Polymers

9 pages, 5123 KiB

Open AccessArticle

Physico-Chemical Properties of Soybean Meal-Based Adhesives Reinforced by Ethylene Glycol Diglycidyl Ether and Modified Nanocrystalline Cellulose

by Xiaona Li¹, Mingsong Chen¹, Jizhi Zhang², Qiang Gao¹, Shifeng Zhang^1,* and Jianzhang Li^1,*

¹ Ministry of Education (MOE) Key Laboratory of Wooden Material Science and Application, Beijing Key Laboratory of Wood Science and Engineering, School of Materials Science and Technology, Beijing Forestry University, Beijing 100083, China

² Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (MOE), School of Materials Science and Engineering, Shandong University, Jinan 250061, China

Polymers 2017, 9(9), 463; https://doi.org/10.3390/polym9090463 - 20 Sep 2017

Cited by 30 | Viewed by 10165

Abstract

An eco-friendly soybean meal-based adhesive (SM adhesive) was developed by incorporating ethylene glycol diglycidyl ether (EGDE) and nanocrystalline cellulose (NCC). In order to introduce epoxy groups, NCC was modified by KH560 (denoted as MNCC). The functional groups, thermal stability, and cross section of [...] Read more.

An eco-friendly soybean meal-based adhesive (SM adhesive) was developed by incorporating ethylene glycol diglycidyl ether (EGDE) and nanocrystalline cellulose (NCC). In order to introduce epoxy groups, NCC was modified by KH560 (denoted as MNCC). The functional groups, thermal stability, and cross section of the resultant adhesive were characterized. Three-ply plywood was fabricated to measure the dry and wet shear strength of the adhesive. The experimental results showed that the epoxy groups on MNCC reacted with the carboxyl group of SM protein molecules, forming a crosslinking network and a ductile adhesive layer. As a result, compared with the SM adhesive modified by EGDE, the thermal stability of the adhesive with MNCC was improved and the wet shear strength was increased to 1.08 MPa. Full article

(This article belongs to the Collection Polysaccharides)

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16 pages, 3982 KiB

Open AccessArticle

Photochromic Polyurethanes Showing a Strong Change of Transparency and Refractive Index

by Luca Oggioni^1,2, Chiara Toccafondi³, Giorgio Pariani¹, Letizia Colella^1,2, Maurizio Canepa³

, Chiara Bertarelli^2,4 and Andrea Bianco^1,*

¹ INAF—Osservatorio Astronomico di Brera, via Bianchi 46, 23807 Merate, Italy

² Dipartimento di Chimica, Materiali ed Ingegneria Chimica, Politecnico di Milano, p.zza L. Da Vinci 32, 20133 Milano, Italy

³ OPTMATLAB, Dipartimento di Fisica, Università degli Studi di Genova, Via Dodecaneso 33, 16146 Genova, Italy

⁴ Center for Nano Science and Technology, @PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Italy

Polymers 2017, 9(9), 462; https://doi.org/10.3390/polym9090462 - 20 Sep 2017

Cited by 16 | Viewed by 7717

Abstract

Photochromic polymers have been studied as rewritable systems for optical elements with tunable transparency in the visible and refractive index in the NIR. Six diarylethene monomers have been synthesized to give thin films of photochromic polyurethanes. The absorption properties of the monomers in [...] Read more.

Photochromic polymers have been studied as rewritable systems for optical elements with tunable transparency in the visible and refractive index in the NIR. Six diarylethene monomers have been synthesized to give thin films of photochromic polyurethanes. The absorption properties of the monomers in solution and of the corresponding polymeric films have been evaluated showing that a transparency contrast in the visible spectrum of the order of

10^{3}

can be obtained by a suitable choice of the chemical structure and illumination wavelength. The change in the refractive index in the NIR have been determined by ellipsometry showing changes larger than

10^{- 2}

. A trend of this variation with the absorption properties has been also highlighted. Fresnel lenses working on the basis of both a change of the transparency and the refractive index (amplitude and phase) have been demonstrated. Full article

(This article belongs to the Special Issue Photo-Responsive Polymers)

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13 pages, 10394 KiB

Open AccessArticle

The Impotence of Non-Brownian Particles on the Gel Transition of Colloidal Suspensions

by Samantha L. Morelly, Maureen H. Tang

and Nicolas J. Alvarez^*

Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA

Polymers 2017, 9(9), 461; https://doi.org/10.3390/polym9090461 - 19 Sep 2017

Cited by 9 | Viewed by 5671

Abstract

The ability to predict transitions in the microstructure of mixed colloidal suspensions is of extreme interest and importance. The data presented here is specific to the case of battery electrode slurries whereby the carbon additive is reported to form strong colloidal gels. Using [...] Read more.

The ability to predict transitions in the microstructure of mixed colloidal suspensions is of extreme interest and importance. The data presented here is specific to the case of battery electrode slurries whereby the carbon additive is reported to form strong colloidal gels. Using rheology, we have determined the effect of mixed particle systems on the critical gel transition

ϕ_{gel}

. More specifically, we show that the introduction of a high volume fraction of large non-Brownian particles has little to no effect on

ϕ_{gel}

. Although

ϕ_{gel}

is unchanged, the larger particles do change the shape of the linear viscoelasticity and the nonlinear yielding behavior. There are interesting similarities to the nonlinear behavior of the colloidal gels with trends observed for colloidal glasses. A comparison of experimental data and the prediction from theory shows that the equation presented by Poon et al. is able to quantitatively predict the transition from a fluid state to a gel state. Full article

(This article belongs to the Special Issue Complex Fluid Rheology)

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12 pages, 5434 KiB

Open AccessArticle

Catalyst System for Hydrogenation Catalysis Based on Multiarm Hyperbranched Polymer Templated Metal (Au, Pt, Pd, Cu) Nanoparticles

by Yunfeng Shi^1,2,*, Lixin Liu^1,2, Fengyue Zhang¹, Mengyuan Niu¹, Yanzhu Zhao¹, Yifan Fan¹, Yanping Liang¹, Mei Liu¹, Zhenzhu Zhang¹ and Junjie Wang^1,2,*

¹ School of Chemistry and Chemical Engineering, Anyang Normal University, Anyang 455000, China

² Henan Province Key Laboratory of New Optoelectronic Functional Materials, Anyang Normal University, Anyang 455000, China

Polymers 2017, 9(9), 459; https://doi.org/10.3390/polym9090459 - 19 Sep 2017

Cited by 15 | Viewed by 5559

Abstract

With a hyperbranched poly(amidoamine) core and many water-soluble poly(ethylene glycol) monomethyl ether arms connected by pH-sensitive acylhydrazone bonds, multiarm hyperbranched polymer was used as nanoreactor and reductant to prepare metal nanoparticles endowed with intelligence and biocompatibility. The multiarm hyperbranched polymer encapsulated nanoparticles (NPs) [...] Read more.

