Polymers

12 pages, 4333 KiB

Open AccessArticle

Electrospinning Pullulan Fibers from Salt Solutions

by Ran Li^1,2, Peggy Tomasula¹

, Ana Margarida Moreira De Sousa¹, Shih-Chuan Liu^1,3,*, Michael Tunick¹, Kevin Liu⁴ and Linshu Liu^1,*

¹ Dairy and Functional Foods Research Unit, Eastern Regional Research Center, Agricultural Research Service, US Department of Agriculture, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA

² State Key Laboratory of Separation Membranes and Membrane Processes, Tianjin Polytechnic University, #399 Binshuixi Road, Xiqing District, Tianjin 300387, China

³ School of Health Diet and Industry Management, Chung-Shan Medical University and Department of Nutrition, Chung Shan Medical University Hospital, No. 110, Sec. 1, Jianguo N. Rd., South District, Taichung 402, Taiwan

⁴ National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 N. University Street, Peoria, IL 61604, USA

Polymers 2017, 9(1), 32; https://doi.org/10.3390/polym9010032 - 22 Jan 2017

Cited by 32 | Viewed by 8660

Abstract

There is an increasing interest in applying the technology of electrospinning for making ultrafine fibers from biopolymers for food-grade applications, and using pullulan (PUL) as a carrier to improve the electrospinnability of proteins and other naturally occurring polyelectrolytes. In this study, PUL solutions [...] Read more.

There is an increasing interest in applying the technology of electrospinning for making ultrafine fibers from biopolymers for food-grade applications, and using pullulan (PUL) as a carrier to improve the electrospinnability of proteins and other naturally occurring polyelectrolytes. In this study, PUL solutions containing NaCl or Na₃C₆H₅O₇ at different concentrations were electrospun. The inclusion of salts interrupted the hydrogen bonding and altered solution properties, such as viscosity, electric conductivity, and surface tension, as well as physical properties of fibers thus obtained, such as appearance, size, and melting point. The exogenous Na⁺ associated to the oxygen in the C6 position of PUL as suggested by FTIR measurement and was maintained during electrospinning. Bead-free PUL fibers could be electrospun from PUL solution (8%, w/v) in the presence of a 0.20 M NaCl (124 ± 34 nm) or 0.05 M Na₃C₆H₅O₇ (154 ± 36 nm). The further increase of NaCl or Na₃C₆H₅O₇ resulted in fibers that were flat with larger diameter sizes and defects. SEM also showed excess salt adhering on the surfaces of PUL fibers. Since most food processing is not carried out in pure water, information obtained through the present research is useful for the development of electrospinning biopolymers for food-grade applications. Full article

▼ Show Figures

Graphical abstract

17 pages, 4917 KiB

Open AccessArticle

A Comprehensive Systematic Study on Thermoresponsive Gels: Beyond the Common Architectures of Linear Terpolymers

by Anna P. Constantinou, Hanyi Zhao, Catriona M. McGilvery

, Alexandra E. Porter and Theoni K. Georgiou^*

Department of Materials, Imperial College London, Royal School of Mines, Exhibition Road, London SW7 2AZ, UK

Polymers 2017, 9(1), 31; https://doi.org/10.3390/polym9010031 - 20 Jan 2017

Cited by 29 | Viewed by 9672

Abstract

In this study, seven thermoresponsive methacrylate terpolymers with the same molar mass (MM) and composition but various architectures were successfully synthesized using group transfer polymerization (GTP). These terpolymers were based on tri(ethylene glycol) methyl ether methacrylate (TEGMA, A unit), n-butyl methacrylate (BuMA, [...] Read more.

In this study, seven thermoresponsive methacrylate terpolymers with the same molar mass (MM) and composition but various architectures were successfully synthesized using group transfer polymerization (GTP). These terpolymers were based on tri(ethylene glycol) methyl ether methacrylate (TEGMA, A unit), n-butyl methacrylate (BuMA, B unit), and 2-(dimethylamino)ethyl methacrylate (DMAEMA, C unit). Along with the more common ABC, ACB, BAC, and statistical architectures, three diblock terpolymers were also synthesized and investigated for the first time, namely (AB)C, A(BC), and B(AC); where the units in the brackets are randomly copolymerized. Two BC diblock copolymers were also synthesized for comparison. Their hydrodynamic diameters and their effective pK_as were determined by dynamic light scattering (DLS) and hydrogen ion titrations, respectively. The self-assembly behavior of the copolymers was also visualized by transmission electron microscopy (TEM). Both dilute and concentrated aqueous copolymer solutions were extensively studied by visual tests and their cloud points (CP) and gel points were determined. It is proven that the aqueous solution properties of the copolymers, with specific interest in their thermoresponsive properties, are influenced by the architecture, with the ABC and A(BC) ones to show clear sol-gel transition. Full article

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

▼ Show Figures

Graphical abstract

15 pages, 2391 KiB

Open AccessArticle

Structural Features and the Anti-Inflammatory Effect of Green Tea Extract-Loaded Liquid Crystalline Systems Intended for Skin Delivery

by Patricia Bento da Silva^*,†, Giovana Maria Fioramonti Calixto^†

, João Augusto Oshiro Júnior^†

, Raisa Lana Ávila Bombardelli, Bruno Fonseca-Santos

, Camila Fernanda Rodero and Marlus Chorilli^*

¹ School of Pharmaceutical Sciences, São Paulo State University—UNESP, Rodovia Araraquara-Jaú, km. 1, Campus, 14801-903 Araraquara, São Paulo, Brazil

^† These authors contributed equally to this work.

Polymers 2017, 9(1), 30; https://doi.org/10.3390/polym9010030 - 18 Jan 2017

Cited by 23 | Viewed by 6633

Abstract

Camellia sinensis, which is obtained from green tea extract (GTE), has been widely used in therapy owing to the antioxidant, chemoprotective, and anti-inflammatory activities of its chemical components. However, GTE is an unstable compound, and may undergo reactions that lead to a [...] Read more.

Camellia sinensis, which is obtained from green tea extract (GTE), has been widely used in therapy owing to the antioxidant, chemoprotective, and anti-inflammatory activities of its chemical components. However, GTE is an unstable compound, and may undergo reactions that lead to a reduction or loss of its effectiveness and even its degradation. Hence, an attractive approach to overcome this problem to protect the GTE is its incorporation into liquid crystalline systems (LCS) that are drug delivery nanostructured systems with different rheological properties, since LCS have both fluid liquid and crystalline solid properties. Therefore, the aim of this study was to develop and characterize GTE-loaded LCS composed of polyoxypropylene (5) polyoxyethylene (20) cetyl alcohol, avocado oil, and water (F25E, F29E, and F32E) with different rheological properties and to determine their anti-inflammatory efficacy. Polarized light microscopy revealed that the formulations F25, F29, and F32 showed hexagonal, cubic, and lamellar liquid crystalline mesophases, respectively. Rheological studies showed that F32 is a viscous Newtonian liquid, while F25 and F29 are dilatant and pseudoplastic non-Newtonian fluids, respectively. All GTE-loaded LCS behaved as pseudoplastic with thixotropy; furthermore, the presence of GTE increased the S values and decreased the n values, especially in F29, indicating that this LCS has the most organized structure. Mechanical and bioadhesive properties of GTE-unloaded and -loaded LCS corroborated the rheological data, showing that F29 had the highest mechanical and bioadhesive values. Finally, in vivo inflammation assay revealed that the less elastic and consistent LCS, F25E and F32E presented statistically the same anti-inflammatory activity compared to the positive control, decreasing significantly the paw edema after 4 h; whereas, the most structured and elastic LCS, F29E, strongly limited the potential effects of GTE. Thereby, the development of drug delivery systems with suitable rheological properties may enhance GTE bioavailability, enabling its administration via the skin for the treatment of inflammation. Full article

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

▼ Show Figures

Graphical abstract

10 pages, 2032 KiB

Open AccessArticle

A Green Platform for Preparation of the Well-Defined Polyacrylonitrile: ⁶⁰Co γ-ray Irradiation-Initiated RAFT Polymerization at Room Temperature

by Shuangshuang Zhang¹, Lu Yin¹, Junzhi Wang^1,2, Wei Zhang^1,*

, Lifen Zhang¹

and Xiulin Zhu^1,*

¹ Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China

² Faculty of Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada

Polymers 2017, 9(1), 26; https://doi.org/10.3390/polym9010026 - 17 Jan 2017

Cited by 13 | Viewed by 6626

Abstract

⁶⁰Co γ-ray irradiation-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization at room temperature with 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the chain transfer agent was first applied to acrylonitrile (AN) polymerization, providing a “green” platform for preparing polyacrylonitrile (PAN)-based carbon fibers using an environment-friendly energy [...] Read more.

