Polymers

441 KiB

Open AccessArticle

Polyamide 6/Multiwalled Carbon Nanotubes Nanocomposites with Modified Morphology and Thermal Properties

by Nasir Mahmood, Mohammad Islam, Asad Hameed and Shaukat Saeed

Polymers 2013, 5(4), 1380-1391; https://doi.org/10.3390/polym5041380 - 5 Dec 2013

Cited by 86 | Viewed by 12206

Pure polyamide 6 (PA6) and polyamide 6/carbon nanotube (PA6/CNT) composite samples with 0.5 weight percent loading of pristine or functionalized CNTs were made using a solution mixing technique. Modification of nanotube surface as a result of chemical functionalization was confirmed through the presence [...] Read more.

Pure polyamide 6 (PA6) and polyamide 6/carbon nanotube (PA6/CNT) composite samples with 0.5 weight percent loading of pristine or functionalized CNTs were made using a solution mixing technique. Modification of nanotube surface as a result of chemical functionalization was confirmed through the presence of lattice defects as examined under high-resolution transmission electron microscope and absorption bands characteristic of carboxylic, sulfonic and amine chemical groups. Microstructural examination of the cryogenically fractured surfaces revealed qualitative information regarding CNT dispersion within PA6 matrix and interfacial strength. X-ray diffraction studies indicated formation of thermodynamically more stable α-phase crystals. Thermogravimetric analysis revealed that CNT incorporation delayed onset of thermal degradation by as much as 70 °C in case of amine-functionalized CNTs, thus increasing thermal stability of the composites. Furthermore, addition of amine-functionalized CNTs caused an increase in crystallization and melting temperatures from the respective values of 177 and 213 °C (for neat PA6) to 211 and 230 °C (for composite), respectively. Full article

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891 KiB

Open AccessArticle

Synthesis and Gas Transport Properties of Hyperbranched Polyimide–Silica Hybrid/Composite Membranes

by Masako Miki, Hideki Horiuchi and Yasuharu Yamada

Polymers 2013, 5(4), 1362-1379; https://doi.org/10.3390/polym5041362 - 4 Dec 2013

Cited by 18 | Viewed by 8581

Abstract

Hyperbranched polyimide–silica hybrids (HBPI–silica HBDs) and hyperbranched polyimide–silica composites (HBPI–silica CPTs) were prepared, and their general and gas transport properties were investigated to clarify the effect of silica sources and preparation methods. HBPI–silica HBDs and HBPI–silica CPTs were synthesized by two-step polymerization of [...] Read more.

Hyperbranched polyimide–silica hybrids (HBPI–silica HBDs) and hyperbranched polyimide–silica composites (HBPI–silica CPTs) were prepared, and their general and gas transport properties were investigated to clarify the effect of silica sources and preparation methods. HBPI–silica HBDs and HBPI–silica CPTs were synthesized by two-step polymerization of A₂ + B₃ monomer system via polyamic acid as precursor, followed by hybridizing or blending silica sources. Silica components were incorporated by the sol-gel reaction with tetramethoxysilane (TMOS) or the addition of colloidal silica. In HBPI-silica HBDs, the aggregation of silica components is controlled because of the high affinity of HBPI and silica caused by the formation of covalent bonds between HBPI and silica. Consequently, HBPI-silica HBDs had good film formability, transparency, and mechanical properties compared with HBPI-silica CPTs. HBPI-silica HBD and CPT membranes prepared via the sol-gel reaction with TMOS showed specific gas permeabilities and permselectivities for CO₂/CH₄ separation, that is, both CO₂ permeability and CO₂/CH₄ selectivity increased with increasing silica content. This result suggests that gas transport can occur through a molecular sieving effect of the porous silica network derived from the sol-gel reaction and/or through the narrow interfacial region between the silica networks and the organic matrix. Full article

(This article belongs to the Special Issue Polymer Thin Films and Membranes 2013)

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627 KiB

Open AccessArticle

Strengthening of RC Slabs with Symmetric Openings Using GFRP Composite Beams

by Yeol Choi, Ik Hyun Park, Sang Goo Kang and Chang-Geun Cho

Polymers 2013, 5(4), 1352-1361; https://doi.org/10.3390/polym5041352 - 3 Dec 2013

Cited by 13 | Viewed by 8776

Abstract

This paper describes the results of experimental testing of glass fiber reinforced plastic (GFRP) composite beam strengthened reinforced concrete (RC) slabs with two symmetrical openings. Specimens, one-half scale, have been designed and fabricated to reflect the most common RC bathroom slab used in [...] Read more.