With a hyperbranched poly(amidoamine) core and many water-soluble poly(ethylene glycol) monomethyl ether arms connected by pH-sensitive acylhydrazone bonds, multiarm hyperbranched polymer was used as nanoreactor and reductant to prepare metal nanoparticles endowed with intelligence and biocompatibility. The multiarm hyperbranched polymer encapsulated nanoparticles (NPs) showed excellent catalytic activity for hydrogenation, thus an excellent catalyst system for hydrogenation was established. The rate constants could reach as high as 3.48 L·s⁻¹·m⁻², which can be attributed to the lack of surface passivation afforded by the multiarm hyperbranched polymer. Full article

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14 pages, 2927 KiB

Open AccessArticle

Bioconversion of Waste Fiber Sludge to Bacterial Nanocellulose and Use for Reinforcement of CTMP Paper Sheets

by Genqiang Chen^1,2, Guochao Wu²

, Björn Alriksson³, Wei Wang¹, Feng F. Hong^1,*

and Leif J. Jönsson^2,*

¹ College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, China

² Department of Chemistry, Umeå University, Umeå SE-901 87, Sweden

³ RISE Processum AB, SE-891 22 Örnsköldsvik, Sweden

Polymers 2017, 9(9), 458; https://doi.org/10.3390/polym9090458 - 18 Sep 2017

Cited by 36 | Viewed by 8996

Abstract

Utilization of bacterial nanocellulose (BNC) for large-scale applications is restricted by low productivity in static cultures and by the high cost of the medium. Fiber sludge, a waste stream from pulp and paper mills, was enzymatically hydrolyzed to sugar, which was used for [...] Read more.

Utilization of bacterial nanocellulose (BNC) for large-scale applications is restricted by low productivity in static cultures and by the high cost of the medium. Fiber sludge, a waste stream from pulp and paper mills, was enzymatically hydrolyzed to sugar, which was used for the production of BNC by the submerged cultivation of Komagataeibacter xylinus. Compared with a synthetic glucose-based medium, the productivity of purified BNC from the fiber sludge hydrolysate using shake-flasks was enhanced from 0.11 to 0.17 g/(L × d), although the average viscometric degree of polymerization (DP_v) decreased from 6760 to 6050. The cultivation conditions used in stirred-tank reactors (STRs), including the stirring speed, the airflow, and the pH, were also investigated. Using STRs, the BNC productivity in fiber-sludge medium was increased to 0.32 g/(L × d) and the DP_v was increased to 6650. BNC produced from the fiber sludge hydrolysate was used as an additive in papermaking based on the chemithermomechanical pulp (CTMP) of birch. The introduction of BNC resulted in a significant enhancement of the mechanical strength of the paper sheets. With 10% (w/w) BNC in the CTMP/BNC mixture, the tear resistance was enhanced by 140%. SEM images showed that the BNC cross-linked and covered the surface of the CTMP fibers, resulting in enhanced mechanical strength. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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15 pages, 13995 KiB

Open AccessArticle

A Wearable and Wireless Gas-Sensing System Using Flexible Polymer/Multi-Walled Carbon Nanotube Composite Films

by Jin-Chern Chiou^1,2 and Chin-Cheng Wu^1,*

¹ Department of Electrical Engineering, National Chiao Tung University, 1001 University Road, Hsinchu City 30010, Taiwan

² Institute of Electrical and Control Engineering, National Chiao Tung University, 1001 University Road, Hsinchu City 30010, Taiwan

Polymers 2017, 9(9), 457; https://doi.org/10.3390/polym9090457 - 18 Sep 2017

Cited by 21 | Viewed by 7420

Abstract

In this study, an integrated flexible gas sensor was developed based on a polymer/multi-walled carbon nanotube composite film by using Bluetooth wireless communication/interface technology. Polymer/multi-walled carbon nanotube composite films were deposited over a polyimide flexible substrate for building a gas sensor array by [...] Read more.

In this study, an integrated flexible gas sensor was developed based on a polymer/multi-walled carbon nanotube composite film by using Bluetooth wireless communication/interface technology. Polymer/multi-walled carbon nanotube composite films were deposited over a polyimide flexible substrate for building a gas sensor array by using a drop-casting method. Sensor response was acquired through interdigitated electrodes and multi-channel sensor boards, which were linked to a Bluetooth wireless transceiver. Additionally, a double-spiral-shaped heater was built into the backside of the gas sensor array as a thermostat to protect it from the influence of ambient temperature. Multi-channel sensing responses were read on a display screen via a smartphone application (app). The advantages of this system include light weight, low cost, highly integrated sensors, wireless telecommunication, and real-time functioning. Thus, it is a promising candidate for deployment in a wearable gas-sensing system used to study air pollution. Full article

(This article belongs to the Special Issue Wearable Sensor)

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13 pages, 2846 KiB

Open AccessArticle

Thermally Stable Bulk Heterojunction Prepared by Sequential Deposition of Nanostructured Polymer and Fullerene

by Heewon Hwang¹, Hoyeon Lee², Shafidah Shafian¹, Wooseop Lee², Jeesoo Seok¹, Ka Yeon Ryu¹, Du Yeol Ryu² and Kyungkon Kim^1,*

¹ Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea

² Department of Chemical and Bimolecular Engineering, Yonsei University, Seoul 03722, Korea

Polymers 2017, 9(9), 456; https://doi.org/10.3390/polym9090456 - 17 Sep 2017

Cited by 26 | Viewed by 6951

Abstract

A morphologically-stable polymer/fullerene heterojunction has been prepared by minimizing the intermixing between polymer and fullerene via sequential deposition (SqD) of a polymer and a fullerene solution. A low crystalline conjugated polymer of PCPDTBT (poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]) has been utilized for the polymer layer and [...] Read more.

A morphologically-stable polymer/fullerene heterojunction has been prepared by minimizing the intermixing between polymer and fullerene via sequential deposition (SqD) of a polymer and a fullerene solution. A low crystalline conjugated polymer of PCPDTBT (poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]) has been utilized for the polymer layer and PC₇₁BM (phenyl-C₇₁-butyric-acid-methyl ester) for the fullerene layer, respectively. Firstly, a nanostructured PCPDTBT bottom layer was developed by utilizing various additives to increase the surface area of the polymer film. The PC₇₁BM solution was prepared by dissolving it in the 1,2-dichloroethane (DCE), exhibiting a lower vapor pressure and slower diffusion into the polymer layer. The deposition of the PC₇₁BM solution on the nanostructured PCPDTBT layer forms an inter-digitated bulk heterojunction (ID-BHJ) with minimized intermixing. The organic photovoltaic (OPV) device utilizing the ID-BHJ photoactive layer exhibits a highly reproducible solar cell performance. In spite of restricted intermixing between the PC₇₁BM and the PCPDTBT, the efficiency of ID-BHJ OPVs (3.36%) is comparable to that of OPVs (3.87%) prepared by the conventional method (deposition of a blended solution of polymer:fullerene). The thermal stability of the ID-BHJ is superior to the bulk heterojunction (BHJ) prepared by the conventional method. The ID-BHJ OPV maintains 70% of its initial efficiency after thermal stress application for twelve days at 80 °C, whereas the conventional BHJ OPV maintains only 40% of its initial efficiency. Full article

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13 pages, 4157 KiB

Open AccessArticle

Two-Sided Surface Oxidized Cellulose Membranes Modified with PEI: Preparation, Characterization and Application for Dyes Removal

by Wei Wang^*, Qian Bai, Tao Liang, Huiyu Bai and Xiaoya Liu

Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, China

Polymers 2017, 9(9), 455; https://doi.org/10.3390/polym9090455 - 16 Sep 2017

Cited by 32 | Viewed by 7668

Abstract

Porous regenerated cellulose (RC) membranes were prepared with cotton linter pulp as a raw material. These membranes were first oxidized on both sides by a modified (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation system using a controlled oxidation reaction technique. Then, the oxidized RC membranes were functionalized

[...] Read more.