⁶⁰Co γ-ray irradiation-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization at room temperature with 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the chain transfer agent was first applied to acrylonitrile (AN) polymerization, providing a “green” platform for preparing polyacrylonitrile (PAN)-based carbon fibers using an environment-friendly energy source. Various effects of dose rate, molar ratio of the monomer to the chain transfer agent, monomer concentration and reaction time on the AN polymerization behaviors were performed to improve the controllability of molecular the weight and molecular weight distribution of the obtained PAN. The feature of the controlled polymerization was proven by the first-order kinetics, linear increase of the molecular weight with the monomer conversion and a successful chain-extension experiment. The molecular weight and molecular weight distribution of PAN were characterized by size exclusion chromatography (SEC). ¹H NMR and Matrix assisted laser desorption ionization/time of flight mass spectra (MALDI-TOF-MS) confirmed the chain-end functionality of PAN, which also was supported by the successful chain-extension experiments of original PANs with acrylonitrile and styrene as the second monomers respectively. Full article

▼ Show Figures

Figure 1

15 pages, 4504 KiB

Open AccessArticle

Multi-Objective Optimizations of Biodegradable Polymer Stent Structure and Stent Microinjection Molding Process

by Hongxia Li^1,*, Xinyu Wang¹, Yunbo Wei¹

, Tao Liu¹, Junfeng Gu², Zheng Li², Minjie Wang¹, Danyang Zhao¹, Aike Qiao³ and Yahua Liu¹

¹ School of Mechanical Engineering, Dalian University of Technology, Dalian 116023, China

² Department of Engineering Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116023, China

³ College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, China

Polymers 2017, 9(1), 20; https://doi.org/10.3390/polym9010020 - 17 Jan 2017

Cited by 30 | Viewed by 8167

Abstract

Biodegradable stents made of poly-l-lactic acid (PLLA) have a promising prospect thanks to high biocompatibility and a favorable biodegradation period. However, due to the low stiffness of PLLA, polymeric stents have a lower radial stiffness and larger foreshortening. Furthermore, a stent [...] Read more.

Biodegradable stents made of poly-l-lactic acid (PLLA) have a promising prospect thanks to high biocompatibility and a favorable biodegradation period. However, due to the low stiffness of PLLA, polymeric stents have a lower radial stiffness and larger foreshortening. Furthermore, a stent is a tiny meshed tube, hence, it is difficult to make a polymeric stent. In the present study, a finite element analysis-based optimization method combined with Kriging surrogate modeling is firstly proposed to optimize the stent structure and stent microinjection molding process, so as to improve the stent mechanical properties and microinjection molding quality, respectively. The Kriging surrogate models are constructed to formulate the approximate mathematical relationships between the design variables and design objectives. Expected improvement is employed to balance local and global search to find the global optimal design. As an example, the polymeric ART18Z stent was investigated. The mechanical properties of stent expansion in a stenotic artery and the molding quality were improved after optimization. Numerical results demonstrate the proposed optimization method can be used for the computationally measurable optimality of stent structure design and stent microinjection molding process. Full article

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

▼ Show Figures

Figure 1

28 pages, 8221 KiB

Open AccessReview

Recent Advances in Conjugated Polymer-Based Microwave Absorbing Materials

by Ying Wang

, Yunchen Du^*

, Ping Xu, Rong Qiang and Xijiang Han^*

MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China

Polymers 2017, 9(1), 29; https://doi.org/10.3390/polym9010029 - 14 Jan 2017

Cited by 131 | Viewed by 13917

Abstract

Microwave absorbing materials (MAMs) are paving the way for exciting applications in electromagnetic (EM) pollution precaution and national defense security, as they offer an advanced alternative to conventional reflection principles to fundamentally eliminate the EM waves. Conjugated polymer (CP)-based composites appear as a [...] Read more.

Microwave absorbing materials (MAMs) are paving the way for exciting applications in electromagnetic (EM) pollution precaution and national defense security, as they offer an advanced alternative to conventional reflection principles to fundamentally eliminate the EM waves. Conjugated polymer (CP)-based composites appear as a promising kind of MAM with the desirable features of low density and high performance. In this review, we introduce the theory of microwave absorption and summarize recent advances in the fabrication of CP-based MAMs, including rational design of the microstructure of pure conjugated polymers and tunable chemical integration with magnetic ferrites, magnetic metals, transition metal oxides, and carbon materials. The key point of enhancing microwave absorption in CP-based MAMs is to regulate their EM properties, improve matching of characteristic impedance, and create diversified loss mechanisms. The examples presented in this review will provide new insights into the design and preparation of CP-based composites that can satisfy the high demands of the oncoming generation of MAMs. Full article

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

▼ Show Figures

Figure 1

18 pages, 4964 KiB

Open AccessArticle

Effect of Short-Term Water Exposure on the Mechanical Properties of Halloysite Nanotube-Multi Layer Graphene Reinforced Polyester Nanocomposites

by Mohd Shahneel Saharudin^1,2,*, Rasheed Atif²

and Fawad Inam²

¹ Institute of Product Design and Manufacturing (UniKL IPROM), Universiti Kuala Lumpur, 56100 Cheras, Kuala Lumpur, Malaysia

² Department of Mechanical and Construction Engineering, Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne NE1 8ST, UK

Polymers 2017, 9(1), 27; https://doi.org/10.3390/polym9010027 - 14 Jan 2017

Cited by 17 | Viewed by 8200

Abstract

The influence of short-term water absorption on the mechanical properties of halloysite nanotubes-multi layer graphene reinforced polyester hybrid nanocomposites has been investigated. The addition of nano-fillers significantly increased the flexural strength, tensile strength, and impact strength in dry and wet conditions. After short-term [...] Read more.