This paper describes the results of experimental testing of glass fiber reinforced plastic (GFRP) composite beam strengthened reinforced concrete (RC) slabs with two symmetrical openings. Specimens, one-half scale, have been designed and fabricated to reflect the most common RC bathroom slab used in school buildings. The specimen had dimensions of 2000 mm (width) × 150 mm (thickness) × 3000 mm (length) were used with the two openings of 300 mm × 400 mm. The aim of this study is to investigate the most effective strengthening method using GFRP composite beams in slabs with openings for enhancing the load-carrying capacity and stiffness. Test results showed that the strengthened slabs seems to increase the load-carrying capacity by 29%, 21% and 12% over that of the control specimen for diagonal, parallel and surround strengthening respectively. Furthermore, test results showed that the diagonal-strengthened system is one of the most effective methods for strengthening an RC slab with openings in terms of load-carrying capacity, stiffness and crack patterns. Full article

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

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791 KiB

Open AccessArticle

Influence of Glutamic Acid on the Properties of Poly(xylitol glutamate sebacate) Bioelastomer

by Weifu Dong, Ting Li, Shuangfei Xiang, Piming Ma and Mingqing Chen

Polymers 2013, 5(4), 1339-1351; https://doi.org/10.3390/polym5041339 - 29 Nov 2013

Cited by 14 | Viewed by 9150

Abstract

In order to further improve the biocompatibility of xylitol based poly(xylitol sebacate) (PXS) bioelastomer, a novel kind of amino acid based poly(xylitol glutamate sebacate) (PXGS) has been successfully prepared in this work by melt polycondensation of xylitol, N-Boc glutamic acid and sebacic [...] Read more.

In order to further improve the biocompatibility of xylitol based poly(xylitol sebacate) (PXS) bioelastomer, a novel kind of amino acid based poly(xylitol glutamate sebacate) (PXGS) has been successfully prepared in this work by melt polycondensation of xylitol, N-Boc glutamic acid and sebacic acid. Differential scanning calorimetry (DSC) results indicated the glass-transition temperatures could be decreased by feeding N-Boc glutamic acid. In comparison to PXS, PXGS exhibited comparable tensile strength and much higher elongation at break at the same ratio of acid/xylitol. The introduction of glutamic acid increased the hydrophilicity and in vitro degradation rate of the bioelastomer. It was found that PXGS exhibited excellent properties, such as tensile properties, biodegradability and hydrophilicity, which could be easily tuned by altering the feeding monomer ratios. The amino groups in the PXGS polyester side chains are readily functionalized, thus the biomelastomers can be considered as potential biomaterials for biomedical application. Full article

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2095 KiB

Open AccessArticle

Transparent Conductive Films Fabricated from Polythiophene Nanofibers Composited with Conventional Polymers

by Borjigin Aronggaowa, Yuriko Toda, Noriyuki Ito, Kazuhiro Shikinaka and Takeshi Shimomura

Polymers 2013, 5(4), 1325-1338; https://doi.org/10.3390/polym5041325 - 19 Nov 2013

Cited by 13 | Viewed by 7950

Abstract

Transparent, conductive films were prepared by compositing poly(3-hexylthiophene) (P3HT) nanofibers with poly(methyl methacrylate) (PMMA). The transparency, conductivity, atmospheric stability, and mechanical strength of the resulting nanofiber composite films when doped with AuCl₃ were evaluated and compared with those of P3HT nanofiber mats. [...] Read more.

