Polymers

15 pages, 3287 KiB

Open AccessArticle

Transient Thermal Tensile Behaviour of Novel Pitch-Based Ultra-High Modulus CFRP Tendons

by Giovanni Pietro Terrasi^1,2,*, Emma R. E. McIntyre², Luke A. Bisby², Tobias D. Lämmlein¹

and Pietro Lura^3,4

¹ Mechanical Systems Engineering Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland

² BRE Centre for Fire Safety Engineering, Institute for Infrastructure & Environment, School of Engineering, University of Edinburgh, The King’s Buildings Edinburgh, EH93JL Scotland, UK

³ Concrete and Construction Chemistry Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland

⁴ Institute for Building Materials (IfB), ETH Zurich, 8092 Zurich, Switzerland

Polymers 2016, 8(12), 446; https://doi.org/10.3390/polym8120446 - 21 Dec 2016

Cited by 8 | Viewed by 6756

Abstract

A novel ultra-high modulus carbon fibre reinforced polymer (CFRP) prestressing tendon made from coal tar pitch-based carbon fibres was characterized in terms of high temperature tensile strength (up to 570 °C) with a series of transient thermal and steady state temperature tensile tests. [...] Read more.

A novel ultra-high modulus carbon fibre reinforced polymer (CFRP) prestressing tendon made from coal tar pitch-based carbon fibres was characterized in terms of high temperature tensile strength (up to 570 °C) with a series of transient thermal and steady state temperature tensile tests. Digital image correlation was used to capture the high temperature strain development during thermal and mechanical loading. Complementary thermogravimetric (TGA) and dynamic mechanical thermal (DMTA) experiments were performed on the tendons to elucidate their high temperature thermal and mechanical behaviour. The novel CFRP tendons investigated in the present study showed an ambient temperature design tensile strength of 1400 MPa. Their failure temperature at a sustained prestress level of 50% of the design tensile strength was 409 °C, which is higher than the failure temperature of most fibre reinforced polymer rebars used in civil engineering applications at similar utilisation levels. This high-temperature tensile strength shows that there is potential to use the novel high modulus CFRP tendons in CFRP pretensioned concrete elements for building applications that fulfill the fire resistance criteria typically applied within the construction industry. Full article

(This article belongs to the Collection Fiber-Reinforced Polymer Composites in Structural Engineering)

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12 pages, 3790 KiB

Open AccessArticle

Design of Graphene- and Polyaniline-Containing Functional Polymer Hydrogel as a New Adsorbent for Removal of Chromium (VI) Ions

by Jae-Seo Chin^1,†, Anantha-Iyengar Gopalan^2,3,†

, Nallal Muthuchamy¹

and Kwang-Pill Lee^1,2,3,*

¹ Department of Chemistry Education, Kyungpook National University, Daegu 41566, Korea

² Department of Nanoscience and Nanotechnology, Kyungpook National University, Daegu 41566, Korea

³ Research Institute of Advanced Energy Technology, Kyungpook National University, Daegu 41566, Korea

^† These authors contributed equally to this work.

Polymers 2016, 8(12), 445; https://doi.org/10.3390/polym8120445 - 21 Dec 2016

Cited by 12 | Viewed by 6755

Abstract

Hydrogels find applications in various fields, and the ever-growing spectrum of available monomers, crosslinking, and nanotechnologies widen the application of polymer hydrogels. Herein, we describe the preparation of a new graphene (G)- and polyaniline (PANI)-containing functional polymer gel (G/PANI/FG) through a facile crosslinking [...] Read more.

Hydrogels find applications in various fields, and the ever-growing spectrum of available monomers, crosslinking, and nanotechnologies widen the application of polymer hydrogels. Herein, we describe the preparation of a new graphene (G)- and polyaniline (PANI)-containing functional polymer gel (G/PANI/FG) through a facile crosslinking copolymerization approach. Several characterization techniques such as field-emission scanning electron microscopy, Fourier-transform infrared, and X-ray photoelectron spectroscopy were employed to understand the physicochemical characteristics of the G/PANI/FG. The new G/PANI/FG was used as an adsorbent for chromium (VI) and exhibited the highest Cr (VI) removal efficiency (~97%). The inclusion of G and PANI in the gel results in high surface area, 3D porous structure, and Cr (VI)-chelating amine sites, which enhanced the Cr (VI) removal efficiency and thermal stability of the gel adsorbent. The results of our study revealed that G/PANI/FG is suited for the removal of Cr (VI) from aqueous solution. Full article

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17 pages, 4199 KiB

Open AccessArticle

Investigations on Green Blends Comprising Biodegradable Polymer and Ionic Liquid

by Li-Ting Lee^* and Chun-Ting Yang

Department of Materials Science and Engineering, Feng Chia University, Taichung 40724, Taiwan

Polymers 2016, 8(12), 444; https://doi.org/10.3390/polym8120444 - 21 Dec 2016

Cited by 9 | Viewed by 5954

Abstract

The green blends of an ionic liquid, 1-ethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide {[EPrI][TFSI]}, and a biodegradable polymer, poly(3-hydroxybutyrate) (PHB), were investigated in this study. The influence of an ionic liquid on the crystallization behaviors of a biodegradable polymer was explored. In the blends, the presence of [...] Read more.

The green blends of an ionic liquid, 1-ethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide {[EPrI][TFSI]}, and a biodegradable polymer, poly(3-hydroxybutyrate) (PHB), were investigated in this study. The influence of an ionic liquid on the crystallization behaviors of a biodegradable polymer was explored. In the blends, the presence of [EPrI][TFSI] decreased the T_g and T_m of PHB. Incorporating [EPrI][TFSI] in the blends reduced the degree of crystallinity of PHB, inferring that the [EPrI][TFSI] weakened the crystallization of PHB. It further showed retarded isothermal and non-isothermal crystallization for PHB with the presence of [EPrI][TFSI]. The smaller K and 1/t_0.5 estimated by the Avrami equation for the blends indicated that [EPrI][TFSI] weakened the isothermal crystallization of PHB with exhibiting the slower crystallization rate. The present study also discussed non-isothermal crystallization of the blends. We found that the Mo model, which is generally used to discuss the non-isothermal crystallization, adequately described the non-isothermal behaviors of the [EPrI][TFSI]/PHB blends. By increasing the [EPrI][TFSI] content, the rate-related parameter F(T) systematically increased, inferring a decreased crystallization rate of PHB with the addition of [EPrI][TFSI] in the blends. The FTIR results suggested an ion–dipole interaction between [EPrI][TFSI] and PHB. This proposes the occurrence of possible complexation between [EPrI][TFSI] and PHB. Full article

(This article belongs to the Special Issue Polymer Blends 2017)

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13 pages, 20983 KiB

Open AccessArticle

A Highly Hydrophilic and Biodegradable Novel Poly(amide-imide) for Biomedical Applications

by Qiying Zou, Qian Zhou, Langlang Liu and Honglian Dai^*

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China

Polymers 2016, 8(12), 441; https://doi.org/10.3390/polym8120441 - 19 Dec 2016

Cited by 9 | Viewed by 7333

Abstract

A novel biodegradable poly(amide-imide) (PAI) with good hydrophilicity was synthesized by incorporation of l-glycine into the polymer chain. For comparison purposes, a pure PAI containing no l-glycine was also synthesized with a three-step method. In this study, we evaluated the novel [...] Read more.