The influence of short-term water absorption on the mechanical properties of halloysite nanotubes-multi layer graphene reinforced polyester hybrid nanocomposites has been investigated. The addition of nano-fillers significantly increased the flexural strength, tensile strength, and impact strength in dry and wet conditions. After short-term water exposure, the maximum microhardness, tensile, flexural and impact toughness values were observed at 0.1 wt % multi-layer graphene (MLG). The microhardness increased up to 50.3%, tensile strength increased up to 40% and flexural strength increased up to 44%. Compared to dry samples, the fracture toughness and surface roughness of all types of produced nanocomposites were increased that may be attributed to the plasticization effect. Scanning electron microscopy revealed that the main failure mechanism is caused by the weakening of the nano-filler-matrix interface induced by water absorption. It was further observed that synergistic effects were not effective at a concentration of 0.1 wt % to produce considerable improvement in the mechanical properties of the produced hybrid nanocomposites. Full article

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

▼ Show Figures

Figure 1

12 pages, 2674 KiB

Open AccessArticle

Flexible Transparent Electrode of Hybrid Ag-Nanowire/Reduced-Graphene-Oxide Thin Film on PET Substrate Prepared Using H2/Ar Low-Damage Plasma

by Chi-Hsien Huang^1,*

, Yin-Yin Wang¹, Tsung-Han Lu¹ and Yen-Cheng Li²

¹ Department of Materials Engineering, Ming Chi University of Technology, 84 Gungjuan Rd., Taishan Dist., New Taipei City 243, Taiwan

² Material and Chemical Research Laboratories, Industrial Technology Research Institute, 195, Sec. 4, Chung Hsin Rd., Chutung, Hsinchu 300, Taiwan

Polymers 2017, 9(1), 28; https://doi.org/10.3390/polym9010028 - 13 Jan 2017

Cited by 9 | Viewed by 7949

Abstract

We employ H₂/Ar low-damage plasma treatment (H₂/Ar-LDPT) to reduce graphene oxide (GO) coating on a polymer substrate—polyethylene terephthalate (PET)—with the assistance of atomic hydrogen (H_α) at low temperature of 70 °C. Four-point probing and ultraviolet-visible (UV-Vis) spectroscopy [...] Read more.

We employ H₂/Ar low-damage plasma treatment (H₂/Ar-LDPT) to reduce graphene oxide (GO) coating on a polymer substrate—polyethylene terephthalate (PET)—with the assistance of atomic hydrogen (H_α) at low temperature of 70 °C. Four-point probing and ultraviolet-visible (UV-Vis) spectroscopy demonstrate that the conductivity and transmittance can be controlled by varying the H₂/Ar flow rate, treatment time, and radio-frequency (RF) power. Optical emission spectroscopy reveals that the H_α intensity depends on these processing parameters, which influence the removal of oxidative functional groups (confirmed via X-ray photoelectron spectroscopy) to yield reduced GO (rGO). To further improve the conductivity while maintaining high transmittance, we introduce silver nanowires (AgNWs) between rGO and a PET substrate to obtain a hybrid rGO/AgNWs/PET with a sheet resistance of ~100 Ω/sq and 81% transmittance. In addition, the hybrid rGO/AgNWs thin film also shows high flexibility and durability and is suitable for flexible and wearable electronics applications. Full article

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

▼ Show Figures

Graphical abstract

16 pages, 8028 KiB

Open AccessArticle

Nitrogen Doped Macroporous Carbon as Electrode Materials for High Capacity of Supercapacitor

by Yudong Li¹, Xianzhu Xu¹, Yanzhen He², Yanqiu Jiang^1,* and Kaifeng Lin^1,*

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

² School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China

Polymers 2017, 9(1), 2; https://doi.org/10.3390/polym9010002 - 13 Jan 2017

Cited by 32 | Viewed by 9065

Abstract

Nitrogen doped carbon materials as electrodes of supercapacitors have attracted abundant attention. Herein, we demonstrated a method to synthesize N-doped macroporous carbon materials (NMC) with continuous channels and large size pores carbonized from polyaniline using multiporous silica beads as sacrificial templates to act [...] Read more.

Nitrogen doped carbon materials as electrodes of supercapacitors have attracted abundant attention. Herein, we demonstrated a method to synthesize N-doped macroporous carbon materials (NMC) with continuous channels and large size pores carbonized from polyaniline using multiporous silica beads as sacrificial templates to act as electrode materials in supercapacitors. By the nice carbonized process, i.e., pre-carbonization at 400 °C and then pyrolysis at 700/800/900/1000 °C, NMC replicas with high BET specific surface areas exhibit excellent stability and recyclability as well as superb capacitance behavior (~413 F

\cdot

g⁻¹) in alkaline electrolyte. This research may provide a method to synthesize macroporous materials with continuous channels and hierarchical pores to enhance the infiltration and mass transfer not only used as electrode, but also as catalyst somewhere micro- or mesopores do not work well. Full article

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

▼ Show Figures

Figure 1

16 pages, 5154 KiB

Open AccessReview

Development of Conjugated Polymers for Memory Device Applications

by Hung-Ju Yen^1,*

, Changsheng Shan¹

, Leeyih Wang², Ping Xu³, Ming Zhou⁴ and Hsing-Lin Wang^1,*

¹ Physical Chemistry and Applied Spectroscopy (C-PCS), Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA

² Center for Condensed Matter Science, National Taiwan University, 1 Roosevelt Road, 4th Sec., Taipei 10617, Taiwan

³ School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China

⁴ Department of Chemistry, Northeast Normal University, Changchun 130024, China

Polymers 2017, 9(1), 25; https://doi.org/10.3390/polym9010025 - 12 Jan 2017

Cited by 38 | Viewed by 11805

Abstract

This review summarizes the most widely used mechanisms in memory devices based on conjugated polymers, such as charge transfer, space charge traps, and filament conduction. In addition, recent studies of conjugated polymers for memory device applications are also reviewed, discussed, and differentiated based [...] Read more.

This review summarizes the most widely used mechanisms in memory devices based on conjugated polymers, such as charge transfer, space charge traps, and filament conduction. In addition, recent studies of conjugated polymers for memory device applications are also reviewed, discussed, and differentiated based on the mechanisms and structural design. Moreover, the electrical conditions of conjugated polymers can be further fine-tuned by careful design and synthesis based on the switching mechanisms. The review also emphasizes and demonstrates the structure-memory properties relationship of donor-acceptor conjugated polymers for advanced memory device applications. Full article

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

▼ Show Figures

Graphical abstract

12 pages, 25893 KiB

Open AccessArticle

Molecular Dynamics Simulations for Resolving Scaling Laws of Polyethylene Melts

by Kazuaki Z. Takahashi^1,2,*, Ryuto Nishimura², Kenji Yasuoka² and Yuichi Masubuchi³

¹ Multi-Scale Soft-Matter Simulation Team, Research Center for Computational Design of Advanced Functional Materials, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan

² Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan

³ National Composite Center, Nagoya University, Furocho, Chikusa, Nagoya 464-8630, Japan

Polymers 2017, 9(1), 24; https://doi.org/10.3390/polym9010024 - 12 Jan 2017

Cited by 26 | Viewed by 8587

Abstract

Long-timescale molecular dynamics simulations were performed to estimate the actual physical nature of a united-atom model of polyethylene (PE). Several scaling laws for representative polymer properties are compared to theoretical predictions. Internal structure results indicate a clear departure from theoretical predictions that assume [...] Read more.

