Polymers

5901 KiB

Open AccessFeature PaperArticle

New Proposal for Flexural Strengthening of Reinforced Concrete Beams Using CFRP T-Shaped Profiles

by Renata Kotynia and Szymon Cholostiakow

Polymers 2015, 7(11), 2461-2477; https://doi.org/10.3390/polym7111524 - 24 Nov 2015

Cited by 20 | Viewed by 7948

The purpose of this study was to evaluate the performance of a novel strengthening system using T-shaped carbon fiber reinforced polymer (CFRP) profiles. The proposed system successfully combines the advantages of two established strengthening techniques, namely the near surface mounted (NSM) and externally [...] Read more.

The purpose of this study was to evaluate the performance of a novel strengthening system using T-shaped carbon fiber reinforced polymer (CFRP) profiles. The proposed system successfully combines the advantages of two established strengthening techniques, namely the near surface mounted (NSM) and externally bonded (EB) methods. The paper presents the experimental results of structural tests carried out on seven flexurally-strengthened and two non-strengthened full-scale reinforced concrete (RC) members. Two T-shaped profiles having heights of 15 and 30 mm were applied. The main parameters of concrete strength and composite strengthening ratio were investigated to evaluate the efficiency of the proposed flexural strengthening system. All specimens were tested under a quasi-static six-point bending configuration. The test results showed a significant increase in the load bearing capacity and the stiffness of the RC beams with strengthening and also a notable reduction in maximum deflections. The high tensile strength utilization of the CFRP profiles places this strengthening technique as a promising alternative to other, less structurally-efficient systems. Full article

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

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5575 KiB

Open AccessArticle

Quantitative Phase Fraction Detection in Organic Photovoltaic Materials through EELS Imaging

by Ondrej Dyck, Sheng Hu, Sanjib Das, Jong Keum, Kai Xiao, Bamin Khomami and Gerd Duscher

Polymers 2015, 7(11), 2446-2460; https://doi.org/10.3390/polym7111523 - 24 Nov 2015

Cited by 16 | Viewed by 6162

Abstract

Organic photovoltaic materials have recently seen intense interest from the research community. Improvements in device performance are occurring at an impressive rate; however, visualization of the active layer phase separation still remains a challenge. This paper outlines the application of two electron energy-loss [...] Read more.

Organic photovoltaic materials have recently seen intense interest from the research community. Improvements in device performance are occurring at an impressive rate; however, visualization of the active layer phase separation still remains a challenge. This paper outlines the application of two electron energy-loss spectroscopic (EELS) imaging techniques that can complement and enhance current phase detection techniques. Specifically, the bulk plasmon peak position, often used to produce contrast between phases in energy filtered transmission electron microscopy (EFTEM), is quantitatively mapped across a sample cross section. A complementary spectrum image capturing the carbon and sulfur core loss edges is compared with the plasmon peak map and found to agree quite well, indicating that carbon and sulfur density differences between the two phases also allows phase discrimination. Additionally, an analytical technique for determining absolute atomic areal density is used to produce an absolute carbon and sulfur areal density map. We show how these maps may be re-interpreted as a phase ratio map, giving quantitative information about the purity of the phases within the junction. Full article

(This article belongs to the Special Issue Organic Photovoltaics)

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11979 KiB

Open AccessArticle

Preparation and Characteristics of Corn Straw-Co-AMPS-Co-AA Superabsorbent Hydrogel

by Wei-Min Cheng, Xiang-Ming Hu, De-Ming Wang and Guo-Hua Liu

Polymers 2015, 7(11), 2431-2445; https://doi.org/10.3390/polym7111522 - 24 Nov 2015

Cited by 49 | Viewed by 8576

Abstract

In this study, the corn straw after removing the lignin was grafted with 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to prepare sulfonated cellulose. The grafting copolymerization between the sulfonated cellulose and acrylic acid (AA) was performed using potassium persulfate and N,N′-methylenebisacrylamide as the [...] Read more.