A novel biodegradable poly(amide-imide) (PAI) with good hydrophilicity was synthesized by incorporation of l-glycine into the polymer chain. For comparison purposes, a pure PAI containing no l-glycine was also synthesized with a three-step method. In this study, we evaluated the novel PAI’s thermal stability, hydrophilicity, solubility, biodegradability and ability to support bone marrow mesenchymal stem cell (BMSC) adhesion and growth by comparing with the pure PAI. The hydrophilic tests demonstrated that the novel PAI has possible hydrophilicity at a 38° water contact angle on the molecule surface and is about two times more hydrophilic than the pure PAI. Due to an extra unit of l-glycine in the novel PAI, the average degradation rate was about 2.4 times greater than that of the pure PAI. The preliminary biocompatibility studies revealed that all the PAIs are cell compatible, but the pure PAI exhibited much lower cell adhesion than the l-glycine-incorporated novel PAI. The hydrophilic surface of the novel PAI was more suitable for cell adhesion, suggesting that the surface hydrophilicity plays an important role in enhancing cell adhesion and growth. Full article

(This article belongs to the Special Issue Biodegradable Polymers)

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15 pages, 6523 KiB

Open AccessArticle

Synthesis of Polythiophene–Fullerene Hybrid Additives as Potential Compatibilizers of BHJ Active Layers

by Sofia Kakogianni¹, Aikaterini K. Andreopoulou^1,2,*

and Joannis K. Kallitsis^1,2

¹ Department of Chemistry, University of Patras, University Campus, GR26504 Patras, Greece

² Foundation for Research and Technology Hellas/Institute of Chemical Engineering Sciences (FORTH/ICE-HT), GR26504 Patras, Greece

Polymers 2016, 8(12), 440; https://doi.org/10.3390/polym8120440 - 18 Dec 2016

Cited by 13 | Viewed by 7243

Abstract

Perfluorophenyl functionalities have been introduced as side chain substituents onto regioregular poly(3-hexyl thiophene) (rr-P3HT), under various percentages. These functional groups were then converted to azides which were used to create polymeric hybrid materials with fullerene species, either C₆₀ or C [...] Read more.

Perfluorophenyl functionalities have been introduced as side chain substituents onto regioregular poly(3-hexyl thiophene) (rr-P3HT), under various percentages. These functional groups were then converted to azides which were used to create polymeric hybrid materials with fullerene species, either C₆₀ or C₇₀. The P3HT–fullerene hybrids thus formed were thereafter evaluated as potential compatibilizers of BHJ active layers comprising P3HT and fullerene based acceptors. Therefore, a systematic investigation of the optical and morphological properties of the purified polymer–fullerene hybrid materials was performed, via different complementary techniques. Additionally, P3HT:PC₇₀BM blends containing various percentages of the herein synthesized hybrid material comprising rr-P3HT and C₇₀ were investigated via Transmission Electron Microscopy (TEM) in an effort to understand the effect of the hybrids as additives on the morphology and nanophase separation of this typically used active layer blend for OPVs. Full article

(This article belongs to the Special Issue Hybrid Polymeric Materials)

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34 pages, 5619 KiB

Open AccessReview

Applications of Solid-State NMR Spectroscopy for the Study of Lipid Membranes with Polyphilic Guest (Macro)Molecules

by Ruth Bärenwald, Anja Achilles, Frank Lange, Tiago Mendes Ferreira and Kay Saalwächter^*

Institut für Physik—NMR, Martin-Luther-Universität Halle-Wittenberg, D-06120 Halle, Germany

Polymers 2016, 8(12), 439; https://doi.org/10.3390/polym8120439 - 16 Dec 2016

Cited by 15 | Viewed by 10224

Abstract

The incorporation of polymers or smaller complex molecules into lipid membranes allows for property modifications or the introduction of new functional elements. The corresponding molecular-scale details, such as changes in dynamics or features of potential supramolecular structures, can be studied by a variety [...] Read more.

The incorporation of polymers or smaller complex molecules into lipid membranes allows for property modifications or the introduction of new functional elements. The corresponding molecular-scale details, such as changes in dynamics or features of potential supramolecular structures, can be studied by a variety of solid-state NMR techniques. Here, we review various approaches to characterizing the structure and dynamics of the guest molecules as well as the lipid phase structure and dynamics by different high-resolution magic-angle spinning proton and ¹³C NMR experiments as well as static ³¹P NMR experiments. Special emphasis is placed upon the incorporation of novel synthetic polyphilic molecules such as shape-persistent T- and X-shaped molecules as well as di- and tri-block copolymers. Most of the systems studied feature dynamic heterogeneities, for instance those arising from the coexistence of different phases; possibilities for a quantitative assessment are of particular concern. Full article

(This article belongs to the Special Issue From Amphiphilic to Polyphilic Polymers)

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11 pages, 2548 KiB

Open AccessArticle

Electroosmotic Flow in Mixed Polymer Brush-Grafted Nanochannels

by Qianqian Cao^1,* and Hao You^2,*

¹ College of Mechanical and Electrical Engineering, Jiaxing University, Jiaxing 314001, China

² Center for Simulational Physics, Department of Physics and Astronomy, University of Georgia, Athens, GA 30602, USA

Polymers 2016, 8(12), 438; https://doi.org/10.3390/polym8120438 - 16 Dec 2016

Cited by 19 | Viewed by 6392

Abstract

Mixed polymer brush-grafted nanochannels—where two distinct species of polymers are alternately grafted on the inner surface of nanochannels—are an interesting class of nanostructured hybrid materials. By using a coarse-grained molecular dynamics simulation method, we are able to simulate the electrokinetic transport dynamics of [...] Read more.

Mixed polymer brush-grafted nanochannels—where two distinct species of polymers are alternately grafted on the inner surface of nanochannels—are an interesting class of nanostructured hybrid materials. By using a coarse-grained molecular dynamics simulation method, we are able to simulate the electrokinetic transport dynamics of the fluid in such nanochannels as well as the conformational behaviors of the mixed polymer brush. We find that (1) the brush adopts vertically-layered and longitudinally-separated structures due to the coupling of electroosmotic flow (EOF) and applied electric field; (2) the solvent quality affects the brush conformations and the transport properties of the EOF; (3) the EOF flux non-monotonically depends on the grafting density, although the EOF velocity in the central region of the channel monotonically depends on the grafting density. Full article

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10 pages, 1347 KiB

Open AccessArticle

Study on Hydrogen Sensitivity of Ziegler–Natta Catalysts with Novel Cycloalkoxy Silane Compounds as External Electron Donor

by Hongming Li^1,2, Jing Wang¹, Lei He¹, Feng Nan¹, Fan Wang¹, Wantai Yang¹, Mingge Zhang², Tianxu Sun², Qigu Huang^1,* and Jianjun Yi^2,*

¹ State Key Laboratory of Chemical Resource Engineering, Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, the College of Material Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China

² Petrochemical Research Institute, PetroChina, Beijing 102206, China

Polymers 2016, 8(12), 433; https://doi.org/10.3390/polym8120433 - 16 Dec 2016

Cited by 10 | Viewed by 9307

Abstract

Two novel cycloalkoxy silane compounds (ED1 and ED2) were synthesized and used as the external electron donors (EEDs) in Ziegler–Natta catalysts with diethyl 2,3-diisopropylsuccinate as internal electron donor. The results indicated that the Ziegler–Natta catalysts using ED1 and ED2 as EEDs had high [...] Read more.

Two novel cycloalkoxy silane compounds (ED1 and ED2) were synthesized and used as the external electron donors (EEDs) in Ziegler–Natta catalysts with diethyl 2,3-diisopropylsuccinate as internal electron donor. The results indicated that the Ziegler–Natta catalysts using ED1 and ED2 as EEDs had high catalytic activities and good stereoselectivities. The melt flow rate (MFR) and gel permeation chromatography (GPC) results revealed that the obtained polypropylene has higher MFR and lower average molecular weights than the commercial EED cyclohexyl methyl dimethoxysilane. The differential scanning calorimetry (DSC) results indicated that new isospecific active centers formed after the introduction of new external donors. The work implied that the novel EEDs could improve the hydrogen sensitivities of the catalyst system and obtain polymers with high melt flow rate. Full article

(This article belongs to the Collection Silicon-Containing Polymeric Materials)

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13 pages, 3426 KiB

Open AccessArticle

Creep and Recovery Behaviour of Polyolefin-Rubber Nanocomposites Developed for Additive Manufacturing

by Fugen Daver^1,*

, Mladenko Kajtaz¹

, Milan Brandt¹ and Robert A. Shanks²

¹ School of Engineering, RMIT University, P.O. Box 71, Bundoora, Victoria 3083, Australia

² School of Science, RMIT University, GPO Box 2476, Melbourne, Victoria 3001, Australia

Polymers 2016, 8(12), 437; https://doi.org/10.3390/polym8120437 - 15 Dec 2016

Cited by 41 | Viewed by 13214

Abstract

Nanocomposite application in automotive engineering materials is subject to continual stress fields together with recovery periods, under extremes of temperature variations. The aim is to prepare and characterize polyolefin-rubber nanocomposites developed for additive manufacturing in terms of their time-dependent deformation behaviour as revealed [...] Read more.