Long-timescale molecular dynamics simulations were performed to estimate the actual physical nature of a united-atom model of polyethylene (PE). Several scaling laws for representative polymer properties are compared to theoretical predictions. Internal structure results indicate a clear departure from theoretical predictions that assume ideal chain statics. Chain motion deviates from predictions that assume ideal motion of short chains. With regard to linear viscoelasticity, the presence or absence of entanglements strongly affects the duration of the theoretical behavior. Overall, the results indicate that Gaussian statics and dynamics are not necessarily established for real atomistic models of PE. Moreover, the actual physical nature should be carefully considered when using atomistic models for applications that expect typical polymer behaviors. Full article

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

▼ Show Figures

Figure 1

11 pages, 201 KiB

Open AccessEditorial

Acknowledgement to Reviewers of Polymers in 2016

by Polymers Editorial Office

MDPI AG, St. Alban-Anlage 66, 4052 Basel, Switzerland

Polymers 2017, 9(1), 23; https://doi.org/10.3390/polym9010023 - 10 Jan 2017

Cited by 7 | Viewed by 5985

Abstract

The editors of Polymers would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2016.[...] Full article

18 pages, 3097 KiB

Open AccessArticle

Investigation of Thermal and Thermomechanical Properties of Biodegradable PLA/PBSA Composites Processed via Supercritical Fluid-Assisted Foam Injection Molding

by Sai Aditya Pradeep^1,2, Hrishikesh Kharbas³, Lih-Sheng Turng³, Abraham Avalos⁴, Joseph G. Lawrence⁴ and Srikanth Pilla^1,2,*

¹ Department of Automotive Engineering, Clemson University, Clemson, SC 29607, USA

² Department of Material Science and Engineering, Clemson University, Clemson, SC 29634, USA

³ Polymer Engineering Center, Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA

⁴ Polymer Institute, University of Toledo, Toledo, OH 43606, USA

Polymers 2017, 9(1), 22; https://doi.org/10.3390/polym9010022 - 9 Jan 2017

Cited by 48 | Viewed by 11560

Abstract

Bio-based polymer foams have been gaining immense attention in recent years due to their positive contribution towards reducing the global carbon footprint, lightweighting, and enhancing sustainability. Currently, polylactic acid (PLA) remains the most abundant commercially consumed biopolymer, but suffers from major drawbacks such [...] Read more.

Bio-based polymer foams have been gaining immense attention in recent years due to their positive contribution towards reducing the global carbon footprint, lightweighting, and enhancing sustainability. Currently, polylactic acid (PLA) remains the most abundant commercially consumed biopolymer, but suffers from major drawbacks such as slow crystallization rate and poor melt processability. However, blending of PLA with a secondary polymer would enhance the crystallization rate and the thermal properties based on their compatibility. This study investigates the physical and compatibilized blends of PLA/poly (butylene succinate-co-adipate) (PBSA) processed via supercritical fluid-assisted (ScF) injection molding technology using nitrogen (N₂) as a facile physical blowing agent. Furthermore, this study aims at understanding the effect of blending and ScF foaming of PLA/PBSA on crystallinity, melting, and viscoelastic behavior. Results show that compatibilization, upon addition of triphenyl phosphite (TPP), led to an increase in molecular weight and a shift in melting temperature. Additionally, the glass transition temperature (T_g) obtained from the tanδ curve was observed to be in agreement with the T_g value predicted by the Gordon–Taylor equation, further confirming the compatibility of PLA and PBSA. The compatibilization of ScF-foamed PLA–PBSA was found to have an increased crystallinity and storage modulus compared to their physically foamed counterparts. Full article

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

▼ Show Figures

Graphical abstract

24 pages, 1003 KiB

Open AccessReview

Chitosan Combined with ZnO, TiO₂ and Ag Nanoparticles for Antimicrobial Wound Healing Applications: A Mini Review of the Research Trends

by Vu Khac Hoang Bui¹, Duckshin Park² and Young-Chul Lee^1,*

¹ Department of BioNano Technology, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si 13120, Gyeonggi-do, Korea

² Korea Railroad Research Institute (KRRI), 176 Cheoldobakmulkwan-ro, Uiwang-si 16105, Gyeonggi-do, Korea

Polymers 2017, 9(1), 21; https://doi.org/10.3390/polym9010021 - 9 Jan 2017

Cited by 220 | Viewed by 20346

Abstract

Chitosan is a natural polymer that has been widely utilized for many purposes in the food, textile, agriculture, water treatment, cosmetic and pharmaceutical industries. Based on its characteristics, including biodegradability, non-toxicity and antimicrobial properties, it has been employed effectively in wound healing applications. [...] Read more.

Chitosan is a natural polymer that has been widely utilized for many purposes in the food, textile, agriculture, water treatment, cosmetic and pharmaceutical industries. Based on its characteristics, including biodegradability, non-toxicity and antimicrobial properties, it has been employed effectively in wound healing applications. Importantly, however, it is necessary to improve chitosan’s capacities by combination with zinc oxide (ZnO), titanium dioxide (TiO₂) and silver (Ag) nanoparticles (NPs). In this review of many of the latest research papers, we take a closer look at the antibacterial effectiveness of chitosan combined with ZnO, TiO₂ and Ag NPs and also evaluate the specific wound healing application potentials. Full article

(This article belongs to the Collection Polysaccharides)

▼ Show Figures

Graphical abstract

80 pages, 7798 KiB

Open AccessReview

A Review of Multiscale Computational Methods in Polymeric Materials

by Ali Gooneie^*

, Stephan Schuschnigg

and Clemens Holzer

Chair of Polymer Processing, Montanuniversitaet Leoben, Otto Gloeckel-Strasse 2, 8700 Leoben, Austria

Polymers 2017, 9(1), 16; https://doi.org/10.3390/polym9010016 - 9 Jan 2017

Cited by 171 | Viewed by 19101

Abstract

Polymeric materials display distinguished characteristics which stem from the interplay of phenomena at various length and time scales. Further development of polymer systems critically relies on a comprehensive understanding of the fundamentals of their hierarchical structure and behaviors. As such, the inherent multiscale [...] Read more.

Polymeric materials display distinguished characteristics which stem from the interplay of phenomena at various length and time scales. Further development of polymer systems critically relies on a comprehensive understanding of the fundamentals of their hierarchical structure and behaviors. As such, the inherent multiscale nature of polymer systems is only reflected by a multiscale analysis which accounts for all important mechanisms. Since multiscale modelling is a rapidly growing multidisciplinary field, the emerging possibilities and challenges can be of a truly diverse nature. The present review attempts to provide a rather comprehensive overview of the recent developments in the field of multiscale modelling and simulation of polymeric materials. In order to understand the characteristics of the building blocks of multiscale methods, first a brief review of some significant computational methods at individual length and time scales is provided. These methods cover quantum mechanical scale, atomistic domain (Monte Carlo and molecular dynamics), mesoscopic scale (Brownian dynamics, dissipative particle dynamics, and lattice Boltzmann method), and finally macroscopic realm (finite element and volume methods). Afterwards, different prescriptions to envelope these methods in a multiscale strategy are discussed in details. Sequential, concurrent, and adaptive resolution schemes are presented along with the latest updates and ongoing challenges in research. In sequential methods, various systematic coarse-graining and backmapping approaches are addressed. For the concurrent strategy, we aimed to introduce the fundamentals and significant methods including the handshaking concept, energy-based, and force-based coupling approaches. Although such methods are very popular in metals and carbon nanomaterials, their use in polymeric materials is still limited. We have illustrated their applications in polymer science by several examples hoping for raising attention towards the existing possibilities. The relatively new adaptive resolution schemes are then covered including their advantages and shortcomings. Finally, some novel ideas in order to extend the reaches of atomistic techniques are reviewed. We conclude the review by outlining the existing challenges and possibilities for future research. Full article

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

▼ Show Figures

Graphical abstract

9 pages, 4224 KiB

Open AccessArticle

Crystal Crosslinked Gels with Aggregation-Induced Emissive Crosslinker Exhibiting Swelling Degree-Dependent Photoluminescence

by Tsuyoshi Oura¹, Ryosuke Taniguchi¹, Kenta Kokado^1,2,*

and Kazuki Sada^2,*

¹ Graduate School of Chemical Sciences and Engineering, Hokkaido University, Kita10 Nishi8, Kita-ku, Sapporo 060-0810, Japan

² Department of Chemistry, Faculty of Science, Hokkaido University, Kita10 Nishi8, Kita-ku, Sapporo 060-0810, Japan

Polymers 2017, 9(1), 19; https://doi.org/10.3390/polym9010019 - 6 Jan 2017

Cited by 21 | Viewed by 7881

Abstract

The synthesis and photoluminescence properties of crystal crosslinked gels (CCGs) with an aggregation-induced emission (AIE) active crosslinker derived from tetraphenylethene (TPE) is discussed in this article. The CCG was prepared from a metal organic framework (MOF) with large pore aperture to allow the [...] Read more.