In this study, the corn straw after removing the lignin was grafted with 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to prepare sulfonated cellulose. The grafting copolymerization between the sulfonated cellulose and acrylic acid (AA) was performed using potassium persulfate and N,N′-methylenebisacrylamide as the initiator and crosslinking agent, respectively, to prepare corn straw-co-AMPS-co-AA hydrogels. The structure and properties of the resulting hydrogels were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and dynamic rheometry. The effects of initiator, crosslinker, monomer neutralization degree, and temperature on the swelling ratio of the hydrogels were studied. The water retention, salt resistance, and recyclability of the corn straw-co-AMPS-co-AA hydrogels were also investigated. The optimum water absorptivity of the corn straw hydrogels was obtained at a polymerization temperature of 50 °C with 1.2% crosslinker, 1:7 ratio of the pretreated corn straw and AA, 2% initiator, and 50% neutralized AA. Full article

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9168 KiB

Open AccessArticle

Epirubicin-Complexed Polypeptide Micelle Effectively and Safely Treats Hepatocellular Carcinoma

by Qinglin Zhang, Jianxun Ding, Chenwei Lv, Weiguo Xu, Xun Sun and Xiangwei Meng

Polymers 2015, 7(11), 2410-2430; https://doi.org/10.3390/polym7111521 - 24 Nov 2015

Cited by 19 | Viewed by 9684

Abstract

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related mortality worldwide. Epirubicin (EPI) once acted as a main agent for HCC chemotherapy. However, the dosage-dependent side effects seriously limit its application in clinic. The purpose of this study is to develop an [...] Read more.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related mortality worldwide. Epirubicin (EPI) once acted as a main agent for HCC chemotherapy. However, the dosage-dependent side effects seriously limit its application in clinic. The purpose of this study is to develop an effective nanocarrier to improve the efficacy and overcome the limitations of EPI. In this regard, the EPI-complexed micelle (i.e., mPEG-b-PGA/EPI) was prepared via the electrostatic interaction between the amino group in EPI and the carboxyl group in PGA segment of methoxy poly(ethylene glycol)-block-poly(l-glutamic acid) (mPEG-b-PGA), and the subsequent hydrophobic interaction among PGA/EPI complexes. The micelle appeared spherical with a diameter at around 90 nm and possessed a pH-sensitive release property of payload. The cytotoxicity and hemolysis assays in vitro, and the maximum tolerated dose tests in vivo confirmed that mPEG-b-PGA was a kind of safe material with excellent biocompatibility, while the drug-loaded micelle could obviously improve the tolerance of EPI. In addition, mPEG-b-PGA/EPI possessed significantly enhanced antitumor efficacy and security toward the H22-xenografted HCC murine model at macroscopic and microscopic levels compared with free EPI. All these results strongly indicate that mPEG-b-PGA/EPI may be a promising nanoplatform for EPI delivery in the chemotherapy of HCC. Full article

(This article belongs to the Special Issue Functional Polymers for Medical Applications)

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8876 KiB

Open AccessArticle

Stable Failure-Inducing Micro-Silica Aqua Epoxy Bonding Material for Floating Concrete Module Connection

by Jang-Ho Jay Kim, Young-Jun You, Youn-Ju Jeong and Ji-Hun Choi

Polymers 2015, 7(11), 2389-2409; https://doi.org/10.3390/polym7111520 - 24 Nov 2015

Cited by 5 | Viewed by 6317

Abstract

Many recent studies in the development of floating concrete structures focused on a connection system made of modules. In the connection system, the modules are designed to be attached by pre-stressing (PS) while floating on the water, which exposes them to loads on [...] Read more.

