correlation between Drop Impact Energy and Residual Compressive Strength According to the Lamination of CFRP with EVA Sheets
by Sun-Ho Go, Min-Sang Lee, Chang-Gi Hong, Lee-Ku Kwac and Hong-Gun Kim
Polymers 2020, 12(1), 224; https://doi.org/10.3390/polym12010224 - 16 Jan 2020
Cited by 10 | Viewed by 3306
Abstract
Carbon-fiber-reinforced plastic is an important building material; however, its application is limited because of its brittleness, leading to vulnerability under shock. Thus, the strength performance of carbon-fiber-reinforced plastics needs to be improved. Here, the drop impact test was conducted to analyze the impact [...] Read more.
Carbon-fiber-reinforced plastic is an important building material; however, its application is limited because of its brittleness, leading to vulnerability under shock. Thus, the strength performance of carbon-fiber-reinforced plastics needs to be improved. Here, the drop impact test was conducted to analyze the impact energy and fracture characteristics of carbon-fiber-reinforced plastics and ethylene vinyl acetate sheets. The compression after impact test was performed to assess the residual compressive strength. The thermal energy generated was measured as change in temperature at the time of fracture to investigate the relationship between thermal and mechanical properties. The impact absorption efficiency of 100% was achieved when the carbon-fiber-reinforced plastics specimen was laminated with four or more sheets of ethylene vinyl acetate. The thermal energy generated during impact, the impact load, and the compression after impact test strength was reduced with the increasing number of laminated ethylene vinyl acetate layers. Our results showed that, by carefully selecting the optimal conditions of fabricating the carbon-fiber-reinforced plastic/ethylene vinyl acetate composites, carbon composite materials can be used for impact mitigation. Full article
(This article belongs to the Special Issue Multiphase Structure of Polymeric Materials and Physical Properties)
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<p>The set-up for specimen manufacturing: (<b>a</b>) autoclave machine, and (<b>b</b>) curing cycle of carbon-fiber-reinforced plastic (CFRP) stacking specimen.</p> Full article ">Figure 2
<p>Set-up of experiments: (<b>a</b>) drop weight testing, and (<b>b</b>) compression after impact (CAI) testing.</p> Full article ">Figure 3
<p>Impact test results of Type 1: (<b>a</b>) changes in load and energy with time, (<b>b</b>) impact load and displacement curve, (<b>c</b>) changes in temperature with time, (<b>d</b>) impact test of specimen Type 1, and (<b>e</b>) infrared (IR) image of the impact test (Type 1).</p> Full article ">Figure 4
<p>Impact test results of Type 2: (<b>a</b>) changes in load and energy with time, (<b>b</b>) impact load and displacement curve, (<b>c</b>) changes in temperature with time, (<b>d</b>) impact test of specimen Type 2, and (<b>e</b>) IR image of impact test (Type 2).</p> Full article ">Figure 5
<p>Impact test results of Type 3: (<b>a</b>) changes in load and energy with time, (<b>b</b>) impact load and displacement curve, (<b>c</b>) changes in temperature with time, (<b>d</b>) impact test of specimen Type 3, and (<b>e</b>) IR image of impact test (Type 3).</p> Full article ">Figure 6
<p>Impact test results of Type 4: (<b>a</b>) changes in load and energy with time, (<b>b</b>) impact load and displacement curve, (<b>c</b>) changes in temperature with time, (<b>d</b>) impact test of specimen Type 4, and (<b>e</b>) IR image of impact test (Type 4).</p> Full article ">Figure 7
<p>Impact test results of Type 5: (<b>a</b>) changes in load and energy with time, (<b>b</b>) impact load and displacement curve, (<b>c</b>) changes in temperature with time, (<b>d</b>) impact test of specimen Type 5, and (<b>e</b>) IR image of impact test (Type 5).</p> Full article ">Figure 8
<p>Comparative results for impact test: (<b>a</b>) energy absorption efficiency of each type and (<b>b</b>) impact load and temperature of each type.</p> Full article ">Figure 9
<p>Load and displacement curve of the CAI test, (<b>a</b>) Type 1 (24 CFRP), (<b>b</b>) Type1-0 (24 CFRP, without impact test), (<b>c</b>) Type 2 (20CFRP:2EVA), (<b>d</b>) Type 3 (16CFRP:4EVA), (<b>e</b>) Type 4 (8CFRP:8EVA, inside), (<b>f</b>) Type 5 (8CFRP:8EVA, outside).</p> Full article ">Figure 10
<p>Thermal images of CAI tested specimens, (<b>a</b>) Type 1 (24 CFRP), (<b>b</b>) Type 2 (20CFRP:2EVA), (<b>c</b>) Type 3 (16CFRP:4EVA), (<b>d</b>) Type 4 (8CFRP:8EVA, inside), (<b>e</b>) Type 5 (8CFRP:8EVA, outside).</p> Full article ">Figure 11