The synthesis and photoluminescence properties of crystal crosslinked gels (CCGs) with an aggregation-induced emission (AIE) active crosslinker derived from tetraphenylethene (TPE) is discussed in this article. The CCG was prepared from a metal organic framework (MOF) with large pore aperture to allow the penetration of TPE crosslinker. The obtained CCG possessed a rectangular shape originated from the parent MOF, KUMOF. The CCG showed stimuli-responsive photoluminescence behavior depending on the swelling degree, thus the photoluminescence intensity was higher at higher swelling degree. By changing the solvent, water content, or ionic strength, the photoluminescence intensity was controllable, accompanying the change of swelling degree. Moreover, emission color tuning was also achieved by the introduction of luminescent rare earth ions to form a coordination bonding with residual carboxylate inside the CCG. Full article

(This article belongs to the Special Issue Selected Papers from the Symposium “Polymer Gels as Advanced Soft Materials” at PacifiChem2015)

▼ Show Figures

Graphical abstract

13 pages, 1366 KiB

Open AccessArticle

Investigation of the Influence of PLA Molecular Structure on the Crystalline Forms (α’ and α) and Mechanical Properties of Wet Spinning Fibres

by Michał Puchalski^*

, Sylwia Kwolek, Grzegorz Szparaga, Michał Chrzanowski and Izabella Krucińska

Department of Material and Commodity Sciences and Textile Metrology, Faculty of Material Technologies and Textile Design, Centre of Advanced Technologies of Human-Friendly Textiles “Pro Humano Tex”, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland

Polymers 2017, 9(1), 18; https://doi.org/10.3390/polym9010018 - 6 Jan 2017

Cited by 80 | Viewed by 10456

Abstract

In this paper, the influence of the molecular structure of polylactide (PLA)—characterised by its molar mass and content of d-lactide isomer—on the molecular ordering and α’–α form transition during fibre manufacturing by the wet spinning method is described. Fibres were studied by [...] Read more.

In this paper, the influence of the molecular structure of polylactide (PLA)—characterised by its molar mass and content of d-lactide isomer—on the molecular ordering and α’–α form transition during fibre manufacturing by the wet spinning method is described. Fibres were studied by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Additionally, the physical and mechanical properties of the fibres were determined. This study also examines the preliminary molecular ordering and crystallisation of PLA fibres at various draw ratios. The performed experiments clearly show the dependence of the molecular ordering of PLA on the molar mass and d-lactide content during the wet spinning process. The fibres manufactured from PLA with the lowest content of d-lactide and the lowest molar mass were characterised by a higher tendency for crystallisation and a higher possibility to undergo the disorder-to-order phase transition (α’ to α form). The structural changes in PLA explain the observed changes in the physical and mechanical properties of the obtained fibres. Full article

▼ Show Figures

Figure 1

22 pages, 3962 KiB

Open AccessArticle

Electrodeposition of Mn-Co/Polypyrrole Nanocomposites: An Electrochemical and In Situ Soft-X-ray Microspectroscopic Investigation

by Benedetto Bozzini^1,*

, Patrizia Bocchetta¹

, George Kourousias² and Alessandra Gianoncelli²

¹ Dipartimento di Ingegneria dell’Innovazione, Università del Salento, via Monteroni, 73100 Lecce, Italy

² Elettra-Sincrotrone Trieste S.C.p.A. strada statale 14 km 163.5 in Area Science Park, Basovizza, 34012 Trieste, Italy

Polymers 2017, 9(1), 17; https://doi.org/10.3390/polym9010017 - 6 Jan 2017

Cited by 20 | Viewed by 7287

Abstract

Understanding the lateral variations in the elemental and chemical state of constituents induced by electrochemical reactions at nanoscales is crucial for the advancement of electrochemical materials science. This requires in situ studies to provide observables that contribute to both modeling beyond the phenomenological [...] Read more.

Understanding the lateral variations in the elemental and chemical state of constituents induced by electrochemical reactions at nanoscales is crucial for the advancement of electrochemical materials science. This requires in situ studies to provide observables that contribute to both modeling beyond the phenomenological level and exactly transducing the functionally relevant quantities. A range of X-ray coherent diffraction imaging (CDI) approaches have recently been proposed for imaging beyond the diffraction limit with potentially dramatic improvements in time resolution with chemical sensitivity. In this paper, we report a selection of ptychography results obtained in situ during the electrodeposition of a metal–polymer nanocomposite. Our selection includes dynamic imaging during electrochemically driven growth complemented with absorption and phase spectroscopy with high lateral resolution. We demonstrate the onset of morphological instability feature formation and correlate the chemical state of Mn with the local growth rate controlled by the current density distribution resulting from morphological evolution. Full article

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

▼ Show Figures

Figure 1

11 pages, 1580 KiB

Open AccessArticle

Preparation and Properties of Branched Polystyrene through Radical Suspension Polymerization

by Wenyan Huang, Weikai Gu, Hongjun Yang, Xiaoqiang Xue, Bibiao Jiang^*, Dongliang Zhang, Jianbo Fang, Jianhai Chen, Yang Yang and Jinlong Guo

School of Materials Science and Engineering, Changzhou University, Changzhou 213164, China

Polymers 2017, 9(1), 14; https://doi.org/10.3390/polym9010014 - 6 Jan 2017

Cited by 14 | Viewed by 9065

Abstract

Radical solvent-free suspension polymerization of styrene with 3-mercapto hexyl-methacrylate (MHM) as the branching monomer has been carried out using 2,2′-azobisisobutyronitrile (AIBN) as the initiator to prepare branched polymer beads of high purity. The molecular weight and branching structure of the polymers have been [...] Read more.

Radical solvent-free suspension polymerization of styrene with 3-mercapto hexyl-methacrylate (MHM) as the branching monomer has been carried out using 2,2′-azobisisobutyronitrile (AIBN) as the initiator to prepare branched polymer beads of high purity. The molecular weight and branching structure of the polymers have been characterized by triple detection size exclusion chromatography (TD-SEC), proton nuclear magnetic resonance spectroscopy (¹H-NMR), and Fourier transform infrared spectroscopy (FTIR). The glass transition temperature and rheological properties have been measured by using differential scanning calorimetry (DSC) and rotational rheometry. At mole ratios of MHM to AIBN less than 1.0, gelation was successfully avoided and branched polystyrene beads were prepared in the absence of any solvent. Branched polystyrene has a relatively higher molecular weight and narrower polydispersity (M_w.MALLS = 1,036,000 g·mol⁻¹, M_w/M_n = 7.76) than those obtained in solution polymerization. Compared with their linear analogues, lower glass transition temperature and decreased chain entanglement were observed in the presently obtained branched polystyrene because of the effects of branching. Full article

▼ Show Figures

Figure 1

19 pages, 1109 KiB

Open AccessArticle

Polymer Conformations in Ionic Microgels in the Presence of Salt: Theoretical and Mesoscale Simulation Results

by Hideki Kobayashi¹, Rene Halver², Godehard Sutmann² and Roland G. Winkler^1,*

¹ Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich, Germany

² Jülich Supercomputing Centre, Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany

Polymers 2017, 9(1), 15; https://doi.org/10.3390/polym9010015 - 5 Jan 2017

Cited by 44 | Viewed by 7071

Abstract

We investigate the conformational properties of polymers in ionic microgels in the presence of salt ions by molecular dynamics simulations and analytical theory. A microgel particle consists of coarse-grained linear polymers, which are tetra-functionally crosslinked. Counterions and salt ions are taken into account [...] Read more.