Many recent studies in the development of floating concrete structures focused on a connection system made of modules. In the connection system, the modules are designed to be attached by pre-stressing (PS) while floating on the water, which exposes them to loads on the surface of the water. Therefore, the development of a pre-connection material becomes critical to ensure successful bonding of floating concrete modules. Micro-silica mixed aqua-epoxy (MSAE) was developed for this task. To find the proper MSAE mix proportion, 0% to 4% micro-silica was mixed in a standard mixture of aqua-epoxy for material testing. Also, the effect of micro-silica on the viscosity of the aqua epoxy was evaluated by controlling the epoxy silane at proportions of 0%, ±5%, and ±10%. After completion of the performance tests of the MSAE, we evaluated the effect of MSAE in a connected structure. The plain unreinforced concrete module joint specimens applied with MSAE at thicknesses of 5, 10, and 20 mm were prepared to be tested. Finally, we evaluated the performance of MSAE-applied reinforced concrete (RC) module specimens connected by PS tendons, and these were compared with those of continuous RC and non-MSAE-applied beams. The results showed that the mix of micro-silica in the aqua-epoxy changed the performance of the aqua-epoxy and the mix ratio of 2% micro-silica gave a stable failure behavior. The flexural capacity of concrete blocks bonded with MSAE changed according to the bond thickness and was better than that of concrete blocks bonded with aqua-epoxy without micro-silica. Even though MSAE insignificantly increases the load-carrying capacity of the attached concrete module structure, the stress concentration reduction effect stabilized the failure of the structure. Full article

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

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3518 KiB

Open AccessArticle

Multi-Channeled Polymeric Microsystem for Studying the Impact of Surface Topography on Cell Adhesion and Motility

by Andres Diaz Lantada, Hernán Alarcón Iniesta and Josefa Predestinación García-Ruíz

Polymers 2015, 7(11), 2371-2388; https://doi.org/10.3390/polym7111519 - 23 Nov 2015

Cited by 3 | Viewed by 5705

Abstract

This paper presents the complete development and experimental validation of a microsystem designed to systematically assess the impact of surface topography on cell adhesion and dynamics. The microsystem includes two pools for culturing cells and for including chemicals. These pools are connected by [...] Read more.

This paper presents the complete development and experimental validation of a microsystem designed to systematically assess the impact of surface topography on cell adhesion and dynamics. The microsystem includes two pools for culturing cells and for including chemicals. These pools are connected by several channels that have different microtextures, along which the cells crawl from one well to another. The impact of channel surface topography on cell performance, as well as the influence of other relevant factors, can therefore be assessed. The microsystem stands out for its being able to precisely define the surface topographies from the design stage and also has the advantage of including the different textures under study in a single device. Validation has been carried out by culturing human mesenchymal stem cells (hMSCs) on the microsystem pre-treated with a coating of hMSC conditioned medium (CM) produced by these cells. The impact of surface topography on cell adhesion, motility, and velocity has been quantified, and the relevance of using a coating of hMSC-CM for these kinds of studies has been analyzed. Main results, current challenges, and future proposals based on the use of the proposed microsystem as an experimental resource for studying cell mechanobiology are also presented. Full article

(This article belongs to the Special Issue Polymers Applied in Tissue Engineering)

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14623 KiB

Open AccessReview

Switchable Materials Containing Polyzwitterion Moieties

by Markéta Ilčíková, Ján Tkáč and Peter Kasák

Polymers 2015, 7(11), 2344-2370; https://doi.org/10.3390/polym7111518 - 20 Nov 2015

Cited by 68 | Viewed by 11704

Abstract

In recent decades, the design and construction of smart materials capable of switching into a polyzwitterionic state by an external trigger have been intensively pursued. Polyzwitterionic states have unique antifouling and surface properties and external triggers, such as pH, light, ions, electric field [...] Read more.

In recent decades, the design and construction of smart materials capable of switching into a polyzwitterionic state by an external trigger have been intensively pursued. Polyzwitterionic states have unique antifouling and surface properties and external triggers, such as pH, light, ions, electric field and CO₂, cause significant changes in materials with regard to overall charge, ionic strength and wettability. This survey highlights current progress in the irreversible as well as the reversible switching process involving polyzwitterionic moieties, which can, in turn, be applied to studying the interaction of various interfaces with biological species as protein, DNA, bacteria or platelets and also for advanced use. Full article

(This article belongs to the Special Issue Functional Polymers for Medical Applications)

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4250 KiB

Open AccessArticle

Effect of Thermal Distress on Residual Behavior of CFRP-Strengthened Steel Beams Including Periodic Unbonded Zones

by Isamu Yoshitake, Hisatsugu Tsuda, Yail J. Kim and Nobuhiro Hisabe

Polymers 2015, 7(11), 2332-2343; https://doi.org/10.3390/polym7111517 - 17 Nov 2015

Cited by 4 | Viewed by 5447

Abstract

This paper presents the residual behavior of wide-flange steel beams strengthened with high-modulus carbon fiber-reinforced polymer (CFRP) laminates subjected to thermal loading. Because the coefficients of thermal expansion of the steel and the CFRP are different, temperature-induced distress may take place along their [...] Read more.