Nanocomposite application in automotive engineering materials is subject to continual stress fields together with recovery periods, under extremes of temperature variations. The aim is to prepare and characterize polyolefin-rubber nanocomposites developed for additive manufacturing in terms of their time-dependent deformation behaviour as revealed in creep-recovery experiments. The composites consisted of linear low density polyethylene and functionalized rubber particles. Maleic anhydride compatibilizer grafted to polyethylene was used to enhance adhesion between the polyethylene and rubber; and multi-walled carbon nanotubes were introduced to impart electrical conductivity. Various compositions of nanocomposites were tested under constant stress in creep and recovery. A four-element mechanistic Burger model was employed to model the creep phase of the composites, while a Weibull distribution function was employed to model the recovery phase of the composites. Finite element analysis using Abaqus enabled numerical modelling of the creep phase of the composites. Both analytical and numerical solutions were found to be consistent with the experimental results. Creep and recovery were dependent on: (i) composite composition; (ii) compatibilizers content; (iii) carbon nanotubes that formed a percolation network. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2016)

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15 pages, 2723 KiB

Open AccessArticle

Healing of Early Stage Fatigue Damage in Ionomer/Fe₃O₄ Nanoparticle Composites

by Wouter Post, Ranjita K. Bose, Santiago J. García^*

and Sybrand Van der Zwaag

Novel Aerospace Materials, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands

Polymers 2016, 8(12), 436; https://doi.org/10.3390/polym8120436 - 15 Dec 2016

Cited by 20 | Viewed by 7641

Abstract

This work reports on the healing of early stage fatigue damage in ionomer/nano-particulate composites. A series of poly(ethylene-co-methacrylic acid) zinc ionomer/Fe₃O₄ nanoparticle composites with varying amounts of ionic clusters were developed and subjected to different levels of fatigue [...] Read more.

This work reports on the healing of early stage fatigue damage in ionomer/nano-particulate composites. A series of poly(ethylene-co-methacrylic acid) zinc ionomer/Fe₃O₄ nanoparticle composites with varying amounts of ionic clusters were developed and subjected to different levels of fatigue loading. The initiated damage was healed upon localized inductive heating of the embedded nanoparticles by exposure of the particulate composite to an alternating magnetic field. It is here demonstrated that healing of this early stage damage in ionomer particulate composites occurs in two different steps. First, the deformation is restored by the free-shrinkage of the polymer at temperatures below the melt temperature. At these temperatures, the polymer network is recovered thereby resetting the fatigue induced strain hardening. Then, at temperatures above the melting point of the polymer phase, fatigue-induced microcracks are sealed, hereby preventing crack propagation upon further loading. It is shown that the thermally induced free-shrinkage of these polymers does not depend on the presence of ionic clusters, but that the ability to heal cracks by localized melting while maintaining sufficient mechanical integrity is reserved for ionomers that contain a sufficient amount of ionic clusters guaranteeing an acceptable level of mechanical stability during healing. Full article

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14 pages, 3984 KiB

Open AccessArticle

Influence of a Crosslinker Containing an Azo Group on the Actuation Properties of a Photoactuating LCE System

by Lukas B. Braun, Torsten G. Linder, Tristan Hessberger and Rudolf Zentel^*

Institute of Organic Chemistry, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany

Polymers 2016, 8(12), 435; https://doi.org/10.3390/polym8120435 - 14 Dec 2016

Cited by 29 | Viewed by 9123

Abstract

Photoactuating liquid crystalline elastomers (LCE) are promising candidates for an application as artificial muscles in microdevices. In this work, we demonstrate that by optimizing (1) the illumination conditions and (2) the mixture of azo monomer and azo crosslinker, thick films of an all-azo [...] Read more.

Photoactuating liquid crystalline elastomers (LCE) are promising candidates for an application as artificial muscles in microdevices. In this work, we demonstrate that by optimizing (1) the illumination conditions and (2) the mixture of azo monomer and azo crosslinker, thick films of an all-azo LCE can be prepared, which show a strong length change without bending during photoactuation. This becomes possible by working with white light (about 440 nm), whose absorption is low, leading to a large penetration depth. By adding an azo crosslinker to a previously prepared system, several improvements of the actuation properties—like a stronger photoactuation at lower operational temperatures—could be achieved. In addition, films of different crosslinker concentrations and thicknesses were produced by photopolymerization at varying temperatures within a magnetic field, and their thermo- and photoresponsive behavior was investigated. An extraordinarily strong maximal thermal actuation of 46% and—by exposure to white light at 70 °C—a photoresponsive change in length of up to 40% in just about 13 s could be obtained. Even densely crosslinked samples were still able to photoactuate remarkably. Isothermal back-deformation could either be achieved by irradiation with red light (7 min) or by keeping the film in the dark (13 min). Full article

(This article belongs to the Special Issue Polymeric Soft Actuators)

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16 pages, 5073 KiB

Open AccessArticle

Temperature-, pH- and CO₂-Sensitive Poly(N-isopropylacryl amide-co-acrylic acid) Copolymers with High Glass Transition Temperatures

by Yeong-Tarng Shieh^1,*, Pei-Yi Lin^1,2, Tao Chen³

and Shiao-Wei Kuo^2,*

¹ Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan

² Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan

³ Ningbo Institute of Material Technology and Engineering, Key Laboratory of Graphene Technologies and Applications of Zhejiang Province, Chinese Academy of Science, Zhongguan West Road 1219, Ningbo 315201, China

Polymers 2016, 8(12), 434; https://doi.org/10.3390/polym8120434 - 14 Dec 2016

Cited by 45 | Viewed by 10320

Abstract

A series of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAAm-co-PAA) random copolymers were synthesized through free radical copolymerization in MeOH. The incorporation of the acrylic acid units into PNIPAAm tended to enhance the glass transition temperature (T_g), due [...] Read more.

A series of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAAm-co-PAA) random copolymers were synthesized through free radical copolymerization in MeOH. The incorporation of the acrylic acid units into PNIPAAm tended to enhance the glass transition temperature (T_g), due to strong intermolecular hydrogen bonding between the amide groups of PNIPAAm and the carboxyl groups of PAA, as observed using ¹H nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopic analyses. The lower critical solution temperature (LCST) increased upon increasing the pH of the aqueous solution containing PNIPAAm-co-PAA because the COOH groups of the PAA segment dissociated into COO⁻ groups, enhancing the solubility of the copolymer. In addition, high-pressure differential scanning calorimetry revealed that the LCSTs of all the aqueous solutions of the copolymers decreased upon increasing the pressure of CO₂, suggesting that CO₂ molecules had displaced H₂O molecules around the polar CONH and COOH groups in PNIPAAm-co-PAA, thereby promoting the hydrophobicity of the copolymers in the aqueous solution. In addition, the values of T_g of a film sample increased upon treatment with supercritical CO₂, implying that intermolecular interactions in the copolymer had been enhanced after such treatment. Full article

(This article belongs to the Special Issue Functionally Responsive Polymeric Materials)

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17 pages, 4267 KiB

Open AccessArticle

Dynamic and Static Behavior of Hollow-Core FRP-Concrete-Steel and Reinforced Concrete Bridge Columns under Vehicle Collision

by Omar I. Abdelkarim¹ and Mohamed A. ElGawady^2,*

¹ Civil Engineering Department, University of Sherbrooke, Sherbrooke, QC J1K 2R1, Canada

² Department of Civil, Architectural, and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA

Polymers 2016, 8(12), 432; https://doi.org/10.3390/polym8120432 - 13 Dec 2016

Cited by 15 | Viewed by 6584

Abstract

This paper presents the difference in behavior between hollow-core fiber reinforced polymer-concrete-steel (HC-FCS) columns and conventional reinforced concrete (RC) columns under vehicle collision in terms of dynamic and static forces. The HC-FCS column consisted of an outer FRP tube, an inner steel tube, [...] Read more.