Porous regenerated cellulose (RC) membranes were prepared with cotton linter pulp as a raw material. These membranes were first oxidized on both sides by a modified (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation system using a controlled oxidation reaction technique. Then, the oxidized RC membranes were functionalized with polyethylenimine (PEI) via the glutaraldehyde crosslinking method to obtain bifunctional (carboxyl and amino) porous RC membranes, as revealed by Fourier transform infrared spectroscopy (FT-IR), elemental analysis and zeta potential measurement. The scanning electron microscopy (SEM) and the tests of the mechanical properties and permeability characteristics of modified RC membranes demonstrated that the porous structure and certain mechanical properties could be retained. The adsorption performance of the modified membranes towards dyes was subsequently investigated. The modified membranes displayed good adsorption capacities, rapid adsorption equilibrium and removal efficiencies towards both anionic (xylenol orange (XO)) and cationic (methylene blue (MB)) dyes, making them suitable bioadsorbents for wastewater treatment.

Full article

(This article belongs to the Special Issue Polymers from Renewable Resources)

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20 pages, 16690 KiB

Open AccessReview

To Tie or Not to Tie? That Is the Question

by Pawel Dabrowski-Tumanski^1,2

and Joanna I. Sulkowska^1,2,*

¹ Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland

² Faculty of Chemistry, University of Warsaw, Warsaw 02-093, Poland

Polymers 2017, 9(9), 454; https://doi.org/10.3390/polym9090454 - 16 Sep 2017

Cited by 50 | Viewed by 10036

Abstract

In this review, we provide an overview of entangled proteins. Around 6% of protein structures deposited in the PBD are entangled, forming knots, slipknots, lassos and links. We present theoretical methods and tools that enabled discovering and classifying such structures. We discuss the [...] Read more.

In this review, we provide an overview of entangled proteins. Around 6% of protein structures deposited in the PBD are entangled, forming knots, slipknots, lassos and links. We present theoretical methods and tools that enabled discovering and classifying such structures. We discuss the advantages and disadvantages of the non-trivial topology in proteins, based on available data about folding, stability, biological properties and evolutionary conservation. We also formulate intriguing and challenging questions on the border of biophysics, bioinformatics, biology and mathematics, which arise from the discovery of an entanglement in proteins. Finally, we discuss possible applications of entangled proteins in medicine and nanotechnology, such as the chance to design super stable proteins, whose stability could be controlled by chemical potential. Full article

(This article belongs to the Special Issue Knotted and Catenated Polymers)

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12 pages, 4667 KiB

Open AccessArticle

Preparation of Electrospun Nanocomposite Nanofibers of Polyaniline/Poly(methyl methacrylate) with Amino-Functionalized Graphene

by Hanan Abdali^1,2 and Abdellah Ajji^1,*

¹ CREPEC, Department of Chemical Engineering, Polytechnique Montréal, P.O. Box 6079, Station Centre-Ville, Montreal, QC H3C 3A7, Canada

² Ministry of Higher Education, P.O. Box 225085, Riyadh 11153, Saudi Arabia

Polymers 2017, 9(9), 453; https://doi.org/10.3390/polym9090453 - 16 Sep 2017

Cited by 55 | Viewed by 10659

Abstract

In this paper we report upon the preparation and characterization of electrospun nanofibers of doped polyaniline (PANI)/poly(methyl methacrylate) (PMMA)/amino-functionalized graphene (Am-rGO) by electrospinning technique. The successful functionalization of rGO with amino groups is examined by Fourier transforms infrared (FTIR), X-ray photoelectron spectroscopy (XPS) [...] Read more.

In this paper we report upon the preparation and characterization of electrospun nanofibers of doped polyaniline (PANI)/poly(methyl methacrylate) (PMMA)/amino-functionalized graphene (Am-rGO) by electrospinning technique. The successful functionalization of rGO with amino groups is examined by Fourier transforms infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and Raman microspectrometer. The strong electric field enables the liquid jet to be ejected faster and also contributes to the improved thermal and morphological homogeneity of PANI/PMMA/Am-rGO. This results in a decrease in the average diameter of the produced fibers and shows that these fibers can find promising uses in many applications such as sensors, flexible electronics, etc. Full article

(This article belongs to the Special Issue Graphene-Polymer Composites)

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14 pages, 5242 KiB

Open AccessArticle

Effect of the Grafting Reaction of Aluminum Nitride on the Multi-Walled Carbon Nanotubes on the Thermal Properties of the Poly(phenylene sulfide) Composites

by Myounguk Kim^1,2, Sunmin Park^2,* and Jongshin Park^1,*

¹ Department of Biosystems & Biomaterials Science and Engineering, Seoul National University, Seoul 08826, Korea

² Ceramic Fiber & Composite Center, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Korea

Polymers 2017, 9(9), 452; https://doi.org/10.3390/polym9090452 - 15 Sep 2017

Cited by 17 | Viewed by 7000

Abstract

In this study, the PPS/MWCNTs/AlN composite was prepared with poly(phenylene sulfide) (PPS), covalent functionalized multi-walled carbon nanotubes (fMWCNTs), and aluminum nitride (AlN) via melt-blending techniques. The AlN is a fascinating non-oxidizing ceramic material having the highest thermal conductivity among the ceramic materials. In [...] Read more.

In this study, the PPS/MWCNTs/AlN composite was prepared with poly(phenylene sulfide) (PPS), covalent functionalized multi-walled carbon nanotubes (fMWCNTs), and aluminum nitride (AlN) via melt-blending techniques. The AlN is a fascinating non-oxidizing ceramic material having the highest thermal conductivity among the ceramic materials. In order to introduce the functional groups on the surface of the AlN particles, a silane coupling agent was used as it is able to graft with the functional groups on the covalent functionalized MWCNTs. The silanization reaction of the AlN was confirmed qualitatively and quantitatively by FT-IR (Fourier Transform Infrared Spectroscopy), and XPS (X-ray Photoelectron Spectroscopy). The grafting reaction of the AlN particles on the MWCNTs was confirmed using UV–Vis (Ultraviolet-Visible Spectroscopy), FE-SEM (Field-Emission Scanning Electron Microscopy) and FE-TEM (Field-Emission Transmission Electron Microscopy) images. The grafting reaction was accomplished by observing the change of the transmittance, the morphology of the AlN particle bonded to the MWCNTs. For the morphological changes of the fractured surface of the PPS/MWCNTs/AlN composites by FE-SEM, the hybrid filler was homogeneously dispersed on the PPS matrix when the AlN particle was grafted on the MWCNTs. The homogeneous distribution of the hybrid filler acts as a heat transfer path, which led the higher thermal properties, such as thermal conductivity, thermal resistance, and melting temperature than those of not grafted MWCNTs. Full article

(This article belongs to the Special Issue Polymer Nanocomposites)

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19 pages, 30984 KiB

Open AccessArticle

Mixed Rigid and Flexible Component Design for High-Performance Polyimide Films

by Xiaohui Yu, Weihua Liang, Jianhua Cao

and Dayong Wu^*

Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China

Polymers 2017, 9(9), 451; https://doi.org/10.3390/polym9090451 - 15 Sep 2017

Cited by 52 | Viewed by 11608

Abstract

To develop the polyimide (PI) which is closely matched to the coefficient of the thermal expansion (CTE) of copper, a series of PIs are prepared from 5,4′-diamino-2-phenyl benzimidazole (DAPBI), 4,4′-diaminodiphenyl ether (ODA), and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) using a sequential copolymerization, blade coating, and [...] Read more.

To develop the polyimide (PI) which is closely matched to the coefficient of the thermal expansion (CTE) of copper, a series of PIs are prepared from 5,4′-diamino-2-phenyl benzimidazole (DAPBI), 4,4′-diaminodiphenyl ether (ODA), and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) using a sequential copolymerization, blade coating, and thermal imidization process. The physical properties of the PIs are effectively regulated and optimized by adjusting the ratio of the rigid DAPBI and flexible ODA components. By increasing the DAPBI content, thermal stability, dimensional stability, and mechanical properties, the resultant polymer is enhanced. PI-80 exhibits an excellent comprehensive performance, a glass transition temperature of 370 °C, and a tensile strength of 210 MPa. Furthermore, the CTE as calculated in the range 50–250 °C is ca. 19 ppm/K, which is equal to that of copper. A highly dimensionally stable, curl-free, and high T-style peel strength (6.4 N/cm) of copper/PI laminate was obtained by casting the polyamic acid onto copper foil (13 μm) and thermally curing at 360 °C, which indicates that it has the potential to be applied as an electronic film for flexible displays and flexible printed circuit boards. A structural rationalization for these remarkable properties is also presented. Full article

(This article belongs to the Special Issue Processing-Structure-Properties Relationships in Polymers)

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16 pages, 11811 KiB

Open AccessArticle

Osteogenesis of Adipose-Derived and Bone Marrow Stem Cells with Polycaprolactone/Tricalcium Phosphate and Three-Dimensional Printing Technology in a Dog Model of Maxillary Bone Defects

by Jeong Woo Lee¹, Seung Gyun Chu¹, Hak Tae Kim¹, Kang Young Choi¹, Eun Jung Oh^1,2, Jin-Hyung Shim³, Won-Soo Yun³, Jung Bo Huh⁴, Sung Hwan Moon⁵, Seong Soo Kang⁶ and Ho Yun Chung^1,2,*

¹ Department of Plastic and Reconstructive Surgery, School of Medicine, Kyungpook National University, Daegu 41944, Korea

² Cell & Matrix Research Institute, School of Medicine, Kyungpook National University, Daegu 41944, Korea

³ Department of Mechanical Engineering, Korea Polytechnic University, Siheung-Si 15073, Korea

⁴ Department of Prosthodontics, Dental Research Institute, Institute of Translational Dental Science, School of Dentistry, Pusan National University, Yangsan-Si 50612, Korea

⁵ Department of Medicine, School of Medicine, Konkuk University, Seoul 05029, Korea

⁶ College of Veterinary Medicine, Chonnam National University, Gwangju 61186, Korea

Polymers 2017, 9(9), 450; https://doi.org/10.3390/polym9090450 - 15 Sep 2017

Cited by 28 | Viewed by 7572

Abstract

Bone graft material should possess sufficient porosity and permeability to allow integration with native tissue and vascular invasion, and must satisfy oxygen and nutrient transport demands. In this study, we have examined the use of three-dimensional (3D)-printed polycaprolactone/tricalcium phosphate (PCL/TCP) composite material in [...] Read more.

Bone graft material should possess sufficient porosity and permeability to allow integration with native tissue and vascular invasion, and must satisfy oxygen and nutrient transport demands. In this study, we have examined the use of three-dimensional (3D)-printed polycaprolactone/tricalcium phosphate (PCL/TCP) composite material in bone grafting, to estimate the scope of its potential application in bone surgery. Adipose-derived stem cells (ADSCs) and bone marrow stem cells (BMSCs) are known to enhance osteointegration. We hypothesized that a patient-specific 3D-printed solid scaffold could help preserve seeded ADSCs and BMSCs and enhance osteointegration. Diffuse osteogenic tissue formation was observed by micro-computed tomography with both stem cell types, and the ADSC group displayed similar osteogenesis compared to the BMSC group. In histological assessment, the scaffold pores showed abundant ossification in both groups. Reverse transcription polymerase chain reaction (RT-PCR) showed that the BMSC group had higher expression of genes associated with ossification, and this was confirmed by Western blot analysis. The ADSC- and BMSC-seeded 3D-printed PCL/TCP scaffolds displayed promising enhancement of osteogenesis in a dog model of maxillary bone defects. Full article

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

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17 pages, 5667 KiB

Open AccessReview

Thermal Conductivity of Graphene-Polymer Composites: Mechanisms, Properties, and Applications

by An Li, Cong Zhang and Yang-Fei Zhang^*

Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China

Polymers 2017, 9(9), 437; https://doi.org/10.3390/polym9090437 - 15 Sep 2017

Cited by 371 | Viewed by 40484

Abstract

With the integration and miniaturization of electronic devices, thermal management has become a crucial issue that strongly affects their performance, reliability, and lifetime. One of the current interests in polymer-based composites is thermal conductive composites that dissipate the thermal energy produced by electronic, [...] Read more.

With the integration and miniaturization of electronic devices, thermal management has become a crucial issue that strongly affects their performance, reliability, and lifetime. One of the current interests in polymer-based composites is thermal conductive composites that dissipate the thermal energy produced by electronic, optoelectronic, and photonic devices and systems. Ultrahigh thermal conductivity makes graphene the most promising filler for thermal conductive composites. This article reviews the mechanisms of thermal conduction, the recent advances, and the influencing factors on graphene-polymer composites (GPC). In the end, we also discuss the applications of GPC in thermal engineering. This article summarizes the research on graphene-polymer thermal conductive composites in recent years and provides guidance on the preparation of composites with high thermal conductivity. Full article

(This article belongs to the Special Issue Graphene-Polymer Composites)

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16 pages, 31579 KiB

Open AccessArticle

Effects of Graphene Oxide and Chemically-Reduced Graphene Oxide on the Dynamic Mechanical Properties of Epoxy Amine Composites

by Cristina Monteserín^1,*, Miren Blanco¹, Estibaliz Aranzabe¹, Ana Aranzabe¹, Jose Manuel Laza², Aitor Larrañaga-Varga³ and Jose Luis Vilas²

¹ Unidad de Química de Superficies y Nanotecnología, Fundación Tekniker, Iñaki Goenaga 5, 20600 Eibar, Spain

² Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco/EHU, Apdo. 644, E-48080 Bilbao, Spain

³ SGIker, General Research Services, University of the Basque Country (UPV/EHU), B. Sarriena S/N, 48940 Leioa, Spain

Polymers 2017, 9(9), 449; https://doi.org/10.3390/polym9090449 - 14 Sep 2017

Cited by 79 | Viewed by 13887

Abstract

Composites based on epoxy/graphene oxide (GO) and epoxy/reduced graphene oxide (rGO) were investigated for thermal-mechanical performance focusing on the effects of the chemical groups present on nanoadditive-enhanced surfaces. GO and rGO obtained in the present study have been characterized by Fourier transform infrared [...] Read more.