<p>Comparison of the test results: (<b>a</b>) compression residual strength and impact load of each type, and (<b>b</b>) compression residual strength and temperature of each type.</p> Full article ">Figure 12
<p>SEM images of each type before and after testing, (<b>a</b>) Type 1 (24 CFRP), (<b>b</b>) Type 2 (20CFRP:2EVA), (<b>c</b>) Type 3 (16CFRP:4EVA), (<b>d</b>) Type 4 (8CFRP:8EVA, inside), (<b>e</b>) Type 5 (8CFRP:8EVA, outside).</p> Full article ">
14 pages, 3545 KiB  
Article
Fluorinated Montmorillonite and 3YSZ as the Inorganic Fillers in Fluoride-Releasing and Rechargeable Dental Composition Resin
by Keng-Yuan Li, Cheng-Chia Tsai, Tzu-Chieh Lin, Yin-Lin Wang, Feng-Huei Lin and Chun-Pin Lin
Polymers 2020, 12(1), 223; https://doi.org/10.3390/polym12010223 - 16 Jan 2020
Cited by 10 | Viewed by 4421
Abstract
Dental caries (tooth decay) is the most frequent oral disease in humans. Filling cavities with a dental restorative material is the most common treatment, and glass ionomer cements are the main fluoride ion release restorative materials. The goal of this study was to [...] Read more.
Dental caries (tooth decay) is the most frequent oral disease in humans. Filling cavities with a dental restorative material is the most common treatment, and glass ionomer cements are the main fluoride ion release restorative materials. The goal of this study was to develop a restorative compound with superior fluoride ion release and recharge abilities. Previously developed fluorinated bentolite and hydrophobized 3YSZ were used as two different inorganic fillers mixed in a bisphenol A-glycidyl methacrylate (Bis-GMA) matrix. XRD, FTIR, and TGA were used to determine the hydrophobic modification of these two inorganic fillers. In mechanical tests, including diameter tensile strength, flexural strength, and wear resistance, the developed composite resin was significantly superior to the commercial control. A WST-1 assay was used to confirm that the material displayed good biocompatibility. Furthermore, the simulation of the oral environment confirmed that the composite resin had good fluoride ion release and reloading abilities. Thus, the composite resin developed in this study may reduce secondary caries and provide a new choice for future clinical treatments. Full article
(This article belongs to the Special Issue Polymeric Materials for Dental Applications)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>XRD analysis of montmorillonite (MMT) and the NaF-intercalated fluorinated montmorillonite (FMMT/AAm-NaF): (<b>a</b>) XRD patterns of MMT and the FMMT/AAm-NaF from 2° to 8°. The (001) plane angle is marked with a star; (<b>b</b>) XRD patterns of 3YSZ and the 3YSZ/MPTMS from 25° to 65° compared with the underlined references of the Joint Committee on Powder Diffraction Standards (JCPDS) card No. 50-1089 for ZrO<sub>2</sub> tetragonal and No. 37-1484 for ZrO<sub>2</sub> monoclinic.</p> Full article ">Figure 2
<p>FTIR spectra analysis of the prepared composites: (<b>a</b>) FTIR spectra (500–2000 cm<sup>−1</sup>) of MMT, AAm, and the FMMT/AAm-NaF; (<b>b</b>) FTIR spectra (500–4000 cm<sup>−1</sup>) of 3YSZ, MPTMS, and the 3YSZ/MPTMS.</p> Full article ">Figure 3
<p>Thermogravimetric curve analysis: (<b>a</b>) TGA patterns of MMT, FMMT, and the FMMT/AAm-NaF between 100 and 700 °C; (<b>b</b>) TGA patterns of 3YSZ and the 3YSZ/MPTMS between 100 and 700 °C.</p> Full article ">Figure 4
<p>Particle size and cumulative size distribution analysis: (<b>a</b>) particle size distribution (red columns) and cumulative size distribution (blue line) of the FMMT/AAm-NaF; (<b>b</b>) particle size distribution (red columns) and cumulative size distribution (blue line) of the 3YSZ/MPTMS.</p> Full article ">Figure 5
<p>Curing depths of the developed fluoride-releasing composite resin (FCR) and stated in the ISO 4049 standard. *** denotes <span class="html-italic">p</span> &lt; 0.001.</p> Full article ">Figure 6
<p>Mechanical properties of the FCR and the commercial product Fuji IXGP: (<b>a</b>) microhardness; (<b>b</b>) diametral tensile strength; (<b>c</b>) flexural strength; (<b>d</b>) wear resistance. *** denotes <span class="html-italic">p</span> &lt; 0.001.</p> Full article ">Figure 7
<p>Fluoride release analysis of the developed FCR and commercial Fuji IXGP: (<b>a</b>) fluoride release per cm<sup>2</sup> of the FCR and Fuji IXGP each day for two weeks. No significant difference was observed on day 4; (<b>b</b>) cumulative fluoride release of the FCR and Fuji IXGP each day for two weeks. Significant differences existed at all time points.</p> Full article ">Figure 8