Transparent, conductive films were prepared by compositing poly(3-hexylthiophene) (P3HT) nanofibers with poly(methyl methacrylate) (PMMA). The transparency, conductivity, atmospheric stability, and mechanical strength of the resulting nanofiber composite films when doped with AuCl₃ were evaluated and compared with those of P3HT nanofiber mats. The conductivity of the nanofiber composite films was 4.1 S∙cm⁻¹, which is about seven times lessthan that which was previously reported for a nanofiber mat with the same optical transmittance (~80%) reported by Aronggaowa et al. The time dependence of the transmittance, however, showed that the doping state of the nanofiber composite films in air was more stable than that of the nanofiber mats. The fracture stress of the nanofiber composite film was determined to be 12.3 MPa at 3.8% strain. Full article

(This article belongs to the Special Issue Semiconducting Polymers for Organic Electronic Devices)

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19078 KiB

Open AccessReview

Structure and Morphology Control in Thin Films of Conjugated Polymers for an Improved Charge Transport

by Haiyang Wang, Yaozhuo Xu, Xinhong Yu, Rubo Xing, Jiangang Liu and Yanchun Han

Polymers 2013, 5(4), 1272-1324; https://doi.org/10.3390/polym5041272 - 18 Nov 2013

Cited by 93 | Viewed by 25799

Abstract

The morphological and structural features of the conjugated polymer films play an important role in the charge transport and the final performance of organic optoelectronics devices [such as organic thin-film transistor (OTFT) and organic photovoltaic cell (OPV), etc.] in terms of crystallinity, [...] Read more.

The morphological and structural features of the conjugated polymer films play an important role in the charge transport and the final performance of organic optoelectronics devices [such as organic thin-film transistor (OTFT) and organic photovoltaic cell (OPV), etc.] in terms of crystallinity, packing of polymer chains and connection between crystal domains. This review will discuss how the conjugated polymer solidify into, for instance, thin-film structures, and how to control the molecular arrangement of such functional polymer architectures by controlling the polymer chain rigidity, polymer solution aggregation, suitable processing procedures, etc. These basic elements in intrinsic properties and processing strategy described here would be helpful to understand the correlation between morphology and charge transport properties and guide the preparation of efficient functional conjugated polymer films correspondingly. Full article

(This article belongs to the Special Issue Semiconducting Polymers for Organic Electronic Devices)

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318 KiB

Open AccessArticle

The Glycolysis of Poly(ethylene terephthalate) Waste: Lewis Acidic Ionic Liquids as High Efficient Catalysts

by Qun Feng Yue, Lin Fei Xiao, Mi Lin Zhang and Xue Feng Bai

Polymers 2013, 5(4), 1258-1271; https://doi.org/10.3390/polym5041258 - 13 Nov 2013

Cited by 96 | Viewed by 12596

Abstract

Poly(ethlyene terephthalate) waste from a local market was depolymerized by ethylene glycol (EG) in the presence of Lewis acidic ionic liquids [Bmim]ZnCl₃ and the qualitative analysis showed that bis(hydroxyethyl) terephthalate was the main product. Compared with ionic liquid [Bmim]Cl, the Lewis acidic [...] Read more.

Poly(ethlyene terephthalate) waste from a local market was depolymerized by ethylene glycol (EG) in the presence of Lewis acidic ionic liquids [Bmim]ZnCl₃ and the qualitative analysis showed that bis(hydroxyethyl) terephthalate was the main product. Compared with ionic liquid [Bmim]Cl, the Lewis acidic ionic liquids showed highly catalytic activity in the glycolysis of poly(ethylene terephthalate) PET. Significantly, the conversion of PET and the yield of bis(hydroxyethyl) terephthalate were achieved at 100% and 83.8% with low catalyst ([Bmim]ZnCl₃) loading (0.16 wt %). Investigation also showed that the catalytic activity of [Bmim]ZnCl₃ was higher than that of [Bmim]MnCl₃. Catalyst [Bmim]ZnCl₃ can be reused up to five times and ¹H-NMR results show that the recovered catalyst is similar to the fresh one. A mechanism of the glycolysis of PET catalyzed by [Bmim]ZnCl₃ was proposed. Full article

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582 KiB

Open AccessArticle

Release of Potassium Ion and Calcium Ion from Phosphorylcholine Group Bearing Hydrogels

by Hanna R. Aucoin, A. Nolan Wilson, Ann M. Wilson, Kazuhiko Ishihara and Anthony Guiseppi-Elie

Polymers 2013, 5(4), 1241-1257; https://doi.org/10.3390/polym5041241 - 11 Nov 2013

Cited by 29 | Viewed by 9773

Abstract

In an attempt to recreate the microenvironment necessary for directed hematopoietic stem cell differentiation, control over the amount of ions available to the cells is necessary. The release of potassium ion and calcium ion via the control of cross-linking density of a poly(2-hydroxyethyl [...] Read more.