We investigate the conformational properties of polymers in ionic microgels in the presence of salt ions by molecular dynamics simulations and analytical theory. A microgel particle consists of coarse-grained linear polymers, which are tetra-functionally crosslinked. Counterions and salt ions are taken into account explicitly, and charge-charge interactions are described by the Coulomb potential. By varying the charge interaction strength and salt concentration, we characterize the swelling of the polyelectrolytes and the charge distribution. In particular, we determine the amount of trapped mobile charges inside the microgel and the Debye screening length. Moreover, we analyze the polymer extension theoretically in terms of the tension blob model taking into account counterions and salt ions implicitly by the Debye–Hückel model. Our studies reveal a strong dependence of the amount of ions absorbed in the interior of the microgel on the electrostatic interaction strength, which is related to the degree of the gel swelling. This implies a dependence of the inverse Debye screening length κ on the ion concentration; we find a power-law increase of κ with the Coulomb interaction strength with the exponent

3 / 5

for a salt-free microgel and an exponent

1 / 2

for moderate salt concentrations. Additionally, the radial dependence of polymer conformations and ion distributions is addressed. Full article

(This article belongs to the Collection Polyelectrolytes)

▼ Show Figures

Graphical abstract

26 pages, 2145 KiB

Open AccessReview

Applications of Functionalized Carbon Nanotubes for the Therapy and Diagnosis of Cancer

by Yongsung Hwang^1,2, Sung-Hoon Park^3,* and Jin Woo Lee^4,*

¹ Soonchunhyang Institute of Medi-bio Science, Soonchunhyang University, Cheonan-si, Chungcheongnam-do 31151, Korea

² Institute of Tissue Regeneration, College of Medicine, Soonchunhyang University, Cheonan-si, Chungcheongnam-do 31151, Korea

³ Department of Mechanical Engineering, Soongsil University, Dongjak-gu, Seoul 06978, Korea

⁴ Department of Molecular Medicine, School of Medicine, Gachon University, Incheon 21999, Korea

Polymers 2017, 9(1), 13; https://doi.org/10.3390/polym9010013 - 4 Jan 2017

Cited by 72 | Viewed by 12118

Abstract

Carbon nanotubes (CNTs) are attractive nanostructures that serve as multifunctional transporters in biomedical applications, especially in the field of cancer therapy and diagnosis. Owing to their easily tunable nature and remarkable properties, numerous functionalizations and treatments of CNTs have been attempted for their [...] Read more.

Carbon nanotubes (CNTs) are attractive nanostructures that serve as multifunctional transporters in biomedical applications, especially in the field of cancer therapy and diagnosis. Owing to their easily tunable nature and remarkable properties, numerous functionalizations and treatments of CNTs have been attempted for their utilization as hybrid nano-carriers in the delivery of various anticancer drugs, genes, proteins, and immunotherapeutic molecules. In this review, we discuss the current advances in the applications of CNT-based novel delivery systems with an emphasis on the various functionalizations of CNTs. We also highlight recent findings that demonstrate their important roles in cancer imaging applications, demonstrating their potential as unique agents with high-level ultrasonic emission, strong Raman scattering resonance, and magnetic properties. Full article

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

▼ Show Figures

Figure 1

12 pages, 5287 KiB

Open AccessArticle

Electrical, Mechanical, and Thermal Properties of LDPE Graphene Nanoplatelets Composites Produced by Means of Melt Extrusion Process

by Karolina Gaska^*, Xiangdong Xu, Stanislaw Gubanski and Roland Kádár

Department of Materials and Manufacturing Technology, Chalmers University of Technology, SE 412-96 Gothenburg, Sweden

Polymers 2017, 9(1), 11; https://doi.org/10.3390/polym9010011 - 4 Jan 2017

Cited by 105 | Viewed by 13347

Abstract

Composites of LDPE filled with different amounts of graphene nanoplatelets (GnP) were prepared in form of films by means of precoating technique and single screw melt-extrusion using two types of screws, compression and mixing. This manufacturing process imposes strong anisotropy on the sample’s [...] Read more.

Composites of LDPE filled with different amounts of graphene nanoplatelets (GnP) were prepared in form of films by means of precoating technique and single screw melt-extrusion using two types of screws, compression and mixing. This manufacturing process imposes strong anisotropy on the sample’s morphology, in which the nanoplatelets become oriented along the extrusion direction. Such orientation of GnP in LDPE matrix is confirmed by scanning electron microscopy observations and it yields unique electrical properties. As compared to pure LDPE, significant reductions of the through-plane conductivity are found for the composites at relatively low electric fields (<20 kV/mm) at low filler concentrations. Above the field level of 20 kV/mm, a crossover effect is observed that results in a strong field dependency of the conductivity where the non-linear behavior starts to dominate. Moreover, differential scanning calorimetry (DSC) results indicate a decrease in polymer crystallinity of the composite matrix with increasing filler content, whereas thermogravimetric (TG) analysis shows a slight increase in the material’s thermal stability. Application of GnP also leads to improvement of mechanical properties, manifested by the increase of Young’s modulus and tensile strength in both types of samples. Full article

▼ Show Figures

Graphical abstract

11 pages, 3231 KiB

Open AccessCommunication

Pentynyl Ether of β-Cyclodextrin Polymer and Silica Micro-Particles: A New Hybrid Material for Adsorption of Phenanthrene from Water

by Jae Min Choi¹, Daham Jeong², Eunae Cho¹, Jae-Hyuk Yu³

, Muhammad Nazir Tahir^4,* and Seunho Jung^1,2,*

¹ Center for Biotechnology Research in UBITA (CBRU), Institute for Ubiquitous Information Technology and Applications (UBITA), Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea

² Department of Systems Biotechnology, Microbial Carbohydrate Resource Bank (MCRB) & Center for Biotechnology Research in UBITA (CBRU), Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea

³ Department of Bacteriology, The University of Wisconsin-Madison, Madison, WI 53706, USA

⁴ Nanoqam, Department of Chemistry, University of Quebec at Montreal, P.O. Box 8888, Succ. Centre-ville, Montreal, QC H3C 3P8, Canada

Polymers 2017, 9(1), 10; https://doi.org/10.3390/polym9010010 - 4 Jan 2017

Cited by 13 | Viewed by 10234

Abstract

A new hybrid material for the removal of polycyclic aromatic hydrocarbons (PAH) from water was prepared by the polymerization of pentynyl beta-cyclodextrin (PyβCD) and silica micro-particles (SMP). Phenanthrene, being one of the important members of the PAH family and a potential risk for [...] Read more.