<p>Analysis of fluoride release after recharge: (<b>a</b>) postrecharge fluoride release per cm<sup>2</sup> of Fuji IXGP and the FCR each day for seven days. Significant differences were observed between the materials in the first three days; (<b>b</b>) cumulative fluoride release from Fuji IXGP and the FCR after recharge every day for seven days. Significant differences existed at all times.</p> Full article ">Figure 9
<p>WST-1 assay of the control group, positive control group, and FCR extraction solution-treated 3T3 cells at days 1, 2, and 3. Only the positive control group was statistically significantly different from the other two groups (*** denotes <span class="html-italic">p</span> &lt; 0.001).</p> Full article ">
13 pages, 2785 KiB  
Article
Poly-(3-ethyl-3-hydroxymethyl)oxetanes—Synthesis and Adhesive Interactions with Polar Substrates
by Paweł Parzuchowski and Mariusz Ł. Mamiński
Polymers 2020, 12(1), 222; https://doi.org/10.3390/polym12010222 - 16 Jan 2020
Cited by 8 | Viewed by 3426
Abstract
Hyperbranched polyoxetanes are a relatively new class of polymers. These are branched polyethers that are synthesized from oxetanes—four-member cyclic ethers bearing hydroxymethyl groups—via ring-opening polymerization. Four series of polyoxetanes were synthesized from 3-ethyl-3-(hydroxymethyl)oxetane and 1,1,1-tris(hydroxymethyl)propane as a core molecule. Reagents ratios ranged from [...] Read more.
Hyperbranched polyoxetanes are a relatively new class of polymers. These are branched polyethers that are synthesized from oxetanes—four-member cyclic ethers bearing hydroxymethyl groups—via ring-opening polymerization. Four series of polyoxetanes were synthesized from 3-ethyl-3-(hydroxymethyl)oxetane and 1,1,1-tris(hydroxymethyl)propane as a core molecule. Reagents ratios ranged from 1:5 to 1:50, theoretical molar mass ranged from 714 g/mol to 5942 g/mol, and dispersities ranged from 1.77 to 3.75. The morphology of the macromolecules was investigated by a matrix-assisted laser desorption/ionization time of flight technique. The polyoxetanes’ adhesive interactions with polar materials were analyzed and provided results as follows: the work of adhesion was 101–105 mJ/m2, the bond-line tensile shear strengths were 0.39–1.32 MPa, and there was a brittle fracture mode within the polymer. The findings confirmed a good adhesion to polar substrates, but further research on polyoxetane modifications toward a reduction of brittleness is necessary. Full article
(This article belongs to the Section Polymer Chemistry)
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Figure 1

Figure 1
<p>Cationic polymerization of 3-ethyl-3-hydroxymethyloxetane.</p> Full article ">Figure 2
<p><sup>1</sup>H NMR (400 MHz, DMSO-d<sub>6</sub>) spectrum of poly(3-ethyl-3-hydroxymethyloxetane).</p> Full article ">Figure 3
<p><sup>13</sup>C NMR (400 MHz, DMSO-d<sub>6</sub>) spectrum of poly(3-ethyl-3-hydroxymethyloxetane) of degree of branching equal to 0.36.</p> Full article ">Figure 4
<p><sup>1</sup>H NMR (400 MHz, DMSO-d<sub>6</sub>) spectra of the studied polyoxetanes.</p> Full article ">Figure 5
<p>FTIR spectra of poly(3-ethyl-3-(hydroxymethyl)oxetanes).</p> Full article ">Figure 6
<p>MALDI-TOF (DCTB, Na+) spectrum of POX with 1,1,1-tris(hydroxymethyl)propane (TMP) core; a-a distance <span class="html-italic">Δm/z</span> = 116.</p> Full article ">Figure 7
<p>Shear strengths of the POX bond-lines.</p> Full article ">Figure 8
<p>Cohesive fracture in POXs layers of different TMP/EHO (3-ethyl-3-(hydroxymethyl)oxetane) ratios.</p> Full article ">Figure 9
<p>The effect of the reagent ratio in the POX molecule on load bearing ability.</p> Full article ">
14 pages, 3695 KiB  
Article
Thermal Analysis and Crystal Structure of Poly(Acrylonitrile-Co-Itaconic Acid) Copolymers Synthesized in Water
by Hailong Zhang, Ling Quan, Aijun Gao, Yuping Tong, Fengjun Shi and Lianghua Xu
Polymers 2020, 12(1), 221; https://doi.org/10.3390/polym12010221 - 16 Jan 2020
Cited by 28 | Viewed by 5485
Abstract
The composition and structure of polyacrylonitrile (PAN) precursors play an important role during thermal stabilization, which influences the properties of the resulting carbon fibers. In this paper, PAN homopolymer and PAN-itaconic (IA) copolymers with different IA contents were synthesized by aqueous phase precipitation [...] Read more.