In an attempt to recreate the microenvironment necessary for directed hematopoietic stem cell differentiation, control over the amount of ions available to the cells is necessary. The release of potassium ion and calcium ion via the control of cross-linking density of a poly(2-hydroxyethyl methacrylate) (pHEMA)-based hydrogel containing 1 mol % 2-methacryloyloxyethyl phosphorylcholine (MPC) and 5 mol % oligo(ethylene glycol) (400) monomethacrylate [OEG(400)MA] was investigated. Tetra(ethylene glycol) diacrylate (TEGDA), the cross-linker, was varied over the range of 1–12 mol %. Hydrogel discs (ϕ = 4.5 mm and h = 2.0 mm) were formed by UV polymerization within silicone isolators to contain 1.0 M CaCl₂ and 0.1 M KCl, respectively. Isothermal release profiles, were measured at 37 °C in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid sodium salt (HEPES) buffer using either calcium ion or potassium ion selective electrodes (ISE). The resulting release profiles were found to be independent of cross-linking density. Average (n = 3) release profiles were fit to five different release models with the Korsmeyer-Peppas equation, a porous media transport model, exhibiting the greatest correlation (R² > 0.95). The diffusion exponent, n was calculated to be 0.24 ± 0.02 and 0.36 ± 0.04 for calcium ion and potassium ion respectively indicating non-Fickian diffusion. The resulting diffusion coefficients were calculated to be 2.6 × 10⁻⁶ and 11.2 × 10⁻⁶ cm²/s, which compare well to literature values of 2.25 × 10⁻⁶ and 19.2 × 10⁻⁶ cm²/s for calcium ion and potassium ion, respectively. Full article

(This article belongs to the Special Issue Biomimetic Polymers)

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1237 KiB

Open AccessArticle

Surface Initiated Polymerizations via e-ATRP in Pure Water

by Seyed Schwan Hosseiny and Patrick Van Rijn

Polymers 2013, 5(4), 1229-1240; https://doi.org/10.3390/polym5041229 - 25 Oct 2013

Cited by 27 | Viewed by 9571

Abstract

Here we describe the combined process of surface modification with electrochemical atom transfer radical polymerization (e-ATRP) initiated from the surface of a modified gold-electrode in a pure aqueous solution without any additional supporting electrolyte. This approach allows for a very controlled [...] Read more.

Here we describe the combined process of surface modification with electrochemical atom transfer radical polymerization (e-ATRP) initiated from the surface of a modified gold-electrode in a pure aqueous solution without any additional supporting electrolyte. This approach allows for a very controlled growth of the polymer chains leading towards a steady increase in film thickness. Electrochemical quartz crystal microbalance displayed a highly regular increase in surface confined mass only after the addition of the pre-copper catalyst which is reduced in situ and transformed into the catalyst. Even after isolation and washing of the modified electrode surface, reinitiation was achieved with retention of the controlled electrochemical ATRP reaction. This reinitiation after isolation proves the livingness of the polymerization. This approach has interesting potential for smart thin film materials and offers also the possibility of post-modification via additional electrochemical induced reactions. Full article

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961 KiB

Open AccessArticle

Preparation and Characterization of Molecularly Imprinted Polymer as SPE Sorbent for Melamine Isolation

by Nor Azah Yusof, Siti Khadijah Ab. Rahman, Mohd Zobir Hussein and Nor Azowa Ibrahim

Polymers 2013, 5(4), 1215-1228; https://doi.org/10.3390/polym5041215 - 23 Oct 2013

Cited by 89 | Viewed by 12132

Abstract

In this paper, a separation procedure combining molecularly imprinted-solid phase extraction (MI-SPE) was developed for the isolation of melamine. The molecularly imprinted polymer (MIP) was prepared using precipitation polymerization method where melamine as template, 9-vinylcarbazole as functional monomer, ethtylene glycol dimethacrylate as a [...] Read more.