A new hybrid material for the removal of polycyclic aromatic hydrocarbons (PAH) from water was prepared by the polymerization of pentynyl beta-cyclodextrin (PyβCD) and silica micro-particles (SMP). Phenanthrene, being one of the important members of the PAH family and a potential risk for environmental pollution, was selected for this study. Results show that phenanthrene removal efficiency of the SMP was improved significantly after hybridization with PyβCD-polymer. Approximately 50% of the phenanthrene was removed in the first 60 min and more than 95% was removed in less than 7 h when 25 mL of the 2 ppm aqueous phenanthrene solution was incubated with the 100 mg of SMP-PyβCD-polymer material. Infrared spectroscopy and thermal gravimetric analysis show that the enhanced efficiency of the SMP-PyβCD-polymer compared to the unmodified SMP was due to the formation of the inclusion complexation of phenanthrene with the PyβCD. These results indicate that SMP-PyβCD polymers have a potential to be applied as molecular filters in water purification systems and also for waste water treatment. Full article

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

▼ Show Figures

Graphical abstract

13 pages, 14370 KiB

Open AccessArticle

Preparation and Characterization of Highly Aligned Carbon Nanotubes/Polyacrylonitrile Composite Nanofibers

by Yanhua Song, Zhaoyang Sun, Lan Xu^*

and Zhongbiao Shao

National Engineering Laboratory for Modern Silk, College of Textile and Engineering, Soochow University, 199 Ren-ai Road, Suzhou 215123, China

Polymers 2017, 9(1), 1; https://doi.org/10.3390/polym9010001 - 3 Jan 2017

Cited by 163 | Viewed by 10078

Abstract

In the electrospinning process, a modified parallel electrode method (MPEM), conducted by placing a positively charged ring between the needle and the parallel electrode collector, was used to fabricate highly aligned carbon nanotubes/polyacrylonitrile (CNTs/PAN) composite nanofibers. Characterizations of the samples—such as morphology, the [...] Read more.

In the electrospinning process, a modified parallel electrode method (MPEM), conducted by placing a positively charged ring between the needle and the parallel electrode collector, was used to fabricate highly aligned carbon nanotubes/polyacrylonitrile (CNTs/PAN) composite nanofibers. Characterizations of the samples—such as morphology, the degree of alignment, and mechanical and conductive properties—were investigated by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), universal testing machine, high-resistance meter, and other methods. The results showed the MPEM could improve the alignment and uniformity of electrospun CNTs/PAN composite nanofibers, and enhance their mechanical and conductive properties. This meant the successful preparation of highly aligned CNT-reinforced PAN nanofibers with enhanced physical properties, suggesting their potential application in appliances and communication areas. Full article

▼ Show Figures

Graphical abstract

15 pages, 8234 KiB

Open AccessArticle

The Influence of Biochemical Modification on the Properties of Adhesive Compounds

by Anna Rudawska^1,*

, Izabela Haniecka¹, Magdalena Jaszek² and Monika Osińska-Jaroszuk²

¹ Faculty of Mechanical Engineering, Lublin University of Technology, 20-618 Lublin, Poland

² Department of Biochemistry, Maria Sklodowska-Curie University, 20-033 Lublin, Poland

Polymers 2017, 9(1), 9; https://doi.org/10.3390/polym9010009 - 31 Dec 2016

Cited by 7 | Viewed by 5671

Abstract

The main objective of this study was to determine the effect of biochemical modification of epoxy adhesive compounds on the mechanical properties of a cured adhesive exposed to various climatic factors. The epoxy adhesive was modified by lyophilized fungal metabolites and prepared by [...] Read more.

The main objective of this study was to determine the effect of biochemical modification of epoxy adhesive compounds on the mechanical properties of a cured adhesive exposed to various climatic factors. The epoxy adhesive was modified by lyophilized fungal metabolites and prepared by three methods. Additionally, the adhesive compound specimens were seasoned for two months at a temperature of 50 °C and 50% humidity in a climate test chamber, Espec SH 661. The tensile strength tests of the adhesive compounds were performed using a Zwick/Roell Z150 testing machine in compliance with the DIN EN ISO 527-1 standard. The examination of the adhesive specimens was performed using two microscopes: a LEO 912AB transmission electron microscope equipped with Quantax 200 for EDS X-ray spectroscopy and a Zeiss 510 META confocal microscope coupled to an AxioVert 200M. The experiments involved the use of a CT Skyscan 1172 tomograph. The results revealed that some mechanical properties of the modified adhesives were significantly affected by both the method of preparation of the adhesive compound and the content of the modifying agent. In addition, it was found that seasoning of the modified adhesives does not lead to a decrease in some of their mechanical properties. Full article

(This article belongs to the Special Issue Renewable Polymeric Adhesives)

▼ Show Figures

Figure 1

19 pages, 4124 KiB

Open AccessReview

Light-Responsive Polymer Micro- and Nano-Capsules

by Valentina Marturano^1,2, Pierfrancesco Cerruti^2,*

, Marta Giamberini³

, Bartosz Tylkowski⁴ and Veronica Ambrogi¹

¹ Department of Chemical, Materials and Production Engineering (DICMAPI), University of Naples “Federico II”, P. le Tecchio, 80, 80125 Napoli, Italy

² Institute for Polymers, Composites and Biomaterials (IPCB-CNR), Via Campi Flegrei, 34, 80078 Pozzuoli (NA), Italy

³ Department of Chemical Engineering (DEQ), Universitat Rovira i Virgili, Av. Països Catalans, 26, 43007 Tarragona, Spain

⁴ Chemistry Technology Centre of Catalonia (CTQC), C/Marcel·lí Domingo, 43007 Tarragona, Spain

Polymers 2017, 9(1), 8; https://doi.org/10.3390/polym9010008 - 29 Dec 2016

Cited by 86 | Viewed by 18846

Abstract

A significant amount of academic and industrial research efforts are devoted to the encapsulation of active substances within micro- or nanocarriers. The ultimate goal of core–shell systems is the protection of the encapsulated substance from the environment, and its controlled and targeted release. [...] Read more.

A significant amount of academic and industrial research efforts are devoted to the encapsulation of active substances within micro- or nanocarriers. The ultimate goal of core–shell systems is the protection of the encapsulated substance from the environment, and its controlled and targeted release. This can be accomplished by employing “stimuli-responsive” materials as constituents of the capsule shell. Among a wide range of factors that induce the release of the core material, we focus herein on the light stimulus. In polymers, this feature can be achieved introducing a photo-sensitive segment, whose activation leads to either rupture or modification of the diffusive properties of the capsule shell, allowing the delivery of the encapsulated material. Micro- and nano-encapsulation techniques are constantly spreading towards wider application fields, and many different active molecules have been encapsulated, such as additives for food-packaging, pesticides, dyes, pharmaceutics, fragrances and flavors or cosmetics. Herein, a review on the latest and most challenging polymer-based micro- and nano-sized hollow carriers exhibiting a light-responsive release behavior is presented. A special focus is put on systems activated by wavelengths less harmful for living organisms (mainly in the ultraviolet, visible and infrared range), as well as on different preparation techniques, namely liposomes, self-assembly, layer-by-layer, and interfacial polymerization. Full article

(This article belongs to the Special Issue Responsive Polymers for Drug Delivery, Imaging and Theranostic Functions)

▼ Show Figures

Graphical abstract

17 pages, 4840 KiB

Open AccessArticle

Characterization of Thermoplastic Polyurethane (TPU) and Ag-Carbon Black TPU Nanocomposite for Potential Application in Additive Manufacturing

by Steven T. Patton^1,*, Chenggang Chen¹, Jianjun Hu¹, Lawrence Grazulis¹, Amanda M. Schrand² and Ajit K. Roy³

¹ Nonstructural Materials Division, University of Dayton Research Institute, Dayton, OH 45469-0050, USA

² Munitions Directorate, Air Force Research Laboratory, Eglin Air Force Base, Valparaiso, FL 45433-7750, USA

³ Materials & Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, OH 45433-7750, USA

Polymers 2017, 9(1), 6; https://doi.org/10.3390/polym9010006 - 29 Dec 2016

Cited by 38 | Viewed by 13847

Abstract

Electromechanical, adhesion, and viscoelastic properties of polymers and polymer nanocomposites (PNCs) are of interest for additive manufacturing (AM) and flexible electronics. Development/optimization of inks for AM is complex, expensive, and substrate/interface dependent. This study investigates properties of free standing films of a thermoplastic [...] Read more.