This paper presents the difference in behavior between hollow-core fiber reinforced polymer-concrete-steel (HC-FCS) columns and conventional reinforced concrete (RC) columns under vehicle collision in terms of dynamic and static forces. The HC-FCS column consisted of an outer FRP tube, an inner steel tube, and a concrete shell sandwiched between the two tubes. The steel tube was hollow inside and embedded into the concrete footing with a length of 1.5 times the tube diameter while the FRP tube stopped at the top of footing. The RC column had a solid cross-section. The study was conducted through extensive finite element impact analyses using LS-DYNA software. Nine parameters were studied including the concrete material model, unconfined concrete compressive strength, material strain rate, column height-to-diameter ratio, column diameter, column top boundary condition, axial load level, vehicle velocity, and vehicle mass. Generally, the HC-FCS columns had lower dynamic forces and higher static forces than the RC columns when changing the values of the different parameters. During vehicle collision with either the RC or the HC-FCS columns, the imposed dynamic forces and their equivalent static forces were affected mainly by the vehicle velocity and vehicle mass. Full article

(This article belongs to the Special Issue Selected Papers from “SMAR 2015”)

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12 pages, 4084 KiB

Open AccessArticle

An Investigation of the High Performance of a Novel Type of Benzobisoxazole Fiber Based on 3,3-Diaminobenzidine

by Yang Wang^1,2, Yuanjun Song¹, Lei Zhao¹, Nahla Rahoui¹, Bo Jiang^1,* and Yudong Huang^1,*

¹ MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, China

² College of Chemistry, Chemical Engineering and Materials Science, Heilongjiang University, Harbin 150001, China

Polymers 2016, 8(12), 420; https://doi.org/10.3390/polym8120420 - 13 Dec 2016

Cited by 4 | Viewed by 7194

Abstract

The mechanical and thermal properties of poly{2,6-diimidazo[4,5-b:4′5′-e] pyridinylene-1,4(2,5-dihydroxy) phenylene} (PIPD)-3,3-diaminobenzidine (DAB) fibers were analyzed. Compared to other types of benzimidazole fiber structures and properties, PIPD-DAB is distinguished by a unique combination of strength, tensile modulus, and thermal properties. The PIPD polymer was prepared [...] Read more.

The mechanical and thermal properties of poly{2,6-diimidazo[4,5-b:4′5′-e] pyridinylene-1,4(2,5-dihydroxy) phenylene} (PIPD)-3,3-diaminobenzidine (DAB) fibers were analyzed. Compared to other types of benzimidazole fiber structures and properties, PIPD-DAB is distinguished by a unique combination of strength, tensile modulus, and thermal properties. The PIPD polymer was prepared from 2,3,5,6-tetra-aminopyridine (TAP) and 2,5-dihydroxyterephthalic acid (DHTA) in polyphosphoric acid (PPA). In order to enhance the tensile strength and modulus, a third comonomer, 3,3-diaminobenzidine (DAB), was incorporated into the PIPD molecular structure. The change in molecular structure was recorded using Fourier-transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and wide angle X-ray diffraction (WAXD). Compared to the PIPD fibers (average tensile strength of PIPD is 3.9 GPa, average tensile modulus of PIPD is 287 GPa), the tensile strength and modulus of PIPD-DAB increased to 4.2 and 318 GPa, respectively. In addition, the thermal decomposition temperature of the PIPD fibers is enhanced by 35 °C, due to the incorporated DAB. PIPD-DAB is a promising material for use under high tensile loads and/or high temperatures. Full article

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12 pages, 4143 KiB

Open AccessArticle

The Effect of Thermal History on the Fast Crystallization of Poly(l-Lactide) with Soluble-Type Nucleators and Shear Flow

by Tianfeng Shen, Piming Ma^*, Qingqing Yu, Weifu Dong and Mingqing Chen

The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, 1800 Lihu Road, Wuxi 214122, China

Polymers 2016, 8(12), 431; https://doi.org/10.3390/polym8120431 - 10 Dec 2016

Cited by 8 | Viewed by 6624

Abstract

The N₁,N₁ʹ-(ethane-1,2-diyl)bis(N₂-phenyloxalamide) (OXA) is a soluble-type nucleator with a dissolving temperature of 230 °C in poly(l-lactic acid) (PLLA) matrix. The effect of thermal history and shear flow on the crystallization behavior of the [...] Read more.

The N₁,N₁ʹ-(ethane-1,2-diyl)bis(N₂-phenyloxalamide) (OXA) is a soluble-type nucleator with a dissolving temperature of 230 °C in poly(l-lactic acid) (PLLA) matrix. The effect of thermal history and shear flow on the crystallization behavior of the PLLA/OXA samples was investigated by rheometry, polarized optical microscopy (POM), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and scanning electron microscopy (SEM). The crystallization process of the PLLA/OXA-240 sample (i.e., pre-melted at 240 °C) was significantly promoted by applying a shear flow, e.g., the onset crystallization time (t_onset) of the PLLA at 155 °C was reduced from 1600 to 200 s after shearing at 0.4 rad/s for even as short as 1.0 s, while the crystallinity (X_c) was increased to 40%. Moreover, the t_onset of the PLLA/OXA-240 sample is 60%–80% lower than that of the PLLA/OXA-200 sample (i.e., pre-melted at 200 °C) with a total shear angle of 2 rad, indicating a much higher crystallization rate of the PLLA/OXA-240 sample. A better organization and uniformity of OXA fibrils can be obtained due to a complete pre-dissolution in the PLLA matrix followed by shear and oscillation treatments. The well dispersed OXA fibrils and flow-induced chain orientation are mainly responsible for the fast crystallization of the PLLA/OXA-240 samples. In addition, the shear flow created some disordered α′-form crystals in the PLLA/OXA samples regardless of the thermal history (200 or 240 °C). Full article

(This article belongs to the Special Issue Young Talents in Polymer Science)

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14 pages, 5640 KiB

Open AccessArticle

All-Inorganic Intumescent Nanocoating Containing Montmorillonite Nanoplatelets in Ammonium Polyphosphate Matrix Capable of Preventing Cotton Ignition

by Jenny Alongi^1,*

and Federico Carosio²

¹ Dipartimento di Chimica, Università degli Studi di Milano, Via Golgi 19, 20133 Milano, Italy

² Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, Alessandria site, Viale Teresa Michel 5, 15121 Alessandria, Italy

Polymers 2016, 8(12), 430; https://doi.org/10.3390/polym8120430 - 10 Dec 2016

Cited by 19 | Viewed by 6943

Abstract

In the present manuscript a new concept of completely inorganic intumescent flame retardant nanocoating comprised of sodium montmorillonite nanoplatelets embedded in an ammonium polyphosphate matrix has been investigated using cotton as model substrate. The coating, deposited by multistep adsorption from diluted water-based suspensions/solutions, [...] Read more.