In this paper, a separation procedure combining molecularly imprinted-solid phase extraction (MI-SPE) was developed for the isolation of melamine. The molecularly imprinted polymer (MIP) was prepared using precipitation polymerization method where melamine as template, 9-vinylcarbazole as functional monomer, ethtylene glycol dimethacrylate as a cross-linker and benzoyl peroxide as initiator. An off-line MI-SPE method followed by ultra-performance liquid chromatography detection of melamine was established. MIP showed a better affinity toward melamine compared to non imprinted polymer (NIP) with a maximum binding capacity of 53.01 mg/g MIP. Based on the correlation coefficients, the kinetic study indicated that the adsorption of melamine by MIP fit a pseudo-second order model. From isotherm study, adsorption of melamine by MIP increased when the concentration of melamine increased and followed a Freundlich isotherm model, which indicates the sorption can be described by multilayer sorption. The interference study proved that MIP has better binding capacity towards melamine if compared to NIP due to specific sites of melamine occurred in MIP particles. Full article

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290 KiB

Open AccessArticle

Hydrophobic Poly(ionic liquid) for Highly Effective Separation of Methyl Blue and Chromium Ions from Water

by Hao Mi, Zhiguo Jiang and Jie Kong

Polymers 2013, 5(4), 1203-1214; https://doi.org/10.3390/polym5041203 - 14 Oct 2013

Cited by 59 | Viewed by 12127

Abstract

The hydrophobic poly(ionic liquid) of poly(3-ethyl-1-vinylimidazolium bis(trifluoromethanesulfonyl)imide) (PVI-TFSI) containing imidazolium cations and bis(trifluoromethanesulfonyl)imide anions was synthesized for the separation of methyl blue and chromium ions [Cr(VI)] from water. The adsorption of methyl blue and Cr(VI) in PVI-TSFI/water system reached equilibrium stage within 60 [...] Read more.

The hydrophobic poly(ionic liquid) of poly(3-ethyl-1-vinylimidazolium bis(trifluoromethanesulfonyl)imide) (PVI-TFSI) containing imidazolium cations and bis(trifluoromethanesulfonyl)imide anions was synthesized for the separation of methyl blue and chromium ions [Cr(VI)] from water. The adsorption of methyl blue and Cr(VI) in PVI-TSFI/water system reached equilibrium stage within 60 min and 12 h, and the maximum adsorbed percentage for methyl blue and Cr(VI) was 97.6% and 98.0%, respectively. The adsorption regi me of either methyl blue or Cr(VI) for PVI-TFSI was in correspondence with the Langmuir adsorption model. The maximum adsorption capacity of PVI-TFSI for methyl blue and Cr(VI) was determined as 476.2 and 17.9 mg/g, respectively. The hydrophobic poly(ionic liquid) with a remarkable adsorbent capacity of methyl blue and Cr(VI) can be conveniently synthesized and shows potential in water treatment for the effective separation of organic dyes or heavy metal ions. Full article

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5343 KiB

Open AccessReview

Mechanisms of the Shape Memory Effect in Polymeric Materials

by Xuelian Wu, Wei Min Huang, Yong Zhao, Zheng Ding, Cheng Tang and Jiliang Zhang

Polymers 2013, 5(4), 1169-1202; https://doi.org/10.3390/polym5041169 - 30 Sep 2013

Cited by 109 | Viewed by 21410

Abstract

This review paper summarizes the recent research progress in the underlying mechanisms behind the shape memory effect (SME) and some newly discovered shape memory phenomena in polymeric materials. It is revealed that most polymeric materials, if not all, intrinsically have the thermo/chemo-responsive SME. [...] Read more.

This review paper summarizes the recent research progress in the underlying mechanisms behind the shape memory effect (SME) and some newly discovered shape memory phenomena in polymeric materials. It is revealed that most polymeric materials, if not all, intrinsically have the thermo/chemo-responsive SME. It is demonstrated that a good understanding of the fundamentals behind various types of shape memory phenomena in polymeric materials is not only useful in design/synthesis of new polymeric shape memory materials (SMMs) with tailored performance, but also helpful in optimization of the existing ones, and thus remarkably widens the application field of polymeric SMMs. Full article

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Polymers, Volume 5, Issue 4 (December 2013) – 12 articles , Pages 1169-1391

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