Composites based on epoxy/graphene oxide (GO) and epoxy/reduced graphene oxide (rGO) were investigated for thermal-mechanical performance focusing on the effects of the chemical groups present on nanoadditive-enhanced surfaces. GO and rGO obtained in the present study have been characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD) demonstrating that materials with different oxidation degrees have been obtained. Thereafter, GO/epoxy and rGO/epoxy nanocomposites were successfully prepared and thoroughly characterized by dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM). A significant increase in the glass transition temperature was found in comparison with the neat epoxy. The presence of functional groups on the graphene surface leads to chemical interactions between these functional groups on GO and rGO surfaces with the epoxy, contributing to the possible formation of covalent bonds between GO and rGO with the matrix. The presence of oxidation groups on GO also contributes to an improved exfoliation, intercalation, and distribution of the GO sheets in the composites with respect to the rGO based composites. Full article

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18 pages, 6035 KiB

Open AccessArticle

How Chain Intermixing Dictates the Polymorphism of PVDF in Poly(vinylidene fluoride)/Polymethylmethacrylate Binary System during Recrystallization: A Comparative Study on Core–Shell Particles and Latex Blend

by Yue Li^1,2, Guoqiang Zhang³

, Shaofeng Song¹

, Haijun Xu¹, Mingwang Pan^1,*

and Gan-Ji Zhong^2,*

¹ Institute of Polymer Science and Engineering, Hebei University of Technology, Tianjin 300130, China

² College of Polymer Science and Engineering, Sichuan University, Chengdu 610065, Sichuan, China

³ Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7202, USA

Polymers 2017, 9(9), 448; https://doi.org/10.3390/polym9090448 - 14 Sep 2017

Cited by 18 | Viewed by 8531

Abstract

In the past few decades, Poly(vinylidene fluoride)/Polymethylmethacrylate (PVDF/PMMA) binary blend has attracted substantial attention in the scientific community due to possible intriguing mechanical, optical and ferroelectric properties that are closely related to its multiple crystal structures/phases. However, the effect of PMMA phase on [...] Read more.

In the past few decades, Poly(vinylidene fluoride)/Polymethylmethacrylate (PVDF/PMMA) binary blend has attracted substantial attention in the scientific community due to possible intriguing mechanical, optical and ferroelectric properties that are closely related to its multiple crystal structures/phases. However, the effect of PMMA phase on the polymorphism of PVDF, especially the relationship between miscibility and polymorphism, remains an open question and is not yet fully understood. In this work, three series of particle blends with varied levels of miscibility between PVDF and PMMA were prepared via seeded emulsion polymerization: PVDF–PMMA core–shell particle (PVDF@PMMA) with high miscibility; PVDF/PMMA latex blend with modest miscibility; and PVDF@c–PMMA (crosslinked PMMA) core–shell particle with negligible miscibility. The difference in miscibility, and the corresponding morphology and polymorphism were systematically studied to correlate the PMMA/PVDF miscibility with PVDF polymorphism. It is of interest to observe that the formation of polar β/γ phase during melt crystallization could be governed in two ways: dipole–dipole interaction and fast crystallization. For PVDF@PMMA and PVDF/PMMA systems, in which fast crystallization was unlikely triggered, higher content of β/γ phase, and intense suppression of crystallization temperature and capacity were observed in PVDF@PMMA, because high miscibility favored a higher intensity of overall dipole–dipole interaction and a longer interaction time. For PVDF@c–PMMA system, after a complete coverage of PVDF seeds by PMMA shells, nearly pure β/γ phase was obtained owing to the fast homogeneous nucleation. This is the first report that high miscibility between PVDF and PMMA could favor the formation of β/γ phase. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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15 pages, 10566 KiB

Open AccessArticle

Imidazolium Ionic Liquid Modified Graphene Oxide: As a Reinforcing Filler and Catalyst in Epoxy Resin

by Qing Lyu¹, Hongxia Yan^1,*, Lin Li¹, Zhengyan Chen¹, Huanhuan Yao¹ and Yufeng Nie²

¹ Department of Applied Chemistry, School of Natural and Applied Sciences, Northwestern Polytechnical University, Xi’an 710129, China

² Department of Applied Mathematics, School of Natural and Applied Sciences, Northwestern Polytechnical University, Xi’an 710129, China

Polymers 2017, 9(9), 447; https://doi.org/10.3390/polym9090447 - 14 Sep 2017

Cited by 49 | Viewed by 10807

Abstract

Surface modification of graphene oxide (GO) is one of the most important issues to produce high performance GO/epoxy composites. In this paper, the imidazole ionic liquid (IMD-Si) was introduced onto the surface of GO sheets by a cheap and simple method, to prepare [...] Read more.

Surface modification of graphene oxide (GO) is one of the most important issues to produce high performance GO/epoxy composites. In this paper, the imidazole ionic liquid (IMD-Si) was introduced onto the surface of GO sheets by a cheap and simple method, to prepare a reinforcing filler, as well as a catalyst in epoxy resin. The interlayer spacing of GO sheets was obviously increased by the intercalation of IMD-Si, which strongly facilitated the dispersibility of graphene oxide in organic solvents and epoxy matrix. The addition of 0.4 wt % imidazolium ionic liquid modified graphene oxide (IMD-Si@GO), yielded a 12% increase in flexural strength (141.3 MPa), a 26% increase in flexural modulus (4.69 GPa), and a 52% increase in impact strength (18.7 kJ/m²), compared to the neat epoxy. Additionally the IMD-Si@GO sheets could catalyze the curing reaction of epoxy resin-anhydride system significantly. Moreover, the improved thermal conductivities and thermal stabilities of epoxy composites filled with IMD-Si@GO were also demonstrated. Full article

(This article belongs to the Special Issue Graphene-Polymer Composites)

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20 pages, 2883 KiB

Open AccessFeature PaperReview

Recent Advances on Polypyrrole Electroactuators

by Bingxi Yan¹, Yu Wu¹ and Liang Guo^1,2,*

¹ Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA

² Department of Neuroscience, The Ohio State University, Columbus, OH 43210, USA

Polymers 2017, 9(9), 446; https://doi.org/10.3390/polym9090446 - 14 Sep 2017

Cited by 50 | Viewed by 9644

Abstract

Featuring controllable electrochemomechanical deformation and excellent biocompatibility, polypyrrole electroactuators used as artificial muscles play a vital role in the design of biomimetic robots and biomedical devices. In the past decade, tremendous efforts have been devoted to their optimization on electroactivity, electrochemical stability, and [...] Read more.

Featuring controllable electrochemomechanical deformation and excellent biocompatibility, polypyrrole electroactuators used as artificial muscles play a vital role in the design of biomimetic robots and biomedical devices. In the past decade, tremendous efforts have been devoted to their optimization on electroactivity, electrochemical stability, and actuation speed, thereby gradually filling the gaps between desired capabilities and practical performances. This review summarizes recent advances on polypyrrole electroactuators, with particular emphases on novel counterions and conformation-reinforcing skeletons. Progress and challenges are comparatively demonstrated and critically analyzed, to enlighten future developments of advanced electroactuators based on polypyrrole and other conducting polymers. Full article

(This article belongs to the Special Issue Electroactive Polymers and Gels)

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16 pages, 9574 KiB

Open AccessReview

Polyphilic Interactions as Structural Driving Force Investigated by Molecular Dynamics Simulation (Project 7)

by Christopher Peschel

, Martin Brehm

and Daniel Sebastiani^*

Institute of Chemistry, Martin-Luther-Universität Halle-Wittenberg, von-Danckelmann-Platz 4, 06120 Halle, Germany

Polymers 2017, 9(9), 445; https://doi.org/10.3390/polym9090445 - 14 Sep 2017

Cited by 2 | Viewed by 5874

Abstract

We investigated the effect of fluorinated molecules on dipalmitoylphosphatidylcholine (DPPC) bilayers by force-field molecular dynamics simulations. In the first step, we developed all-atom force-field parameters for additive molecules in membranes to enable an accurate description of those systems. On the basis of this [...] Read more.

We investigated the effect of fluorinated molecules on dipalmitoylphosphatidylcholine (DPPC) bilayers by force-field molecular dynamics simulations. In the first step, we developed all-atom force-field parameters for additive molecules in membranes to enable an accurate description of those systems. On the basis of this force field, we performed extensive simulations of various bilayer systems containing different additives. The additive molecules were chosen to be of different size and shape, and they included small molecules such as perfluorinated alcohols, but also more complex molecules. From these simulations, we investigated the structural and dynamic effects of the additives on the membrane properties, as well as the behavior of the additive molecules themselves. Our results are in good agreement with other theoretical and experimental studies, and they contribute to a microscopic understanding of interactions, which might be used to specifically tune membrane properties by additives in the future. Full article

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

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16 pages, 7110 KiB

Open AccessFeature PaperArticle

Topological Models for Open-Knotted Protein Chains Using the Concepts of Knotoids and Bonded Knotoids

by Dimos Goundaroulis^1,2

, Neslihan Gügümcü³, Sofia Lambropoulou³, Julien Dorier^1,4

, Andrzej Stasiak^1,2

and Louis Kauffman^5,*

¹ Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland

² SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland

³ Department of Mathematics, National Technical University of Athens, Zografou Campus, 15780 Athens, Greece

⁴ Vital-IT, SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland

⁵ Department of Mathematics, Statistics and Computer Science, University of Illinois at Chicago, Chicago, IL 60607-7045, USA

Polymers 2017, 9(9), 444; https://doi.org/10.3390/polym9090444 - 13 Sep 2017

Cited by 51 | Viewed by 8544

Abstract

In this paper we introduce a method that offers a detailed overview of the entanglement of an open protein chain. Further, we present a purely topological model for classifying open protein chains by also taking into account any bridge involving the backbone. To [...] Read more.

In this paper we introduce a method that offers a detailed overview of the entanglement of an open protein chain. Further, we present a purely topological model for classifying open protein chains by also taking into account any bridge involving the backbone. To this end, we implemented the concepts of planar knotoids and bonded knotoids. We show that the planar knotoids technique provides more refined information regarding the knottedness of a protein when compared to established methods in the literature. Moreover, we demonstrate that our topological model for bonded proteins is robust enough to distinguish all types of lassos in proteins. Full article

(This article belongs to the Special Issue Knotted and Catenated Polymers)

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15 pages, 2167 KiB

Open AccessArticle

Thermoresponsive and Reducible Hyperbranched Polymers Synthesized by RAFT Polymerisation

by Anna Tochwin¹, Alaa El-Betany¹, Hongyun Tai^1,*

, Kai Yu Chan¹, Chester Blackburn¹ and Wenxin Wang²

¹ School of Chemistry, Bangor University, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK

² Charles Institute of Dermatology, University College Dublin, Dublin 4, Ireland

Polymers 2017, 9(9), 443; https://doi.org/10.3390/polym9090443 - 13 Sep 2017

Cited by 14 | Viewed by 9094

Abstract

Here, we report the synthesis of new thermoresponsive hyperbranched polymers (HBPs) via one-pot reversible addition-fragmentation chain transfer (RAFT) copolymerisation of poly(ethylene glycol)methyl ether methacrylate (PEGMEMA, M_n = 475 g/mol), poly(propylene glycol)methacrylate (PPGMA, M_n = 375 g/mol), and disulfide diacrylate (DSDA) using [...] Read more.

Here, we report the synthesis of new thermoresponsive hyperbranched polymers (HBPs) via one-pot reversible addition-fragmentation chain transfer (RAFT) copolymerisation of poly(ethylene glycol)methyl ether methacrylate (PEGMEMA, M_n = 475 g/mol), poly(propylene glycol)methacrylate (PPGMA, M_n = 375 g/mol), and disulfide diacrylate (DSDA) using 2-cyanoprop-2-yl dithiobenzoate as a RAFT agent. DSDA was used as the branching agent and to afford the HBPs with reducible disulfide groups. The resulting HBPs were characterised by Nuclear Magnetic Resonance Spectroscopy (NMR) and Gel Permeation Chromatography (GPC). Differential Scanning Calorimetry (DSC) was used to determine lower critical solution temperatures (LCSTs) of these copolymers, which are in the range of 17–57 °C. Moreover, the studies on the reducibility of HBPs and swelling behaviours of hydrogels synthesized from these HBPs were conducted. The results demonstrated that we have successfully synthesized hyperbranched polymers with desired dual responsive (thermal and reducible) and crosslinkable (via thiol-ene click chemistry) properties. In addition, these new HBPs carry the multiplicity of reactive functionalities, such as RAFT agent moieties and multivinyl functional groups, which can afford them with the capacity for further bioconjugation and structure modifications. Full article

(This article belongs to the Special Issue Living Polymerization)

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13 pages, 3097 KiB

Open AccessCommunication

Multilayered Films Produced by Layer-by-Layer Assembly of Chitosan and Alginate as a Potential Platform for the Formation of Human Adipose-Derived Stem Cell aggregates

by Javad Hatami^1,2,†, Sandra G. Silva^1,2,‡, Mariana B. Oliveira^1,2,†, Rui R. Costa^1,2, Rui L. Reis^1,2 and João F. Mano^1,2,*,†

¹ 3B’s Research Group, Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence of Tissue Engineering and Regenerative Medicine, Avepark—Parque de Ciência e Tecnologia, Zona Industrial da Gandra, 4805-017 Barco GMR, Portugal

² ICVS/3B’s, PT Government Associated Laboratory, Braga/Guimarães, Portugal

^† Current address: Department of Chemistry, CICECO—Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal

^‡ Current address: LAQV/REQUIMTE, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do campo Alegre s/n, 4169-007 Porto, Portugal

Polymers 2017, 9(9), 440; https://doi.org/10.3390/polym9090440 - 13 Sep 2017

Cited by 20 | Viewed by 7052

Abstract

The construction of multilayered films with tunable properties could offer new routes to produce biomaterials as a platform for 3D cell cultivation. In this study, multilayered films produced with five bilayers of chitosan and alginate (CHT/ALG) were built using water-soluble modified mesyl and [...] Read more.

The construction of multilayered films with tunable properties could offer new routes to produce biomaterials as a platform for 3D cell cultivation. In this study, multilayered films produced with five bilayers of chitosan and alginate (CHT/ALG) were built using water-soluble modified mesyl and tosyl–CHT via layer-by-layer (LbL) self-assembly. NMR results demonstrated the presences of mesyl (2.83 ppm) and tosyl groups (2.39, 7.37 and 7.70 ppm) in the chemical structure of modified chitosans. The buildup of multilayered films was monitored by quartz-crystal-microbalance (QCM-D) and film thickness was estimated using the Voigt-based viscoelastic model. QCM-D results demonstrated that CHT/ALG films constructed using mesyl or tosyl modifications (mCHT/ALG) were significantly thinner in comparison to the CHT/ALG films constructed with unmodified chitosan (p < 0.05). Adhesion analysis demonstrated that human adipose stem cells (hASCs) did not adhere to the mCHT/ALG multilayered films and formed aggregates with sizes between ca. 100–200 µm. In vitro studies on cell metabolic activity and live/dead staining suggested that mCHT/ALG multilayered films are nontoxic toward hACSs. Multilayered films produced via LbL assembly of ALG and off-the-shelf, water-soluble modified chitosans could be used as a scaffold for the 3D aggregates formation of hASCs in vitro. Full article

(This article belongs to the Collection Polysaccharides)

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15 pages, 3461 KiB

Open AccessArticle

Influence of the Molar Mass on Long-Chain Branching of Polypropylene

by Florian Kamleitner^1,*, Bernadette Duscher¹, Thomas Koch¹, Simone Knaus², Klaus Schmid³ and Vasiliki-Maria Archodoulaki¹

¹ Institute of Material Science and Technology, TU Wien, Getreidemarkt 9, Vienna 1060, Austria

² Institute of Applied Synthetic Chemistry, TU Wien. Getreidemarkt 9, Vienna 1060, Austria

³ Pergan GmbH, Schlavenhorst 71, Bocholt 46395, Germany

Polymers 2017, 9(9), 442; https://doi.org/10.3390/polym9090442 - 12 Sep 2017

Cited by 20 | Viewed by 8509

Abstract

Long-chain branching (LCB) with peroxydicarbonates (PODIC) is known as a suitable post-reactor process to introduce strain-hardening behaviour and an increase of melt strength to a linear polypropylene (PP). This opens up new possibilities for processing and therefore application. Especially in the case of [...] Read more.

Long-chain branching (LCB) with peroxydicarbonates (PODIC) is known as a suitable post-reactor process to introduce strain-hardening behaviour and an increase of melt strength to a linear polypropylene (PP). This opens up new possibilities for processing and therefore application. Especially in the case of adding value to PP post-consumer waste, LCB is a promising approach. LCB takes place by a combination of chain scission and recombination after radical activation of the PP macromolecule. However, chemical modification of post-consumer waste is challenging because of the inhomogeneous composition and the manifold number of PP grades. The influence of the molar mass of the linear PP precursor on this reaction was studied with different PP grades ranging from extrusion grade to injection moulding grade. To exclude side effects, all PP grades had similar polydispersity indices. A PP with higher molar mass undergoes significant chain scission during the LCB process compared to a PP with low molar mass for injection moulding. Therefore, the two grades differ significantly in their branching number, which influences their behaviour in elongational flow. Full article

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16 pages, 5481 KiB

Open AccessReview

Inkjet Etching of Polymers and Its Applications in Organic Electronic Devices

by Wi Hyoung Lee^1,*

and Yeong Don Park^2,*

¹ Department of Organic and Nano System Engineering, Konkuk University, Seoul 05029, Korea

² Department of Energy and Chemical Engineering, Incheon National University, Incheon 22012, Korea

Polymers 2017, 9(9), 441; https://doi.org/10.3390/polym9090441 - 11 Sep 2017

Cited by 20 | Viewed by 9046

Abstract

Inkjet printing techniques for the etching of polymers and their application to the fabrication of organic electronic devices are reviewed. A mechanism is proposed for the formation of via holes in polymer layers through inkjet printing with solvent, and recent achievements in the [...] Read more.

Inkjet printing techniques for the etching of polymers and their application to the fabrication of organic electronic devices are reviewed. A mechanism is proposed for the formation of via holes in polymer layers through inkjet printing with solvent, and recent achievements in the fabrication with inkjet etching of various three-dimensional microstructures (i.e., microwells, microgrooves, hexagonal holes, and concave structures) are discussed. In addition, organic electronic devices are presented that use inkjet-etched subtractive patterns as platforms for the selective depositions of an emissive material, a liquid crystal, an organic conductor, an organic insulator, and an organic semiconductor, and as an optical waveguide. Full article

(This article belongs to the Special Issue Three-Dimensional Structures: Fabrication and Application)

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14 pages, 4887 KiB

Open AccessArticle

ECG Monitoring Garment Using Conductive Carbon Paste for Reduced Motion Artifacts

by Jin-Woo Lee and Kwang-Seok Yun^*

Department of Electronic Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Korea

Polymers 2017, 9(9), 439; https://doi.org/10.3390/polym9090439 - 11 Sep 2017

Cited by 58 | Viewed by 10208

Abstract

The heart is a fundamental organ of the human circulatory system and the continuous measurement of electrocardiogram (ECG) signals is of great importance for pre-detection of heart diseases. Dry electrodes that do not require electrolyte gel have been developed for wearable ECG monitoring [...] Read more.

The heart is a fundamental organ of the human circulatory system and the continuous measurement of electrocardiogram (ECG) signals is of great importance for pre-detection of heart diseases. Dry electrodes that do not require electrolyte gel have been developed for wearable ECG monitoring applications. However, this kind of electrode often introduces motion artifacts because of the high contact impedance between the electrode and skin. We propose a wearable ECG monitoring garment that employs electrodes made of conductive carbon-based paste. This paste is directly applied to the skin and after drying for 5 min, it forms a patch electrode that is detachable and flexible. The contact impedance between the patch electrode and the skin is very low because the paste covers the skin in a conformal manner. The experimental results show that the contact area of the carbon-based paste on the skin replica is almost 100%. At frequencies under 10 Hz, the contact impedance of the patch electrode is of 70.0 kΩ, much lower than the typical 118.7 kΩ impedance of a Ag/AgCl electrode. We also demonstrate that the ECG signals measured using the custom-designed garment and the patch electrodes are very stable even during actions such as walking and running. Full article

(This article belongs to the Special Issue Wearable Sensor)

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20 pages, 5814 KiB

Open AccessArticle

Finite Element Modeling for Debonding of FRP-to-Concrete Interfaces Subjected to Mixed-Mode Loading

by Hui Yu¹, Yu-Lei Bai^1,*, Jian-Guo Dai²

and Wan-Yang Gao³

¹ Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100022, China

² Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong 999077, China

³ School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Polymers 2017, 9(9), 438; https://doi.org/10.3390/polym9090438 - 9 Sep 2017

Cited by 33 | Viewed by 8524

Abstract

This paper presents finite element (FE) modeling of the debonding behavior of fiber reinforced polymer (FRP)-to-concrete interfaces subject to mixed-mode loading, which is realized through a peeling test of FRP composites externally bonded onto a concrete substrate. A cohesive zone model (CZM) is [...] Read more.

This paper presents finite element (FE) modeling of the debonding behavior of fiber reinforced polymer (FRP)-to-concrete interfaces subject to mixed-mode loading, which is realized through a peeling test of FRP composites externally bonded onto a concrete substrate. A cohesive zone model (CZM) is implemented into the FE model to represent the behavior of the FRP-to-concrete interface. Two element schemes (orthotropic plane stress element and beam element) were employed to simulate the behavior of FRP composite plate in the peeling test. The orthotropic plane stress element scheme, bearing a clear physical background and with an easy definition of the material property parameters following the composite mechanics, is found to be superior to the beam element scheme, and thus is utilized to conduct parametric studies. The influences of the peeling angle, the interfacial parameters (i.e., the configuration of the cohesive zone models, the interfacial damage initiation law (DIL), the interfacial damage evolution law (DEL), the coupling of mode-I and mode-II components), on the mixed-mode failure of the FRP-concrete-interface are carefully investigated. The results showed that the mode I component plays a critical role in the debonding failure of FRP-to-concrete interfaces even when the peeling angle is very small. The failure of FRP-to-concrete interface transits promptly from a mode II-dominated one to a mode I-dominated one when the peeling angle increases to a relatively small value (e.g., 4 degree) and subsequently the peeling force (i.e., the debonding strength of FRP) decreases dramatically. Such mixity of the mode I and mode II components should be appropriately considered for refining the analysis of FRP-strengthened RC beams and the FRP debonding strength design, for which a pure mode II interfacial failure was usually assumed. Full article

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9 pages, 1490 KiB

Open AccessArticle

Detection of Black Plastics in the Middle Infrared Spectrum (MIR) Using Photon Up-Conversion Technique for Polymer Recycling Purposes

by Wolfgang Becker^*

, Kerstin Sachsenheimer and Melanie Klemenz

Fraunhofer Institut fuer Chemische Technologie (ICT), P.O. Box 12 40, 76327 Pfinztal, Germany

Polymers 2017, 9(9), 435; https://doi.org/10.3390/polym9090435 - 8 Sep 2017

Cited by 69 | Viewed by 13685

Abstract

The identification of black polymers which contain about 0.5 to 3 mass percent soot or black master batch is still an essential problem in recycling sorting processes. Near infrared spectroscopy (NIRS) of non-black polymers offers a reliable and fast identification, and is therefore [...] Read more.

The identification of black polymers which contain about 0.5 to 3 mass percent soot or black master batch is still an essential problem in recycling sorting processes. Near infrared spectroscopy (NIRS) of non-black polymers offers a reliable and fast identification, and is therefore suitable for industrial application. NIRS is consequently widely used in polymer sorting plants. However, this method cannot be used for black polymers because small amounts of carbon black or soot absorb all light in the NIR spectral region. Spectroscopy in the mid infrared spectral region (MIR) offers a possibility to identify black polymers. MIR spectral measurements carried out with Fourier-transform infrared spectrometers (FTIR) are not fast enough to meet economic requirements in sorting plants. By contrast, spectrometer systems based on the photon up-conversion technique are fast and sensitive enough and can be applied to sort black polymer parts. Such a system is able to measure several thousand spectra per second hence is suitable for industrial applications. The results of spectral measurements of black polymers are presented. Full article

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14 pages, 5760 KiB

Open AccessArticle

Helix Electrohydrodynamic Printing of Highly Aligned Serpentine Micro/Nanofibers

by Yongqing Duan^1,2, Yajiang Ding^1,2, Zhoulong Xu^1,2, YongAn Huang^1,2,* and Zhouping Yin^1,2,*

¹ State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China

² Flexible Electronics Research Center, Huazhong University of Science and Technology, Wuhan 430074, China

Polymers 2017, 9(9), 434; https://doi.org/10.3390/polym9090434 - 8 Sep 2017

Cited by 41 | Viewed by 8074

Abstract

Micro/nano serpentine structures have widespread applications in flexible/stretchable electronics; however, challenges still exist for low-cost, high-efficiency and controllable manufacturing. Helix electrohydrodynamic printing (HE-printing) has been proposed here to realize controllable direct-writing of large area, highly aligned serpentine micro/nanofibers by introducing the rope coiling [...] Read more.

Micro/nano serpentine structures have widespread applications in flexible/stretchable electronics; however, challenges still exist for low-cost, high-efficiency and controllable manufacturing. Helix electrohydrodynamic printing (HE-printing) has been proposed here to realize controllable direct-writing of large area, highly aligned serpentine micro/nanofibers by introducing the rope coiling effect into printing process. By manipulating the flying trajectory and solidification degree of the micro/nano jet, the solidified micro/nanofiber flying in a stabilized helical manner and versatile serpentine structures deposited on a moving collector have been achieved. Systematic experiments and theoretical analysis were conducted to study the transformation behavior and the size changing rules for various deposited microstructures, and highly aligned serpentine microfibers were directly written by controlling the applied voltage, nozzle-to-collector distance and collector velocity. Furthermore, a hyper-stretchable piezoelectric device that can detect stretching, bending and pressure has been successfully fabricated using the printed serpentine micro/nanofibers, demonstrating the potential of HE-printing in stretchable electronics manufacturing. Full article

(This article belongs to the Special Issue Electrospinning of Nanofibres)

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24 pages, 8573 KiB

Open AccessReview

Poly(phenylene ether) Based Amphiphilic Block Copolymers

by Edward N. Peters

SABIC, Selkirk, NY 12158, USA

Polymers 2017, 9(9), 433; https://doi.org/10.3390/polym9090433 - 8 Sep 2017

Cited by 14 | Viewed by 10802

Abstract

Polyphenylene ether (PPE) telechelic macromonomers are unique hydrophobic polyols which have been used to prepare amphiphilic block copolymers. Various polymer compositions have been synthesized with hydrophilic blocks. Their macromolecular nature affords a range of structures including random, alternating, and di- and triblock copolymers. [...] Read more.

Polyphenylene ether (PPE) telechelic macromonomers are unique hydrophobic polyols which have been used to prepare amphiphilic block copolymers. Various polymer compositions have been synthesized with hydrophilic blocks. Their macromolecular nature affords a range of structures including random, alternating, and di- and triblock copolymers. New macromolecular architectures can offer tailored property profiles for optimum performance. Besides reducing moisture uptake and making the polymer surface more hydrophobic, the PPE hydrophobic segment has good compatibility with polystyrene (polystyrene-philic). In general, the PPE contributes to the toughness, strength, and thermal performance. Hydrophilic segments go beyond their affinity for water. Improvements in the interfacial adhesion between polymers and polar substrates via hydrogen bonding and good compatibility with polyesters (polyester-philic) have been exhibited. The heterogeneity of domains in these PPE based block copolymer offers important contributions to diverse applications. Full article

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

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16 pages, 3666 KiB

Open AccessArticle

Effect of Graphene Oxide on the Reaction Kinetics of Methyl Methacrylate In Situ Radical Polymerization via the Bulk or Solution Technique

by Ioannis S. Tsagkalias, Triantafyllos K. Manios and Dimitris S. Achilias^*

Laboratory of Polymer Chemistry and Technology, Department of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece

Polymers 2017, 9(9), 432; https://doi.org/10.3390/polym9090432 - 8 Sep 2017

Cited by 35 | Viewed by 8135

Abstract

The synthesis of nanocomposite materials based on poly(methyl methacrylate) and graphene oxide (GO) is presented using the in situ polymerization technique, starting from methyl methacrylate, graphite oxide, and an initiator, and carried out either with (solution) or without (bulk) in the presence of [...] Read more.

The synthesis of nanocomposite materials based on poly(methyl methacrylate) and graphene oxide (GO) is presented using the in situ polymerization technique, starting from methyl methacrylate, graphite oxide, and an initiator, and carried out either with (solution) or without (bulk) in the presence of a suitable solvent. Reaction kinetics was followed gravimetrically and the appropriate characterization of the products took place using several experimental techniques. X-ray diffraction (XRD) data showed that graphite oxide had been transformed to graphene oxide during polymerization, whereas FTIR spectra revealed no significant interactions between the polymer matrix and GO. It appears that during polymerization, the initiator efficiency was reduced by the presence of GO, resulting in a reduction of the reaction rate and a slight increase in the average molecular weight of the polymer formed, measured by gel permeation chromatography (GPC), along with an increase in the glass transition temperature obtained from differential scanning calorimetry (DSC). The presence of the solvent results in the suppression of the gel-effect in the reaction rate curves, the synthesis of polymers with lower average molecular weights and polydispersities of the Molecular Weight Distribution, and lower glass transition temperatures. Finally, from thermogravimetric analysis (TG), it was verified that the presence of GO slightly enhances the thermal stability of the nano-hybrids formed. Full article

(This article belongs to the Special Issue Graphene-Polymer Composites)

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