The composition and structure of polyacrylonitrile (PAN) precursors play an important role during thermal stabilization, which influences the properties of the resulting carbon fibers. In this paper, PAN homopolymer and PAN-itaconic (IA) copolymers with different IA contents were synthesized by aqueous phase precipitation polymerization. The effects of IA content on the structure and thermal properties were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The morphology of PAN polymers showed that the average size of the PAN particles increased with the increase of IA content in the feed. The content of the IA comonomer on the copolymers was quantitatively characterized by the relative absorbance intensity (A1735/A2243) in FTIR spectrum. With the increase of IA content in the feed, PAN-IA copolymers exhibited lower degree of crystallinity and crystal size than the control PAN homopolymer. The results from DSC curves indicated that PAN-IA1.0 copolymers had lower initial exothermic temperature (192.4 °C) and velocity of evolving heat (6.33 J g−1 °C−1) in comparison with PAN homopolymer (Ti = 238.1 °C and ΔH/ΔT = 34.6 J g−1 °C−1) in an air atmosphere. TGA results suggested that PAN-IA1.0 copolymers had higher thermal stability than PAN homopolymer, which can form a ladder structure easier during thermal processing. Therefore, PAN-IA1.0 copolymers would be a suitable candidate for preparing high performance PAN based carbon fibers. Full article
(This article belongs to the Special Issue Thermal Properties and Applications of Polymers II)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Synthetic route of (<b>a</b>) Polyacrylonitrile (PAN) homopolymer and (<b>b</b>) PAN-itaconic acid (IA) copolymers.</p> Full article ">Figure 2
<p>Scanning Electron Microscopy (SEM) micrographs of (<b>a</b>,<b>b</b>) PAN homopolymer, (<b>c</b>,<b>d</b>) PAN-IA0.5 copolymers, and (<b>e</b>,<b>f</b>) PAN-IA1.0 copolymers.</p> Full article ">Figure 3
<p>Fourier Transform Infrared Spectroscopy (FTIR) spectra of (<b>a</b>) PAN homopolymer, (<b>b</b>) PAN-IA0.5 copolymers, and (<b>c</b>) PAN-IA1.0 copolymers (<b>left</b> figure). Amplification section of –COOH groups in FTIR (<b>right</b> figure).</p> Full article ">Figure 4
<p>X-ray Diffraction (XRD) patterns of (<b>a</b>) PAN homopolymer, (<b>b</b>) PAN-IA0.5 copolymers, and (<b>c</b>) PAN-IA1.0 copolymers.</p> Full article ">Figure 5
<p>Differential Scanning Calorimetry (DSC) curves of (<b>a</b>) PAN homopolymer, (<b>b</b>) PAN-IA0.5 copolymers, and (<b>c</b>) PAN-IA1.0 copolymers in a nitrogen atmosphere.</p> Full article ">Figure 6
<p>Cyclization reaction: (<b>a</b>) the free radical mechanism and (<b>b</b>) the ionic mechanism.</p> Full article ">Figure 7
<p>DSC curves of (<b>a</b>) PAN homopolymer, (<b>b</b>) PAN-IA0.5 copolymers, and (<b>c</b>) PAN-IA1.0 copolymers in an air atmosphere.</p> Full article ">Figure 8
<p>Thermogravimetric Analysis (TGA) curves of (<b>a</b>) PAN homopolymer, (<b>b</b>) PAN-IA0.5 copolymers, and (<b>c</b>) PAN-IA1.0 copolymers in a nitrogen atmosphere.</p> Full article ">Figure 9
<p>Derivative Thermogravimetric (DTG) curves of (<b>a</b>) PAN homopolymer, (<b>b</b>) PAN-IA0.5 copolymers and (<b>c</b>) PAN-IA1.0 copolymers.</p> Full article ">
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