In the present manuscript a new concept of completely inorganic intumescent flame retardant nanocoating comprised of sodium montmorillonite nanoplatelets embedded in an ammonium polyphosphate matrix has been investigated using cotton as model substrate. The coating, deposited by multistep adsorption from diluted water-based suspensions/solutions, homogenously cover each cotton fibers with average thicknesses below 50 nm and add-on up to 5% in weight. Combustion characterization evidences the interesting properties: indeed, the so-treated fabrics reached self-extinguishing during horizontal flame spread tests. Furthermore, when the coating add-on reaches 5%, no ignition has been observed during cone calorimetry tests under 35 kW/m² heat flux. Residue analyses pointed out the formation of an expanded all-inorganic coating capable of greatly improving char formation by exerting barrier function towards volatile release and heat transfer. Full article

(This article belongs to the Special Issue Young Talents in Polymer Science)

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30 pages, 32992 KiB

Open AccessArticle

Microsphere-Based Hierarchically Juxtapositioned Biphasic Scaffolds Prepared from Poly(Lactic-co-Glycolic Acid) and Nanohydroxyapatite for Osteochondral Tissue Engineering

by K. T. Shalumon^1,*, Chialin Sheu¹

, Yi Teng Fong², Han-Tsung Liao² and Jyh-Ping Chen^1,2,3,4,*

¹ Department of Chemical and Materials Engineering, Chang Gung University, Kwei-San, Taoyuan 33302, Taiwan

² Department of Plastic and Reconstructive Surgery and Craniofacial Research Center, Chang Gung Memorial Hospital, Kwei-San, Taoyuan 33305, Taiwan

³ Graduate Institute of Health Industry and Technology, Research Center for Industry of Human Ecology, Chang Gung University of Science and Technology, Kwei-San, Taoyuan 33302, Taiwan

⁴ Department of Materials Engineering, Ming Chi University of Technology, Tai-Shan, New Taipei City 24301, Taiwan

Polymers 2016, 8(12), 429; https://doi.org/10.3390/polym8120429 - 10 Dec 2016

Cited by 22 | Viewed by 9488

Abstract

This study aims to prepare biphasic osteochondral scaffolds based on seamless joining of sintered polymer and polymer/ceramic microspheres for co-culture of chondrocytes and bone marrow stem cells (BMSCs). Poly(lactide-co-glycolide) (PLGA) microspheres and 10% nanohydroxyapatite (nHAP)-incorporated PLGA (PGA/nHAP) microspheres were prepared through [...] Read more.

This study aims to prepare biphasic osteochondral scaffolds based on seamless joining of sintered polymer and polymer/ceramic microspheres for co-culture of chondrocytes and bone marrow stem cells (BMSCs). Poly(lactide-co-glycolide) (PLGA) microspheres and 10% nanohydroxyapatite (nHAP)-incorporated PLGA (PGA/nHAP) microspheres were prepared through the oil-in-water precipitation method. Virgin (V) and composite (C) scaffolds were prepared from 250–500 µm PLGA and PLGA/nHAP microspheres, respectively, while osteochondral (OC) scaffolds were fabricated through the combination of V and C scaffolds. Physico-chemical properties of scaffolds were characterized through microscopic-spectroscopic evaluations. The effect of nHAP in scaffolds was investigated through thermogravimetric analysis and mechanical testing, while surface hydrophobicity was tested through contact angle measurements. Rabbit chondrocytes and BMSCs were used for cell culture, and cell morphology and proliferation were determined from SEM and DNA assays. Alizarin red and Alcian blue stains were used to identify the in vitro bone and cartilage tissue-specific regeneration, while cetylpyridinium chloride was used to quantitatively estimate calcium in mineralized bone. For co-culture in OC scaffolds, BMSCs were first seeded in the bone part of the scaffold and cultured in osteogenic medium, followed by seeding chondrocytes in the cartilage part, and cultured in chondrocyte medium. High cell viability was confirmed from the Live/Dead assays. Actin cytoskeleton organization obtained by DAPI-phalloidin staining revealed proper organization of chondrocytes and BMSCs in OC scaffolds. Immunofluorescent staining of bone (type I collagen and osteocalcin (OCN)) and cartilage marker proteins (type II collagen (COL II)) confirmed cellular behavior of osteoblasts and chondrocytes in vitro. Using an ectopic osteochondral defect model by subcutaneous implantation of co-cultured OC scaffolds in nude mice confirmed cell proliferation and tissue development from gross view and SEM observation. IF staining of OCN and COL II in the bone and cartilage parts of OC scaffolds and tissue-specific histological analysis exhibited a time-dependent tissue re-modeling and confirmed the potential application of the biphasic scaffold in osteochondral tissue engineering. Full article

(This article belongs to the Special Issue Advance of Polymers Applied to Biomedical Applications: Cell Scaffolds)

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12 pages, 5308 KiB

Open AccessArticle

Real-Time Packing Behavior of Core-Shell Silica@Poly(N-isopropylacrylamide) Microspheres as Photonic Crystals for Visualizing in Thermal Sensing

by Karthikeyan Manivannan¹, Yi-Shen Huang², Bohr-Ran Huang³

, Chih-Feng Huang^2,*

and Jem-Kun Chen^1,*

¹ Department of Materials Science and Engineering, National Taiwan University of Science and Technology, 43, Sec 4, Keelung Road, Taipei 106, Taiwan

² Department of Chemical Engineering, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 402, Taiwan

³ Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, National Taiwan University of Science and Technology, 43, Sec 4, Keelung Road, Taipei 106, Taiwan

Polymers 2016, 8(12), 428; https://doi.org/10.3390/polym8120428 - 10 Dec 2016

Cited by 14 | Viewed by 7165

Abstract

We grafted thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes from monodisperse SiO₂ microspheres through surface-initiated atom transfer radical polymerization (SI ATRP) to generate core-shell structured SiO₂@PNIPAM microspheres (SPMs). Regular-sized SPMs dispersed in aqueous solution and packed as photonic crystals (PCs) in [...] Read more.

We grafted thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes from monodisperse SiO₂ microspheres through surface-initiated atom transfer radical polymerization (SI ATRP) to generate core-shell structured SiO₂@PNIPAM microspheres (SPMs). Regular-sized SPMs dispersed in aqueous solution and packed as photonic crystals (PCs) in dry state. Because of the microscale of the SPMs, the packing behavior of the PCs in water can be observed by optical microscopy. By increasing the temperature above the lower critical solution temperature (LCST) of PNIPAM, the reversible swelling and shrinking of the PNIPAM shell resulted in dispersion and precipitation (three-dimensional aggregation) of the SPM in aqueous solution. The SPMs were microdispersed in a water layer to accommodate the aggregation along two dimensions. In the microdispersion, the SPMs are packed as PCs with microscale spacing between SPMs below the LCST. When the temperature is increased above the LCST, the microdispersed PCs exhibited a close-packed arrangement along two dimensions with decreased spacing between SPMs. The change in spacing with increasing temperature above the LCST resulted in a color change from red to blue, which could be observed by the naked eye at an incident angle. Thus, the SPM array could be applied as a visual temperature sensor. Full article

(This article belongs to the Special Issue Polymers for Chemosensing)

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14 pages, 4240 KiB

Open AccessArticle

Polysarcosine-Based Lipids: From Lipopolypeptoid Micelles to Stealth-Like Lipids in Langmuir Blodgett Monolayers

by Benjamin Weber¹, Christine Seidl¹, David Schwiertz¹, Martin Scherer¹, Stefan Bleher², Regine Süss² and Matthias Barz^1,*

¹ Institute of Organic Chemistry, Johannes Gutenberg University of Mainz, Duesbergweg 10-14, 55128 Mainz, Germany

² Department of Pharmaceutical Technology and Biopharmacy, Institute of Pharmaceutical Sciences, Albert Ludwigs University of Freiburg, Sonnenstraße 5, 79104 Freiburg im Breisgau, Germany

Polymers 2016, 8(12), 427; https://doi.org/10.3390/polym8120427 - 9 Dec 2016

Cited by 31 | Viewed by 11413

Abstract

Amphiphiles and, in particular, PEGylated lipids or alkyl ethers represent an important class of non-ionic surfactants and have become key ingredients for long-circulating (“stealth”) liposomes. While poly-(ethylene glycol) (PEG) can be considered the gold standard for stealth-like materials, it is known to be [...] Read more.

Amphiphiles and, in particular, PEGylated lipids or alkyl ethers represent an important class of non-ionic surfactants and have become key ingredients for long-circulating (“stealth”) liposomes. While poly-(ethylene glycol) (PEG) can be considered the gold standard for stealth-like materials, it is known to be neither a bio-based nor biodegradable material. In contrast to PEG, polysarcosine (PSar) is based on the endogenous amino acid sarcosine (N-methylated glycine), but has also demonstrated stealth-like properties in vitro, as well as in vivo. In this respect, we report on the synthesis and characterization of polysarcosine based lipids with C₁₄ and C₁₈ hydrocarbon chains and their end group functionalization. Size exclusion chromatography (SEC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis reveals that lipopeptoids with a degree of polymerization between 10 and 100, dispersity indices around 1.1, and the absence of detectable side products are directly accessible by nucleophilic ring opening polymerization (ROP). The values for the critical micelle concentration for these lipopolymers are between 27 and 1181 mg/L for the ones with C₁₈ hydrocarbon chain or even higher for the C₁₄ counterparts. The lipopolypeptoid based micelles have hydrodynamic diameters between 10 and 25 nm, in which the size scales with the length of the PSar block. In addition, C₁₈PSar₅₀ can be incorporated in 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) monolayers up to a polymer content of 3%. Cyclic compression and expansion of the monolayer showed no significant loss of polymer, indicating a stable monolayer. Therefore, lipopolypeptoids can not only be synthesized under living conditions, but my also provide a platform to substitute PEG-based lipopolymers as excipients and/or in lipid formulations. Full article

(This article belongs to the Special Issue Young Talents in Polymer Science)

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16 pages, 3516 KiB

Open AccessArticle

Hydrodynamic Interactions and Entanglements of Polymer Solutions in Many-Body Dissipative Particle Dynamics

by Xin Yong

Department of Mechanical Engineering, State University of New York at Binghamton, Binghamton, NY 13902, USA

Polymers 2016, 8(12), 426; https://doi.org/10.3390/polym8120426 - 9 Dec 2016

Cited by 23 | Viewed by 10899

Abstract

Using many-body dissipative particle dynamics (MDPD), polymer solutions with concentrations spanning dilute and semidilute regimes are modeled. The parameterization of MDPD interactions for systems with liquid–vapor coexistence is established by mapping to the mean-field Flory–Huggins theory. The characterization of static and dynamic properties [...] Read more.

Using many-body dissipative particle dynamics (MDPD), polymer solutions with concentrations spanning dilute and semidilute regimes are modeled. The parameterization of MDPD interactions for systems with liquid–vapor coexistence is established by mapping to the mean-field Flory–Huggins theory. The characterization of static and dynamic properties of polymer chains is focused on the effects of hydrodynamic interactions and entanglements. The coil–globule transition of polymer chains in dilute solutions is probed by varying solvent quality and measuring the radius of gyration and end-to-end distance. Both static and dynamic scaling relations for polymer chains in poor, theta, and good solvents are in good agreement with the Zimm theory with hydrodynamic interactions considered. Semidilute solutions with polymer volume fractions up to 0.7 exhibit the screening of excluded volume interactions and subsequent shrinking of polymer coils. Furthermore, entanglements become dominant in the semidilute solutions, which inhibit diffusion and relaxation of chains. Quantitative analysis of topology violation confirms that entanglements are correctly captured in the MDPD simulations. Full article

(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)

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19 pages, 13443 KiB

Open AccessArticle

Polyetheretherketone Hybrid Composites with Bioactive Nanohydroxyapatite and Multiwalled Carbon Nanotube Fillers

by Chen Liu¹, Kai Wang Chan¹, Jie Shen², Cheng Zhu Liao³, Kelvin Wai Kwok Yeung² and Sie Chin Tjong^1,*

¹ Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China

² Department of Orthopedics and Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China

³ Department of Materials Science and Engineering, South University of Science and Technology of China, Shenzhen 518055, China

Polymers 2016, 8(12), 425; https://doi.org/10.3390/polym8120425 - 8 Dec 2016

Cited by 44 | Viewed by 7395

Abstract

Polyetheretherketone (PEEK) hybrid composites reinforced with inorganic nanohydroxyapatite (nHA) and multiwalled carbon nanotube (MWNT) were prepared by melt-compounding and injection molding processes. The additions of nHA and MWNT to PEEK were aimed to increase its elastic modulus, tensile strength, and biocompatibility, rendering the [...] Read more.

Polyetheretherketone (PEEK) hybrid composites reinforced with inorganic nanohydroxyapatite (nHA) and multiwalled carbon nanotube (MWNT) were prepared by melt-compounding and injection molding processes. The additions of nHA and MWNT to PEEK were aimed to increase its elastic modulus, tensile strength, and biocompatibility, rendering the hybrids suitable for load-bearing implant applications. The structural behavior, mechanical property, wettability, osteoblastic cell adhesion, proliferation, differentiation, and mineralization of the PEEK/nHA-MWNT hybrids were studied. X-ray diffraction and SEM observation showed that both nHA and MWNT fillers are incorporated into the polymer matrix of PEEK-based hybrids. Tensile tests indicated that the elastic modulus of PEEK can be increased from 3.87 to 7.13 GPa by adding 15 vol % nHA and 1.88 vol % MWNT fillers. The tensile strength and elongation at break of the PEEK/(15% nHA)-(1.88% MWNT) hybrid were 64.48 MPa and 1.74%, respectively. Thus the tensile properties of this hybrid were superior to those of human cortical bones. Water contact angle measurements revealed that the PEEK/(15% nHA)-(1.88% MWNT) hybrid is hydrophilic due to the presence of nHA. Accordingly, hydrophilic PEEK/(15% nHA)-(1.88% MWNT) hybrid promoted the adhesion, proliferation, differentiation, and mineralization of murine MC3T3-E1 osteoblasts on its surface effectively on the basis of cell culture, fluorescence microscopy, MTT assay, WST-1 assay, alkaline phosphatase activity, and Alizarin red staining tests. Thus the PEEK/(15% nHA)-(1.88% MWNT) hybrid has the potential to be used for fabricating load-bearing bone implants. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2016)

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16 pages, 3192 KiB

Open AccessArticle

Isothermal Cold Crystallization, Heat Resistance, and Tensile Performance of Polylactide/Thermoplastic Polyester Elastomer (PLA/TPEE) Blends: Effects of Annealing and Reactive Compatibilizer

by Sisi Wang^1,2, Sujuan Pang^1,2, Lisha Pan^1,2, Nai Xu^1,2,* and Tan Li³

¹ College of Materials and Chemical Engineering, Hainan University, Haikou 570228, China

² Hainan Provincial Fine Chemical Engineering Research Center, Hainan University, Haikou 570228, China

³ Shiner National & Local Joint Engineering & Research Center, Shiner Industrial Co., Ltd., Haikou 570125, China

Polymers 2016, 8(12), 417; https://doi.org/10.3390/polym8120417 - 8 Dec 2016

Cited by 25 | Viewed by 7884

Abstract

The combined influences of crystallinity and reactive compatibilizer—a multifunctional epoxide (ADR)—on morphology, tensile performance, and heat resistance of polylactide/thermoplastic polyester elastomer (PLA/TPEE) (80/20) blends were investigated. Annealing involved an isothermal cold crystallization of PLA matrix was performed to increase crystallinity of the samples. [...] Read more.

The combined influences of crystallinity and reactive compatibilizer—a multifunctional epoxide (ADR)—on morphology, tensile performance, and heat resistance of polylactide/thermoplastic polyester elastomer (PLA/TPEE) (80/20) blends were investigated. Annealing involved an isothermal cold crystallization of PLA matrix was performed to increase crystallinity of the samples. First, isothermal cold crystallization kinetics were investigated using differential scanning calorimetry measurement. It was found that the addition of ADR decreased the crystallization rate of the samples. The maximum crystallinity of the annealed samples also decreased from 40% to 34% while ADR loading increased from zero to 1.0 phr. Furthermore, influence of crystallinity on mechanical performances of the PLA/TPEE sample was researched. The heat resistance of the sample showed a significant enhancement while increasing its crystallinity. Meanwhile, the tensile ductility of the crystallized PLA/TPEE sample became very poor due to the embrittlement with increased crystallinity and the incompatibility between PLA and TPEE. However, the annealed PLA/TPEE/ADR samples with high crystallinity kept a higher tensile ductility because ADR greatly improved the interfacial compatibility. Differences in tensile fracture behaviors of the quenched and annealed PLA/TPEE samples with and without ADR were discussed in detail. At last, crystallized PLA/TPEE/ADR blends with excellent heat resistance and high tensile ductility were obtained by annealing and reactive compatibilization. Full article

(This article belongs to the Special Issue Polymer Blends 2017)

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12 pages, 276 KiB

Open AccessReview

Dynamics of Polymer Translocation: A Short Review with an Introduction of Weakly-Driven Regime

by Takahiro Sakaue^1,2

¹ Department of Physics, Kyushu University, Fukuoka 819-0395, Japan

² Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Honcho Kawaguchi, Saitama 332-0012, Japan

Polymers 2016, 8(12), 424; https://doi.org/10.3390/polym8120424 - 7 Dec 2016

Cited by 37 | Viewed by 5248

Abstract

As emphasized in a recent review (by V.V. Palyulin, T. Ala-Nissila, R. Metzler), theoretical understanding of the unbiased polymer translocation lags behind that of the (strongly) driven translocation. Here, we suggest the introduction of a weakly-driven regime, as described by the linear [...] Read more.

As emphasized in a recent review (by V.V. Palyulin, T. Ala-Nissila, R. Metzler), theoretical understanding of the unbiased polymer translocation lags behind that of the (strongly) driven translocation. Here, we suggest the introduction of a weakly-driven regime, as described by the linear response theory to the unbiased regime, which is followed by the strongly-driven regime beyond the onset of nonlinear response. This provides a concise crossover scenario, bridging the unbiased to strongly-driven regimes. Full article

(This article belongs to the Special Issue Young Talents in Polymer Science)

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16 pages, 5031 KiB

Open AccessArticle

Investigating the Synergistic Effects of Combined Modified Alginates on Macrophage Phenotype

by Hannah C. Bygd¹ and Kaitlin M. Bratlie^1,2,3,*

¹ Department of Materials Science & Engineering, Iowa State University, Ames, IA 50011, USA

² Department of Chemical & Biological Engineering, Iowa State University, Ames, IA 50011, USA

³ Division of Materials Science & Engineering, Ames National Laboratory, Ames, IA 50011, USA

Polymers 2016, 8(12), 422; https://doi.org/10.3390/polym8120422 - 6 Dec 2016

Cited by 12 | Viewed by 5725

Abstract

Understanding macrophage responses to biomaterials is crucial to the success of implanted medical devices, tissue engineering scaffolds, and drug delivery vehicles. Cellular responses to materials may depend synergistically on multiple surface chemistries, due to the polyvalent nature of cell–ligand interactions. Previous work in [...] Read more.

Understanding macrophage responses to biomaterials is crucial to the success of implanted medical devices, tissue engineering scaffolds, and drug delivery vehicles. Cellular responses to materials may depend synergistically on multiple surface chemistries, due to the polyvalent nature of cell–ligand interactions. Previous work in our lab found that different surface functionalities of chemically modified alginate could sway macrophage phenotype toward either the pro-inflammatory or pro-angiogenic phenotype. Using these findings, this research aims to understand the relationship between combined material surface chemistries and macrophage phenotype. Tumor necrosis factor-α (TNF-α) secretion, nitrite production, and arginase activity were measured and used to determine the ability of the materials to alter macrophage phenotype. Cooperative relationships between pairwise modifications of alginate were determined by calculating synergy values for the aforementioned molecules. Several materials appeared to improve M1 to M2 macrophage reprogramming capabilities, giving valuable insight into the complexity of surface chemistries needed for optimal incorporation and survival of implanted biomaterials. Full article

(This article belongs to the Special Issue Young Talents in Polymer Science)

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11 pages, 9907 KiB

Open AccessArticle

Miscibility, Morphology and Crystallization Behavior of Poly(Butylene Succinate-co-Butylene Adipate)/Poly(Vinyl Phenol)/Poly(l-Lactic Acid) Blends

by Pengfei Si^1,2, Faliang Luo^1,2,* and Fahai Luo^1,3

¹ Ministry-Province Co-Cultivated Key Laboratory Base of Natural Gas Conversion, Ningxia University, Yinchuan 750021, China

² School of Chemistry and Chemical Engineering, Ningxia University, Yinchuan 750021, China

³ Teaching and Research Group of Physics, Liupanshan High School of Ningxia, Yinchuan 750002, China

Polymers 2016, 8(12), 421; https://doi.org/10.3390/polym8120421 - 6 Dec 2016

Cited by 10 | Viewed by 5907

Abstract

Amorphous poly(vinyl phenol) (PVPh) is introduced into poly(butylene succinate-co-butylene adipate)/poly(l-lactic acid) (PBSA/PLLA) blends via solution casting. Fourier transform infrared spectroscopy (FTIR) analysis verifies that intermolecular hydrogen bonding formed in PBSA/PVPh/PLLA blends. The miscibility between PBSA and PLLA is improved [...] Read more.

Amorphous poly(vinyl phenol) (PVPh) is introduced into poly(butylene succinate-co-butylene adipate)/poly(l-lactic acid) (PBSA/PLLA) blends via solution casting. Fourier transform infrared spectroscopy (FTIR) analysis verifies that intermolecular hydrogen bonding formed in PBSA/PVPh/PLLA blends. The miscibility between PBSA and PLLA is improved with PVPh incorporation as evidenced by approaching T_gs of the two components. When PVPh content reaches up to 50 wt %, the blend sample exhibits only one T_g, meaning complete miscibility between PBSA and PLLA. The improved miscibility of PBSA/PLLA blends is further confirmed by scanning electron microscope (SEM). Typical “see-island” phase separation structure for PBSA/PLLA blend transforms into homogenous phase structure for blend samples with 5 wt % PVPh and above. Non-isothermal crystallization analysis shows that the crystallization temperature and crystallization enthalpy of PBSA decrease with PVPh addition, and those of PLLA also show a decreasing trend. Isothermal crystallization rate of PBSA in blend samples distinctly decreases with PVPh incorporation, whereas that of PLLA in blend samples increases slightly with PVPh addition. Wide angle X-ray diffraction (WAXD) analysis indicated that PLLA in blend samples remained partly crystallized, while PBSA turned into amorphous state with increasing PVPh contents. Full article

(This article belongs to the Special Issue Polymer Blends 2017)

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18 pages, 2515 KiB

Open AccessArticle

New Flexible Flame Retardant Coatings Based on Siloxane Resin and Ethylene-Vinyl Chloride Copolymer

by Dorota Wesolek^*, Ryszard Gasiorowski, Szymon Rojewski, Judyta Walentowska and Rafał Wojcik

Department of Innovative Biomaterials and Nanotechnologies, Institute of Natural Fibres & Medicinal Plants, Wojska Polskiego 71b, 60-630 Poznan, Poland

Polymers 2016, 8(12), 419; https://doi.org/10.3390/polym8120419 - 2 Dec 2016

Cited by 9 | Viewed by 9455

Abstract

This work presents the effectiveness of a phosphorus-containing flame retardant based on siloxane resin and ethylene-vinyl chloride copolymer as a back-coating of fabrics. The possibility of improving flame retardant efficiency of this composition by introducing fumed silica, montmorillonite, carbon nanotubes, and graphite was [...] Read more.

This work presents the effectiveness of a phosphorus-containing flame retardant based on siloxane resin and ethylene-vinyl chloride copolymer as a back-coating of fabrics. The possibility of improving flame retardant efficiency of this composition by introducing fumed silica, montmorillonite, carbon nanotubes, and graphite was evaluated. The effect of each additive on the efficiency of the composition was examined separately. Flammability tests of flame retardant-coated fabrics (natural and synthetic) were carried out using pyrolysis combustion flow calorimetry (PCFC), cone calorimetry, and limiting oxygen index determination. An assessment of the ignitability of upholstered furniture containing flame retardant fabric, resistance to washing, antifungal activity, and some of the utility properties of the final newly-developed flame-retardant coating was conducted. Full article

(This article belongs to the Special Issue Recent Advances in Flame Retardancy of Textile Related Products)

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20 pages, 9422 KiB

Open AccessArticle

Hydrogel Layers on the Surface of Polyester-Based Materials for Improvement of Their Biointeractions and Controlled Release of Proteins

by Viktor Korzhikov-Vlakh¹, Maria Krylova¹, Ekaterina Sinitsyna², Elena Ivankova²

, Ilia Averianov² and Tatiana B. Tennikova^1,*

¹ Institute of Chemistry, St. Petersburg State University, Universitetskii Pr. 26, Peterhoff, 198504 St. Petersburg, Russia

² Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoy Pr. 31, 199004 St. Petersburg, Russia

Polymers 2016, 8(12), 418; https://doi.org/10.3390/polym8120418 - 2 Dec 2016

Cited by 24 | Viewed by 7096

Abstract

The modification of bioresorbable polyester surfaces in order to alter their biointeractions presents an important problem in biomedical polymer science. In this study, the covalent modification of the surface of poly(lactic acid)-based (PLA-based) films with poly(acryl amide) and sodium alginate hydrogels was performed [...] Read more.

The modification of bioresorbable polyester surfaces in order to alter their biointeractions presents an important problem in biomedical polymer science. In this study, the covalent modification of the surface of poly(lactic acid)-based (PLA-based) films with poly(acryl amide) and sodium alginate hydrogels was performed to change the non-specific polyester interaction with proteins and cells, as well as to make possible the covalent attachment of low-molecular weight ligands and to control protein release. The effect of such modification on the film surface properties was studied. Parameters such as swelling, water contact angle, surface area, and binding capacity of low-molecular weight substances were evaluated and compared. The comparative study of adsorption of model protein (BSA) on the surface of non-modified and modified films was investigated and the protein release was evaluated. Cell viability on the surface of hydrogel-coated films was also tested. The developed approach could be applied for the modification of PLA-based scaffolds for tissue engineering and will be further studied for molecular-imprinting of biomolecules on the surface of polyester-based materials for control of biointeractions. Full article

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17 pages, 2838 KiB

Open AccessArticle

Nanoclays for Lipase Immobilization: Biocatalyst Characterization and Activity in Polyester Synthesis

by Hale Öztürk^1,2, Eric Pollet^1,*

, Vincent Phalip¹, Yüksel Güvenilir² and Luc Avérous^1,*

¹ BioTeam/ICPEES-ECPM, UMR 7515, Université de Strasbourg, 25 rue Becquerel, 67087 Strasbourg, Cedex 2, France

² Department of Chemical Engineering, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey

Polymers 2016, 8(12), 416; https://doi.org/10.3390/polym8120416 - 1 Dec 2016

Cited by 24 | Viewed by 5641

Abstract

The immobilization of Candida antarctica lipase B (CALB) was performed by physical adsorption on both neat and organo-modified forms of sepiolite and montmorillonite. The influence of different parameters, e.g., solvent, enzyme loading, cross-linking, and type of clay support, on immobilization efficiency and catalyst [...] Read more.

The immobilization of Candida antarctica lipase B (CALB) was performed by physical adsorption on both neat and organo-modified forms of sepiolite and montmorillonite. The influence of different parameters, e.g., solvent, enzyme loading, cross-linking, and type of clay support, on immobilization efficiency and catalyst hydrolytic activity has been investigated. The highest hydrolytic activities were obtained for CALB immobilized on organo-modified clay minerals, highlighting the beneficial effect of organo-modification. The esterification activity of these CALB/organoclay catalysts was also tested in the ring-opening polymerization of ε-caprolactone. The polymerization kinetics observed for clay-immobilized catalysts confirmed that CALB adsorbed on organo-modified montmorillonite (CALB/MMTMOD) was the highest-performing catalytic system. Full article

(This article belongs to the Special Issue Enzymatic Polymer Synthesis)

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12 pages, 2619 KiB

Open AccessArticle

Characterization of Epoxy Composites Reinforced with Wax Encapsulated Microcrystalline Cellulose

by Yuanfeng Pan^1,2, Ying Pan³, Qingzheng Cheng¹, Yi Liu⁴, Charles Essien¹, Brian Via^1,*, Xiaoying Wang², Runcang Sun^2,* and Steven Taylor⁵

¹ Forest Products Development Center, School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36849, USA

² State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China

³ College of Chemical Science and Engineering, Qingdao University, Qingdao 266071, China

⁴ College of Material Science and Technology, Beijing Forestry University, Beijing 100083, China

⁵ Department of Biosystems Engineering, Auburn University, Auburn, AL 36849, USA

Polymers 2016, 8(12), 415; https://doi.org/10.3390/polym8120415 - 30 Nov 2016

Cited by 16 | Viewed by 7991

Abstract

The effect of paraffin wax encapsulated microcrystalline cellulose (EMC) particles on the mechanical and physical properties of EMC/epoxy composites were investigated. It was demonstrated that the compatibility between cellulose and epoxy resin could be maintained due to partial encapsulation resulting in an improvement [...] Read more.

The effect of paraffin wax encapsulated microcrystalline cellulose (EMC) particles on the mechanical and physical properties of EMC/epoxy composites were investigated. It was demonstrated that the compatibility between cellulose and epoxy resin could be maintained due to partial encapsulation resulting in an improvement in epoxy composite mechanical properties. This work was unique because it was possible to improve the physical and mechanical properties of the EMC/epoxy composites while encapsulating the microcrystalline cellulose (MCC) for a more homogeneous dispersion. The addition of EMC could increase the stiffness of epoxy composites, especially when the composites were wet. The 1% EMC loading with a 1:2 ratio of wax:MCC demonstrated the best reinforcement for both dry and wet properties. The decomposition temperature of epoxy was preserved up to a 5% EMC loading and for different wax:MCC ratios. An increase in wax encapsulated cellulose loading did increase water absorption but overall this absorption was still low (<1%) for all composites. Full article

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9 pages, 4488 KiB

Open AccessArticle

Intrinsic Delocalization during the Decay of Excitons in Polymeric Solar Cells

by Weikang Chen¹, Deyao Jiang^1,2, Renai Chen^1,2, Sheng Li^1,2,3,* and Thomas F. George^3,*

¹ Department of Physics, Zhejiang Normal University, Jinhua 321004, Zhejiang, China

² Department of Physics, Fudan University, Shanghai 200433, China

³ Office of the Chancellor and Center for Nanoscience, Departments of Chemistry & Biochemistry and Physics & Astronomy, University of Missouri–St. Louis, St. Louis, MO 63121, USA

Polymers 2016, 8(12), 414; https://doi.org/10.3390/polym8120414 - 30 Nov 2016

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Abstract

In bulk heterojunction polymer solar cells, external photoexcitation results in localized excitons in the polymer chain. After hot exciton formation and subsequent relaxation, the dipole moment drives the electron to partially transfer to extended orbitals from the original localized ones, leading to self-delocalization. [...] Read more.

In bulk heterojunction polymer solar cells, external photoexcitation results in localized excitons in the polymer chain. After hot exciton formation and subsequent relaxation, the dipole moment drives the electron to partially transfer to extended orbitals from the original localized ones, leading to self-delocalization. Based on the dynamic fluorescence spectra, the delocalization of excitons is revealed to be an intrinsic property dominated by exciton decay, acting as a bridge for the exciton to diffuse in the polymeric solar cell. The modification of the dipole moment enhances the efficiency of polymer solar cells. Full article

(This article belongs to the Special Issue Conjugated Polymers 2016)

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Polymers, Volume 8, Issue 12 (December 2016) – 36 articles

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