This paper presents the residual behavior of wide-flange steel beams strengthened with high-modulus carbon fiber-reinforced polymer (CFRP) laminates subjected to thermal loading. Because the coefficients of thermal expansion of the steel and the CFRP are different, temperature-induced distress may take place along their interface. Periodic unbonded zones are considered to represent local interfacial damage. Five test categories are designed depending on the size of the unbonded zones from 10 to 50 mm, and corresponding beams are loaded until failure occurs after exposing to a cyclic temperature range of ΔT = 25 °C (−10 to 15 °C) up to 84 days. The composite action between the CFRP and the steel substrate is preserved until yielding of the beams happens, regardless of the thermal cycling and periodic unbonded zones. The initiation and progression of CFRP debonding become apparent as the beams are further loaded, particularly at geometric discontinuities in the vicinity of the unbonded zones along the interface. A simple analytical model is employed to predict the interfacial stress of the strengthened beams. A threshold temperature difference of ΔT = 30 °C is estimated for the initiation and progression of CFRP debonding. Multiple debonding-progression stages in conjunction with the extent of thermal distress appear to exist. It is recommended that high-modulus CFRP be restrictively used for strengthening steel members potentially exposed to a wide temperature variation range. Full article

(This article belongs to the Special Issue Selected Papers from The 7th International Conference on FRP Composites in Civil Engineering (CICE 2014))

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3608 KiB

Open AccessArticle

Amino Acid-Modified Polyethylenimines with Enhanced Gene Delivery Efficiency and Biocompatibility

by Qin-Fang Zhang, Chao-Ran Luan, Dong-Xiao Yin, Ji Zhang, Yan-Hong Liu, Qi Peng, Yong Xu and Xiao-Qi Yu

Polymers 2015, 7(11), 2316-2331; https://doi.org/10.3390/polym7111516 - 17 Nov 2015

Cited by 15 | Viewed by 7859

Abstract

The development of gene delivery vectors with high efficiency and biocompatibility is one of the key points of gene therapy. A series of polycations were prepared from polyethylenimine (PEI) with several amino acids or their analogs. The target polymers have different charge and [...] Read more.

The development of gene delivery vectors with high efficiency and biocompatibility is one of the key points of gene therapy. A series of polycations were prepared from polyethylenimine (PEI) with several amino acids or their analogs. The target polymers have different charge and hydrophilic/hydrophobic properties, which may affect their performance in the gene transfection process. Gel retardation and DLS assays showed that these polymers may condense DNA into nanoparticles with positive zeta potentials and proper sizes for cellular uptake. Luciferase reporter gene transfection results revealed their higher transfection efficiency than PEI; especially in the presence of serum, in which up to 23 times higher efficiency was achieved by employing glycolic acid-grafted PEI. Moreover, it was found that the degree of substitution on PEI has an apparent influence on the transfection, and the balance between electron-positive/negative groups largely affects the delivery process. The higher serum tolerance was also proven by BSA adsorption, flow cytometry and confocal microscopy assays. Results demonstrate that such type of polycations may serve as promising non-viral gene delivery vectors. Full article

(This article belongs to the Special Issue Functional Polymers for Medical Applications)

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3055 KiB

Open AccessArticle

Leads from Physical, Chemical, and Thermal Characterization on Cytotoxic Effects of Xylan-Based Microparticles

by Henrique Rodrigues Marcelino, Acarília Eduardo Da Silva, Monique Christine Salgado Gomes, Elquio Eleamen Oliveira, Toshiyuki Nagashima-Junior, Gardênia Sousa Pinheiro, Acarízia Eduardo Da Silva, Ana Rafaela de Souza Timoteo, Lucymara Fassarela Agnez-Lima, Alejandro Pedro Ayala, Anselmo Gomes Oliveira and Eryvaldo Sócrates Tabosa Do Egito

Polymers 2015, 7(11), 2304-2315; https://doi.org/10.3390/polym7111515 - 16 Nov 2015

Cited by 16 | Viewed by 5427

Abstract

Interfacial cross-linking (ICL) has been considered a feasible technique to produce polysaccharide-based microparticles (PbMs), even though only a few studies have been concerned with their biocompatibility. In this work, PbMs were prepared by the ICL method and characterized in regard to their in [...] Read more.

Interfacial cross-linking (ICL) has been considered a feasible technique to produce polysaccharide-based microparticles (PbMs), even though only a few studies have been concerned with their biocompatibility. In this work, PbMs were prepared by the ICL method and characterized in regard to their in vitro biocompatibility, chemical linkages, and physical and thermal properties. First, the cell viability assay revealed that PbMs toxicity was concentration-dependent. Then, it was observed that the toxicity may be related to the way in which the binding occurred, and not exclusively to the stoichiometry between the polymer and the cross-linking agent. Moreover, the PbMs biosafety was predicted by the use of physicochemical procedures, which were able to identify unbound cross-linking agent residues and also to reveal the improvement of their thermal stability. Accordingly, this work suggests a step-by-step physicochemical procedure able to predict potential toxicity from micro-structured devices produced by polysaccharides. Likewise, the use of PbMs as a drug carrier should be cautiously considered. Full article

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Open AccessArticle

Antibacterial/Antiviral Property and Mechanism of Dual-Functional Quaternized Pyridinium-type Copolymer

by Yan Xue and Huining Xiao

Polymers 2015, 7(11), 2290-2303; https://doi.org/10.3390/polym7111514 - 11 Nov 2015

Cited by 44 | Viewed by 11282

Abstract

Due to the massive outbreaks of pathogen-caused diseases and the increase of drug-resistant pathogens, there is a particular interest in the development of novel disinfection agents with broad-spectrum antipathogenic activity. In the present study, water-soluble pyridinium-type polyvinylpyrrolidones with different counter anions were prepared. [...] Read more.

Due to the massive outbreaks of pathogen-caused diseases and the increase of drug-resistant pathogens, there is a particular interest in the development of novel disinfection agents with broad-spectrum antipathogenic activity. In the present study, water-soluble pyridinium-type polyvinylpyrrolidones with different counter anions were prepared. Structural characterization was conducted via 13C–1H heteronuclear single quantum coherence spectroscopy, static light scattering, UV spectrometry and apparent charge density. The influence of counter anion and polymer compositions on the antibacterial activity was studied against Staphylococcus aureus and Escherichia coli. Atomic force microscopy (AFM) was applied for tracking the morphological alterations in bacterial cells induced by prepared polycations. It was found that the exposure of bacteria to the polycations resulted in the destruction of cell membranes and the leakage of cytoplasm. The antiviral activity of pyridinium-type polycations against enveloped influenza virus was evaluated via a plaque assay. The action mode against enveloped virus was depicted to rationalize the antiviral mechanism. Full article

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Open AccessArticle

Thermal and Fire Characteristics of FRP Composites for Architectural Applications

by Umberto Berardi and Nicholas Dembsey

Polymers 2015, 7(11), 2276-2289; https://doi.org/10.3390/polym7111513 - 11 Nov 2015

Cited by 40 | Viewed by 9602

Abstract

This paper discusses the main challenges of using fiber reinforced polymers (FRPs) in architectural applications. Architects are showing increased interest in the use of FRPs in modern buildings thanks to FRPs’ ability to allow cost effective realization of unique shapes and flexible aesthetics, [...] Read more.

This paper discusses the main challenges of using fiber reinforced polymers (FRPs) in architectural applications. Architects are showing increased interest in the use of FRPs in modern buildings thanks to FRPs’ ability to allow cost effective realization of unique shapes and flexible aesthetics, while accommodating architectural designs and needs. The long-term durability, weathering resistance, and the exceptional mechanical properties have recently suggested the adoption of FRPs for building façade systems in an increasing number of buildings worldwide. However, some challenges for a wider adoption of FRPs in buildings are represented by the environmental and thermal aspects of their production, as well as their resistance to the expected “fire loads”. This last aspect often raises many concerns, which often require expensive fire tests. In this paper, the results of cone calorimeter tests are compared with software simulations to evaluate the possibility of designing FRPs on the computer as opposed to current design practice that involves iterative use of fire testing. The comparison shows that pyrolysis simulations related to FRPs are still not an effective way to design fire safe FRPs for architectural applications. Full article

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Open AccessArticle

Intraoral Temperature Triggered Shape-Memory Effect and Sealing Capability of A Transpolyisoprene-Based Polymer

by Gakuji Tsukada, Ryuzo Kato, Masayuki Tokuda and Yoshihiro Nishitani

Polymers 2015, 7(11), 2259-2275; https://doi.org/10.3390/polym7111512 - 09 Nov 2015

Cited by 11 | Viewed by 7574

Abstract

In dentistry, pure gutta-percha (trans-1,4-polyisoprene (TPI)) is widely used as a main component of root canal filling materials. TPI has an interesting shape memory formed through cross-linking, and this characteristic is expected to be very effective for development of novel dental treatments; in [...] Read more.

In dentistry, pure gutta-percha (trans-1,4-polyisoprene (TPI)) is widely used as a main component of root canal filling materials. TPI has an interesting shape memory formed through cross-linking, and this characteristic is expected to be very effective for development of novel dental treatments; in particular, modification of the shape recovery temperature to the intraoral temperature (37 °C) will enhance the applicability of the shape-memory effect of TPI in root canal filling. In this study, trial test specimens consisting of varying proportions of TPI, cis-polyisoprene, zinc oxide, stearic acid, sulfur and dicumyl peroxide were prepared and the temperature dependence of their shape recovery, recovery stress and relaxation modulus were measured. Additionally, their sealing abilities were tested using glass tubing and a bovine incisor. As the ratio of cross-linking agent in the specimens increased, a decrease in recovery temperature and an increase in recovery stress and recovery speed were observed. In addition, the test specimen containing the highest concentration of cross-linking agent showed superior sealing ability under a thermal stimulus of 37 °C in both sealing ability tests. Full article

(This article belongs to the Special Issue Shape-Memory Polymers)

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4363 KiB

Open AccessArticle

Bioreducible Micelles Self-Assembled from Poly(ethylene glycol)-Cholesteryl Conjugate As a Drug Delivery Platform

by Chulsu Baek, Tae-Lin Ha, Eunjoo Kim, Sang Won Jeong, Se Guen Lee, Sung Jun Lee and Hyun-Chul Kim

Polymers 2015, 7(11), 2245-2258; https://doi.org/10.3390/polym7111511 - 06 Nov 2015

Cited by 5 | Viewed by 8359

Abstract

The ability of polymeric micelles to self-assemble into nanosized particles has created interest in their application as potential anticancer drug delivery systems. A poly(ethylene glycol)-cholesteryl conjugate (Chol-ss-PEG-ss-Chol) connected by cleavable disulfide linkages was synthesized and used as a nanocarrier for in vitro release [...] Read more.

The ability of polymeric micelles to self-assemble into nanosized particles has created interest in their application as potential anticancer drug delivery systems. A poly(ethylene glycol)-cholesteryl conjugate (Chol-ss-PEG-ss-Chol) connected by cleavable disulfide linkages was synthesized and used as a nanocarrier for in vitro release of doxorubicin (DOX). Owing to its amphiphilic structure, Chol-ss-PEG-ss-Chol was able to self-assemble into micelles with an average diameter 18.6 nm in aqueous solution. The micelles formed large aggregates due to the shedding of the PEG shell through cleavage of disulfide bonds in a reductive environment. The in vitro release studies revealed that Chol-ss-PEG-ss-Chol micelles released 80% and approximately 9% of the encapsulated DOX within 6 h under reductive and non-reductive conditions, respectively. The glutathione (GSH)-mediated intracellular drug delivery was investigated in a KB cell line. The cytotoxicity of DOX-loaded micelles indicated a higher cellular anti-proliferative effect against GSH-pretreated than untreated KB cells. Furthermore, confocal laser scanning microscopy (CLSM) measurement demonstrated that Chol-ss-PEG-ss-Chol micelles exhibited faster drug release in GSH-pretreated KB cells than untreated KB cells. These results suggest the potential usefulness of disulfide-based polymeric micelles as controlled drug delivery carriers. Full article

(This article belongs to the Special Issue Stimuli-Responsive Polymers and Colloids)

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4477 KiB

Open AccessArticle

The Effect of β-Glycerophosphate Crosslinking on Chitosan Cytotoxicity and Properties of Hydrogels for Vaginal Application

by Emilia Szymaǹska, Katarzyna Sosnowska, Wojciech Miltyk, Małgorzata Rusak, Anna Basa and Katarzyna Winnicka

Polymers 2015, 7(11), 2223-2244; https://doi.org/10.3390/polym7111510 - 04 Nov 2015

Cited by 33 | Viewed by 9553

Abstract

Mucoadhesive gelling systems based on chitosan and chitosan/β-glycerophosphate (β-GP) were developed in order to increase clotrimazole residence time in the vaginal cavity. Ex vivo mucoadhesiveness using porcine vaginal mucosa followed with mechanical, viscoelastic, and swelling properties of prepared hydrogels were evaluated. Drug-free, sterile, [...] Read more.

Mucoadhesive gelling systems based on chitosan and chitosan/β-glycerophosphate (β-GP) were developed in order to increase clotrimazole residence time in the vaginal cavity. Ex vivo mucoadhesiveness using porcine vaginal mucosa followed with mechanical, viscoelastic, and swelling properties of prepared hydrogels were evaluated. Drug-free, sterile, unmodified, and β-GP crosslinked chitosan were investigated for the in vitro cytotoxicity in CRL 2616 human vaginal mucosa cells using MTT assay, fluorescent microscopy, and flow cytometry analysis. Chitosan/β-GP hydrogels exhibited pseudoplastic and thixotropic properties. Ionic interaction between β-GP and chitosan improved mechanical properties of hydrogels in terms of hardness, cohesiveness, and compressibility. The hydrogels’ ability to interact with porcine vaginal mucosa (measured as force of detachment and work of adhesion) was comparable to those obtained with reference mucoadhesive gel Replens™. Surprisingly, greater mucoadhesive properties were noticed for chitosan/β-GP hydrogels. The cytotoxic effect of unmodified and β-GP crosslinked chitosan was hardly affected by chitosan molecular weight, exhibited mainly through inducing apoptosis, and was found to be significantly lower in the presence of chitosan/β-GP. Furthermore, the higher amount of β-GP was used to crosslink chitosan, the lower cytotoxic effect was observed. Full article

(This article belongs to the Collection Polysaccharides)

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Open AccessReview

A Review of Natural Fiber Reinforced Poly(Vinyl Alcohol) Based Composites: Application and Opportunity

by Boon Khoon Tan, Yern Chee Ching, Sin Chew Poh, Luqman Chuah Abdullah and Seng Neon Gan

Polymers 2015, 7(11), 2205-2222; https://doi.org/10.3390/polym7111509 - 02 Nov 2015

Cited by 141 | Viewed by 15847

Abstract

Natural fibers are fine examples of renewable resources that play an important role in the composites industry, which produces superior strength comparable to synthetic fibers. Poly(vinyl alcohol) (PVA) composites in particular have attracted enormous interest in view of their satisfactory performance, properties and [...] Read more.

Natural fibers are fine examples of renewable resources that play an important role in the composites industry, which produces superior strength comparable to synthetic fibers. Poly(vinyl alcohol) (PVA) composites in particular have attracted enormous interest in view of their satisfactory performance, properties and biodegradability. Their performance in many applications such as consumer, biomedical, and agriculture is well defined and promising. This paper reviews the utilization of natural fibers from macro to nanoscale as reinforcement in PVA composites. An overview on the properties, processing methods, biodegradability, and applications of these composites is presented. The advantages arising from chemical and physical modifications of fibers or composites are discussed in terms of improved properties and performance. In addition, proper arrangement of nanocellulose in composites helps to prevent agglomeration and results in a better dispersion. The limitations and challenges of the composites and future works of these bio-composites are also discussed. This review concludes that PVA composites have potential for use in numerous applications. However, issues on technological feasibility, environmental effectiveness, and economic affordability should be considered. Full article

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Open AccessArticle

Viscoelastic, Spectroscopic and Microscopic Study of the Photo Irradiation Effect on the Stability of PVC in the Presence of Sulfamethoxazole Schiff’s Bases

by Emad Yousif, Gamal A. El-Hiti, Zainab Hussain and Ali Altaie

Polymers 2015, 7(11), 2190-2204; https://doi.org/10.3390/polym7111508 - 02 Nov 2015

Cited by 45 | Viewed by 7023

Abstract

The photostabilization of poly(vinyl chloride) (PVC) films having five Schiff’s bases derived from sulphamethoxazole has been investigated. The casting method was used to produce PVC films containing sulphamethoxazoles (0.5% by weight), in tetrahydrofuran. The photostabilization activities of five additives were determined by monitoring [...] Read more.

The photostabilization of poly(vinyl chloride) (PVC) films having five Schiff’s bases derived from sulphamethoxazole has been investigated. The casting method was used to produce PVC films containing sulphamethoxazoles (0.5% by weight), in tetrahydrofuran. The photostabilization activities of five additives were determined by monitoring the hydroxyl, polyene and carbonyl indices with irradiation time. In addition, the quantum yield of the chain scission (Φcs) and the changes in viscosity average molecular weight of PVC films containing Schiff’s basses were evaluated with irradiation time. The rate of photostabilization for PVC films in the presence of five Schiff’s base additives was found to be the highest in the case of 2-hydroxybenzylidene derivative and the lowest in the unsubstituted benzylidene derivative. Several mechanisms have been suggested to explain the photostabilization of PVC in the presence of Schiff’s bases that mainly act as UV absorbers and radical scavengers for photostabilizers. Full article

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2386 KiB

Open AccessArticle

Non-Isothermal Cold-Crystallization Behavior and Kinetics of Poly(l-Lactic Acid)/WS₂ Inorganic Nanotube Nanocomposites

by Mohammed Naffakh, Carlos Marco and Gary Ellis

Polymers 2015, 7(11), 2175-2189; https://doi.org/10.3390/polym7111507 - 29 Oct 2015

Cited by 24 | Viewed by 6305

Abstract

In order to accelerate the crystallization of poly(l-lactic acid) (PLLA) biopolymer and enhance its crystallizability, biocompatible and environmentally friendly tungsten disulphide inorganic nanotubes (INT-WS₂) were introduced into the polymer matrix. The non-isothermal cold-crystallization and subsequent melting behaviour of pure PLLA and [...] Read more.

In order to accelerate the crystallization of poly(l-lactic acid) (PLLA) biopolymer and enhance its crystallizability, biocompatible and environmentally friendly tungsten disulphide inorganic nanotubes (INT-WS₂) were introduced into the polymer matrix. The non-isothermal cold-crystallization and subsequent melting behaviour of pure PLLA and PLLA/INT-WS₂ nanocomposites were investigated in detail by varying both the heating rate and INT-WS₂ loading. The kinetic parameters of the cold-crystallization process of PLLA chains under confined conditions, successfully described using Liu model, shows that the addition of INT-WS₂ significantly increased the crystallization rate and reduced the total cold-crystallinity of PLLA, while the crystallization mechanism and crystal structure of PLLA remained unchanged in spite of the INT-WS₂ loading. Similarly, the final crystallinity and melting behaviour of PLLA were controlled by both the incorporation INT-WS₂ and variation of the heating rate. The differential isoconversional method of Friedman was applied to estimate the dependence of the effective activation energy on the relative crystallinity and temperature for PLLA and PLLA/INT-WS₂. On the other hand, the double-melting peaks, mainly derived from melting-recrystallization-melting processes upon heating, and their dynamic behaviour is coherent with a remarkable nucleation-promoting effect of INT-WS₂ involved in accelerating the cold-crystallization of PLLA. These observations have considerable practical significance for the future sustainable, economic and effective technological utilisation of PLLA, as it will enable the development of novel melt-processable biopolymer nanocomposite materials. Full article

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Polymers, Volume 7, Issue 11 (November 2015) – 18 articles

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