Electromechanical, adhesion, and viscoelastic properties of polymers and polymer nanocomposites (PNCs) are of interest for additive manufacturing (AM) and flexible electronics. Development/optimization of inks for AM is complex, expensive, and substrate/interface dependent. This study investigates properties of free standing films of a thermoplastic polyurethane (TPU) polymer and an Ag–carbon black (Ag-CB) TPU PNC in a lightly loaded low strain compression contact as a rough measure of their suitability for AM. The TPU exhibited high hysteresis and a large viscoelastic response, and sufficient dwell time was needed for polymer chain relaxation and measurable adhesion. A new discovery is that large enough contact area is needed to allow longer time constant polymer ordering in the contact that led to higher adhesion and better performance/reliability. This has previously unknown implications for interface size relative to polymer chain length in AM design. The standard linear model was found to be a good fit for the viscoelastic behavior of the TPU. The PNC exhibited no adhesion (new result), low electrical resistance, and relatively small viscoelastic response. This implies potential for AM electrical trace as well as switch applications. Full article

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

▼ Show Figures

Figure 1

14 pages, 2416 KiB

Open AccessArticle

Gamma-Irradiation Effects on the Spectral and Amplified Spontaneous Emission (ASE) Properties of Conjugated Polymers in Solution

by Mohamad S. AlSalhi^1,2,*

, Saradh Prasad^1,2,3

, D. Devaraj³ and Ziad S. Abo Mustafa¹

¹ Department of Physics and Astronomy, College of Science, King Saud University, Riyadh 11451, Saudi Arabia

² Research Chair on Laser Diagnosis of Cancers, College of Science, King Saud University, Riyadh 11451, Saudi Arabia

³ Department of Electrical and Electronics, College of Engineering, Kalasalingam University, Anad Nagar, Krishnankoil, Virudhunagar 626190, Tamil Nadu, India

Polymers 2017, 9(1), 7; https://doi.org/10.3390/polym9010007 - 28 Dec 2016

Cited by 4 | Viewed by 5926

Abstract

In this paper, we investigate the effects of gamma (γ) radiation on the spectral and mplified spontaneous emission (ASE) properties of two conjugated polymers (CPs) viz., poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH–PPV) (CPM) and poly{[2-[2′,5′-bis(2″-ethylhexyloxy)phenyl]-1,4-phenylenevinylene]-co-[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene]} (BEHP-co-MEH–PPV) (BMP) in tetrahydrofuran [...] Read more.

In this paper, we investigate the effects of gamma (γ) radiation on the spectral and mplified spontaneous emission (ASE) properties of two conjugated polymers (CPs) viz., poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH–PPV) (CPM) and poly{[2-[2′,5′-bis(2″-ethylhexyloxy)phenyl]-1,4-phenylenevinylene]-co-[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene]} (BEHP-co-MEH–PPV) (BMP) in tetrahydrofuran (THF). Gamma irradiation strongly affected the photophysical properties of these CPs. To explore these changes, gamma radiation, in the range of 2–50 kGy, was used to maintain the temperature at 5 °C constant for all doses at a dose rate of 12.67 kGy/h, using a ⁶⁰Co gamma ray. The ASE profiles of the CPs in THF were obtained under the high power excitation of a Nd:YAG laser (355 nm), pre- and post-radiation. The result revealed a dramatic blue shift of the fluorescence and the ASE spectra after gamma irradiation. This shift in the luminescence and ASE spectra could be a response to the conformational disorders such as gamma irradiation-induced polymer crosslinking, which was verified using Raman spectra, FTIR, and swelling experiments. This could be the first report on the effect of gamma radiation on the ASE properties of conjugated polymers. Full article

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

▼ Show Figures

Graphical abstract

14 pages, 3660 KiB

Open AccessArticle

Rapid and Effective Removal of Cu²⁺ from Aqueous Solution Using Novel Chitosan and Laponite-Based Nanocomposite as Adsorbent

by Jie Cao^1,*, Han Cao¹, Yuejun Zhu^2,3, Shanshan Wang^2,3, Dingwei Qian¹, Guodong Chen¹, Mingbo Sun^1,* and Weian Huang¹

¹ School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China

² State Key Laboratory of Offshore Oil Exploitation, Beijing 100027, China

³ CNOOC Research Institute, Beijing 100027, China

Polymers 2017, 9(1), 5; https://doi.org/10.3390/polym9010005 - 27 Dec 2016

Cited by 28 | Viewed by 7323

Abstract

In this paper, a novel method for preparing nanoparticle-polymer hybrid adsorbent was established. Laponite was dispersed in distilled water to form Laponite nanoparticles. These nanoparticles were pre-adsorbed by 2-acrylamido-2-methylpropane-sulfonic acid (AMPS) to improve their dispersion stability in chitosan solution. The nanoparticle-polymer hybrid adsorbent [...] Read more.

In this paper, a novel method for preparing nanoparticle-polymer hybrid adsorbent was established. Laponite was dispersed in distilled water to form Laponite nanoparticles. These nanoparticles were pre-adsorbed by 2-acrylamido-2-methylpropane-sulfonic acid (AMPS) to improve their dispersion stability in chitosan solution. The nanoparticle-polymer hybrid adsorbent was prepared by copolymerization of chitosan, acrylamide, acrylic acid, AMPS, and Laponite nanoparticles. Four adsorbents were obtained and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller adsorption (BET). Additionally, the uptake capacities of Cu²⁺ using different samples were studied. Compared to the adsorbent without chitosan and Laponite components, the maximum uptake of the hybrid adsorbent increased from 0.58 to 1.28 mmol·g⁻¹ and the adsorption equilibrium time of it decreased from more than 75 min to less than 35 min, which indicated that the addition of chitosan and Laponite could greatly increase the adsorption rate and capacity of polymer adsorbent. The effects of different experimental parameters—such as initial pH, temperature, and equilibrium Cu²⁺ concentration—on the adsorption capacities were studied. Desorption study indicated that this hybrid adsorbent was easy to be regenerated. Full article

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

▼ Show Figures

Graphical abstract

8 pages, 723 KiB

Open AccessArticle

Reversible Addition-Fragmentation Chain Transfer Polymerization of Acrylonitrile under Irradiation of Blue LED Light

by Zhicheng Huang, Lifen Zhang^*

, Zhenping Cheng^* and Xiulin Zhu

Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Department of Polymer Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China

Polymers 2017, 9(1), 4; https://doi.org/10.3390/polym9010004 - 26 Dec 2016

Cited by 19 | Viewed by 6781

Abstract

Compared to unhealthy UV or γ-ray and high-energy-consumption thermal external stimuli, the promising light emitting diode (LED) external stimulus has some outstanding technological merits such as narrow wavelength distribution, low heat generation and energy consumption, and safety for human beings. In this work, [...] Read more.

Compared to unhealthy UV or γ-ray and high-energy-consumption thermal external stimuli, the promising light emitting diode (LED) external stimulus has some outstanding technological merits such as narrow wavelength distribution, low heat generation and energy consumption, and safety for human beings. In this work, a novel reversible addition-fragmentation transfer (RAFT) polymerization system for acrylonitrile (AN) was developed under the irradiation of blue LED light at room temperature, using 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a novel radical initiator and 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) as the typical chain transfer agent. Well-defined polyacrylonitrile (PAN) with a controlled molecular weight and narrow molecular weight distribution was successfully synthesized. This strategy may provide another effective method for scientific researchers or the industrial community to synthesize a PAN-based precursor of carbon fibers. Full article

▼ Show Figures

Graphical abstract

Journal Menu

Journal Browser

Polymers, Volume 9, Issue 1 (January 2017) – 30 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI