Super‐macroporous dextran cryogels via UV‐induced crosslinking: synthesis and characterization

Cryogenic treatment and UV irradiation were exploited for the preparation of super‐macroporous cryogels from non‐modified high‐molar‐mass dextran. The photo‐crosslinking process was initiated by (4‐benzoylbenzyl)trimethylammonium chloride and N,N′‐methylenebisacrylamide (BAAm) was used as a crosslinking agent. Gel fraction yield and degree of swelling of the dextran cryogels were determined gravimetrically. Cryogel morphology and mechanical properties were studied using environmental scanning electron microscopy and dynamic rheological measurements, respectively. The effects of dextran concentration in the initial polymer solution, polymer molar mass and BAAm content on the crosslinking efficacy, physico‐mechanical properties and morphology of the cryogels were evaluated. The dextran cryogels were assessed as carriers of the model water‐soluble drug metoprolol. © 2017 Society of Chemical Industry     

Effect of aluminum hydroxide on low‐molecular‐weight siloxane distribution and microstructure of high‐temperature vulcanized silicone rubber

This paper investigates the effect of aluminum hydroxide (ATH) content on the free volume and surface recovery property of polydimethylsiloxane (PDMS)–based silicone rubber containing low‐molecular‐weight siloxanes. With increasing ratio of ATH up to 43.1 wt %, the concentration of cyclic siloxanes (D_n = [(CH₃)₂SiO]_n, n = 4–12) in the PDMS matrix increases remarkably, indicative of a spacing effect of ATH particles on the crosslinking of PDMS chains. When more ATH is added, the concentration of D₄–D₁₂ began to decrease. PDMS network variation is verified by free volume size corresponding to τ₃ in positron annihilation lifetime spectroscopy. The o‐Ps intensity decreases linearly with ATH content. Data obtained from X‐ray photoelectron spectroscopy suggest the surface recovery property is weakened by ATH. This process is dominated by the amount of free volume holes in the sample. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45803.     

Degradation of poly(D,L‐lactic acid)‐b‐poly(ethylene glycol)‐b‐poly(D,L‐lactic acid) copolymer by electron beam radiation

This article investigates the effects of electron beam (EB) radiation on poly(D ,L ‐lactic acid)‐b‐poly (ethylene glycol) copolymer (PLA‐b‐PEG‐b‐PLA). The copolymer films were EB irradiated at doses from 0 to 100 kGy. The degradation of these films was studied by measuring the changes in their molecular weight, mechanical and thermal properties. The dominant effect of EB radiation on PLA‐b‐PEG‐b‐PLA is chain‐scission. With increasing irradiation dose, recombination reactions or partial crosslinking may occur in addition to chain scission. The degree of chain scission G_s and crosslinking G_x of sample are calculated to be 0.213 and 0.043, respectively. A linear relationship is also established between the decreases in molecular weight with increasing irradiation dose. Elongation at break of the irradiated sample decreases significantly, whereas its tensile strength decreases slightly. The glass transition temperature (T_g) is basically invariant as a function of irradiation dose. Thermogravimetric analysis shows that its thermal stability decreases with increasing dose. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Role of green tea polyphenol crosslinking in alleviating ultraviolet‐radiation effects on collagen

The widespread application of collagen warrants studies on the effects of ultraviolet (UV) radiation on stabilized collagen. The negative impact of UV radiation is well known. Because collagen is used as a biomaterial in various biomedical applications, knowing the effects of UV irradiation on stabilized collagen has become essential. In this study, the effects of UV irradiation on collagen stabilized with green tea polyphenols, that is, Acacia mearnsii (wattle), and catechin has been studied. The fluorescence intensity has been found to decrease with irradiation for native and wattle‐treated collagen. Spectral studies have indicated that the photodegradation products increase after irradiation for native collagen, whereas collagen treated with catechin or A.mearnsii exhibits different responses depending on the duration of the irradiation. The duration of the irradiation has a significant influence on polyphenol‐treated collagen. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Facile preparation of ODPA‐ODA type polyetherimide‐based carbon membranes by chemical crosslinking

A chemical crosslinking protocol was developed to prepare carbon membranes from 3,3′,4,4′‐oxydiphthalic dianhydride‐4,4′‐oxydianiline (ODPA–ODA) type polyetherimide on the support of phenolic resin sheets. The effects of support pretreatment, membrane‐coating methods and crosslinking protocols on the resultant carbon membranes were investigated. The microstructure, functional group evolution, thermal stability, mechanics, morphology, and gas separation performance of samples were characterized by XRD, FTIR, TGA, mechanical testing technique, and gas permeation technique, respectively. Results have shown that the chemical crosslinking is more beneficial than the popular thermal crosslinking protocol to fabricate supported carbon membranes for the advantage of simple preparation process. In addition, spin‐coating is superior to drop‐coating in terms of good membrane formation on the support. Under the preferred preparation conditions of crosslinker ethylene glycol usage at 10 wt % and spin‐coating, supported carbon membranes can be obtained with good hydrogen separation performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44889.     

Kinetic analysis of the swelling behavior of poly(n‐butylacrylate‐1,6‐hexanedioldiacrylate) networks in 4‐cyano‐4′‐n‐pentyl‐biphenyl (5CB)

The dynamic swelling behavior of chemically crosslinked poly(n‐butylacrylate/1,6‐hexanedioldiacrylate) [poly(Abu‐HDDA)] networks, immersed in an nematogenic and two isotropic solvents, was experimentally analyzed. These networks were elaborated by ultraviolet (UV)–visible light‐induced radical polymerization/crosslinking reactions of Abu/HDDA mixtures, to yield poly(Abu/0.5 wt % HDDA) and poly(Abu/5 wt % HDDA) networks corresponding to weakly and strongly crosslinked systems, respectively. The swelling behavior of these poly(Abu‐HDDA) networks was investigated by immersion in excess solvent, followed by subsequent measurements of the variation of the sample size by means of optical microscopy, depending on temperature and immersion time. Methanol and toluene were employed as isotropic solvents and the nematic liquid crystal molecule 4‐cyano‐4 ′ ‐n‐pentyl‐biphenyl, was considered as anisotropic medium. Swelling ratios were calculated by taking into account diameter sizes as function of immersion time compared to the dry state. Experimental data were analyzed using the Komori–Sakamoto approach and the results of this model were found to be in good agreement with the obtained data. The plateau values of the swelling curves at equilibrium were used to establish phase diagrams as function of temperature and solvent concentration. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45452.     

Photochemistry of 2,6‐di(4′‐azidobenzylidene)‐methylcyclohexanone in polymer matrices

2,6‐Di(4′‐azidobenzylidene)‐methylcyclohexanone (ABC) was one of the most used photoinitiators in negative photoresists industry, rendering insolubility of the resist films at short UV exposure times (several minutes). Although the photodecomposition of aromatic azides is very well established, the peculiarities of the irradiation medium impose specific reaction pathways for arylnitrenes. In this study, photoreactions of arylnitrenes resulted from ABC photolysis were applied in the photoinitiated crosslinking of 1,2‐polybutadiene (1,2‐PB), under soft monochromatic UV irradiation (365 nm). To elucidate the crosslinking mechanism, studies on a model compound were performed. 3‐Methyl‐1‐butene was chosen to simulate the monomeric unit of 1,2‐PB. As a support in photoproducts identifying and with the purpose of a deeper investigation of the ABC photochemistry alone, ABC was photolysed in a rigid matrix of poly(methyl methacrylate). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44694.     

Photochromic properties of color‐matching,double‐shelled microcapsules covalently bonded onto cotton fabric and applications to outdoor clothing

In this research, we aimed to apply color‐matching, double‐shelled microcapsules to deal with outdoor‐clothing sunscreen‐indicator identifications on cotton fabrics with a covalent‐bonding coating method; this method allows one to display both the UV intensity and a warning. The color‐property characteristics of color‐matching‐double‐shelled‐photochromic‐microcapsule–treated patterns on cotton fabrics under various sunshine irradiation intensities are very close to those of inkjet‐printing color‐gradation patterns, which indicate sunshine irradiation intensities. Color‐matching, double‐shelled microcapsules were obtained by the addition of red double‐shelled microcapsules into yellow double‐shelled microcapsules. We increased the weight ratio of the red microcapsules and added blue double‐shelled microcapsules into the red double‐shelled microcapsules when the weight ratio of blue microcapsules was increased. Color‐matching, double‐shelled photochromic microcapsules, whose yellow/red/blue weight ratios were 5.6/0/0, 4.8/0.8/0, 2.4/3.2/0, and 0.8/4.8/0–0/0/5.6, presented distinct color‐property characteristic changes under various irradiation intensities and presented a good color identification; a rather dark, bright color; and good laundering durability of covalent bonding on cotton fabrics. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44698.     

Irradiation dose control for polymer‐matrix composites fabricated by in situ curing with low‐energy electron beam

The electron beam (EB) with emitting energies lower than 150 keV is applicable in in situ curing of polymer‐matrix composites; however, being poor in penetration ability, it leads to significant attenuation of irradiation dose along the prepreg thickness. In this study, polymer‐matrix composites were fabricated by low‐energy EB irradiation curing, and the effect of dose control of double‐sided irradiation was systematically investigated. Experimental results showed that laminates fabricated by single‐sided irradiated prepregs were low in interlaminar shear strength (ILSS) owing to incomplete curing after being post cured at 180 °C for 30 min. A double‐sided irradiation method which included irradiation of equal dose and different doses on both sides of the prepreg was proposed to overcome this difficulty. Analysis showed that under a total dose of 70 and 100 kGy, the ILSS results were high owing to the low curing degree of two adhesive surfaces; under a total dose of 130 and 160 kGy, laminates fabricated with different EB irradiation doses on both sides exhibited enhanced ILSS compared to those with equal dose on both sides, owing to physical adhesion and chemical crosslinking between layers. The ILSS results exhibited the largest increase of 18.9 and 60.5%, respectively, by tuning the dose differences between both sides of the prepregs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44944.     

Plasma surface modification and characterization of collagen‐based artificial cornea for enhanced epithelialization

Argon plasma treatment enhanced the attachment of epithelial cells to a collagen‐based artificial cornea crosslinked using glutaraldehyde (GA) and glutaraldehyde‐polyethylene oxide dialdehyde (GA‐PEODA) systems. The epithelialization of untreated and treated surfaces was evaluated by the seeding and growth of human corneal epithelial cells. Characterization of polymer surface properties such as surface hydrophilicity and roughness was also made by contact angle measurement and atomic force microscopy, respectively. Contact angle analysis revealed that the surface hydrophilicity significantly increased after the treatment. In addition, AFM characterization showed an increase in surface roughness through argon plasma treatment. Based on the biological and surface analysis, argon plasma treatment displays promising potential for biocompatibility enhancement of collagen‐based artificial corneas. It was also found that the cell attachment to artificial cornea surfaces was influenced by the combined effects of surface chemistry (i.e., surface energy), polymer surface morphology (i.e., surface roughness), and polar interactions between functional groups at the polymer surface and cell membrane proteins. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

UV‐Triggered Optical Response and Oxygen Scavenging Ability of a Water‐Soluble Poly(N,N‐dimethylacrylamide‐co‐2‐vinylbenzylanthraquinone) Copolymer

A vinyl‐modified anthraquinone (AQ) derivative (Vinyl‐AQ) is synthesized through a palladium‐mediated Suzuki coupling reaction between vinylphenylboronic acid and 2‐chloromethylanthraquinone and, subsequently, copolymerized with N,N‐dimethylacrylamide (DMAM) through free radical copolymerization in organic solvent. The chemical structure of the resulting water‐soluble copolymer, P(DMAM‐co‐AQ), is verified using techniques such as proton nuclear magnetic resonance, attenuated total reflection‐infrared spectroscopy, thermogravimetric analysis, and UV–vis spectroscopy. The evolution of the oxygen scavenging abilities of aqueous P(DMAM‐co‐AQ) solutions after UV irradiation is monitored as a function of UV irradiation time, concentration of AQ moieties, and pH. The copolymer is proved an effective UV‐triggered oxygen scavenger, leading to dissolved oxygen contents below 1 ppm for the optimized experimental conditions. This behavior is related with the appearance of novel chemical species with interesting optical properties, as suggested by the respective evolution of the UV–vis absorption and photoluminescence spectra after UV irradiation.     

Preparation and property of starch nanoparticles reinforced aldehyde–hydrazide covalently crosslinked PNIPAM hydrogels

Injectable, de‐crosslinkable, and thermosensitive hydrogels are obtained by hydrazide‐functionalized poly(N‐isopropylacrylamide) and aldehyde‐functionalized dextrin through in situ crosslinked method. Natural based and degradable starch nanoparticles (SNPs) are used as fillers in order to improve mechanical property of hydrogels. Internal morphology, dynamic modulus, thermosensitivity property, de‐crosslinking performance, drug release, and in vitro cytotoxicity of hydrogels are investigated. Results show that SNPs disperse well throughout hydrogel and have no significant influence on gelation time and de‐crosslinking performance. Elasticity property of composite hydrogel prepared from 9.0 wt % precursors with 1.5 wt % fillers is improved significantly by SNPs and maximum storage modulus reaches 399.2 kPa, but 89.6 kPa of unreinforced hydrogels. Hydrogels exhibit good thermosensitive performance at alternating cyclic temperature of 25 and 37 °C. Doxorubicin hydrochloride‐loaded hydrogels can release more than 25 days. No significant cytotoxicity to L929 fibroblast cells is observed through a CCK‐8 assay for hydrogels, precursors, and SNPs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45761.     

Antibacterial finishing of polyester/cotton blend fabrics using neem (Azadirachta indica): A natural bioactive agent

The study focused on the development of biofunctional polyester/cotton blend fabric using a natural product. An antimicrobial agent extracted from the seeds of Neem tree (Azadirachta indica) was used for imparting antibacterial property to the blend fabric. Resin and catalyst concentrations were optimized to get the maximum crosslinking in the fabric blends using glyoxal/glycol as a crosslinking agent. The optimized concentrations were used to treat the fabric with the antimicrobial agent along with the crosslinking agent. Quantitative analysis was carried out to measure the antimicrobial activity against Gram‐positive and Gram‐negative bacteria. The results showed that the treated fabrics inhibited the growth of Gram‐positive bacteria (Bacillus subtilis) by more than 90% as compared to the control sample. Antimicrobial activity against Gram‐ positive bacteria was retained up to five machine washes and decreased thereafter. The antibacterial activity was higher against Gram‐positive bacteria as compared to Gram‐ negative bacteria (Proteus vulgaris). The treated fabrics also showed improved crease recovery property although the tensile property showed a marginal decrease. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Elaboration of ion‐exchange membranes with semi‐interpenetrating polymer networks containing poly(vinyl alcohol) as polymer matrix

Ion‐exchange membranes were prepared with semi‐interpenetrating networks (s‐IPNs) by mixing a film‐forming polymer, poly(vinyl alcohol) (PVA), for the crosslinked matrix and a polyelectrolyte for the specific ion‐exchange property. Poly(sodium styrenesulfonate) (PSSNa), poly(styrenesulfonic acid) (PSSH), and poly(acrylic acid) (PAA) were used as anionic polyelectrolytes. Polyethyleneimine (PEI), poly(1,1‐dimethyl‐3,5‐dimethylenepiperidinium chloride) (PDDPCl), and poly(diallyldimethylammonium chloride) (PDDMACl) were used as cationic polyelectrolytes. Membranes with PVA 60% and polyelectrolyte 40% showed the best compromise among mechanical, homogeneous, and ion‐exchange properties. Gaseous dibromoethane was used as a crosslinking agent to form the PVA network and for efficient entrapment of the polyelectrolyte in the membrane. The crosslinking time (tc) was optimized for each type of membrane and its influence was studied by thermogravimetric analysis of the sample and scanning electron microscopy observations. The best results (large ion‐exchange capacity and small swelling ratio) were obtained for PVA/PAA and PVA/PSSNa/PSSH membranes. Among anion‐exchange membranes, PVA/PEI gave the best permselectivity (low co‐ion leakage) and the highest ion‐exchange capacity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1572–1580, 2002; DOI 10.1002/app.10420     

Fabrication of reverse‐osmosis membranes for the desalination of underground water via the γ‐radiation grafting of acrylic acid onto polyethylene films

Research has been devoted to the desalination of saline water to fresh water suitable for human demands because of the shortage of water in some countries. Therefore, in this study, reverse‐osmosis membranes were prepared via the γ‐radiation graft copolymerization of acrylic acid onto high‐density and low‐density polyethylene. The factors that could affect the grafting process, such as the solvent type, monomer and inhibitor concentration, and irradiation dose, were investigated to determine the optimum conditions for radiation grafting. The polyethylene grafted acrylic acid copolymers (PAAc‐g‐PE) graft copolymer was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and mechanical, rheological, and thermal property testing to illustrate the possibility of practical use in water desalination. The prepared grafted membranes showed significant results in the reverse‐osmosis desalination method with underground saline water. The factors affecting the desalination of water, such as the water flux, operation time, and grafting percentage, were studied. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45410.     

Chemically treated hard gelatin capsules for colon‐targeted drug delivery: A novel approach

Hard gelatin capsules, containing riboflavin‐loaded poly (N‐viny1–2‐pyrrolidone)‐polyacrylamide cylindrical hydrogels, were modified chemically by treating with an aqueous formaldehyde solution for the purpose of delayed release of drug along the gastrointestinal tract. The t_dis (disintegration time) of capsules was studied as a function of concentration of formaldehyde solution and the treatment time. The dynamic release of vitamin B₂ was studied as a function of crosslinking ratio of the hydrogels. The device studied seems to have potential to be used for colon‐targeted drug delivery. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2277–2282, 2003     

Crosslinking studies on poly(ethylene terephthalate‐co‐1,4‐phenylene bisacrylate)

Several compositionally different poly(ethylene terephthalate‐co‐1,4‐phenylene bisacrylate) (PETPBA) copolymers were melt spun into fibers. The resulting fibers were subjected to UV irradiation to induce crosslinking. Evidence of crosslinking was obtained from FTIR, solid‐state ¹³C‐NMR, thermal analysis, and solubility. Irradiation of the fiber results in an increased glass‐transition temperature, reduced thermal shrinkage, and enhanced modulus retention at elevated temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1698–1702, 2004     

Temperature‐responsive alginate‐g‐poly(N,N‐diethylacrylamide) copolymer: Synthesis,characterization, and swelling behavior

Temperature‐responsive polymers have recently gained importance due to their applications in drug delivery. Herein, temperature‐responsive graft copolymer (Alg‐g‐PDEAAm) of alginate and N,N‐diethylacrylamide was synthesized by microwave‐assisted copolymerization using potassium persulfate/N,N,N′,N′‐tetramethylethylenediamine initiator system. The reaction conditions for the best grafting (331%) have been optimized by changing microwave irradiation time, temperature, N,N‐diethylacrylamide, and alginate concentrations. The spectroscopic characteristic, thermal properties, and surface morphology of the copolymers were investigated by FTIR, ¹H‐NMR, DSC/TGA, XRD, gel permeation chromatography, and SEM. Furthermore, low critical solution temperatures of Alg‐g‐PDEAAm copolymers were detected by UV spectroscopy. Swelling ratio of graft microspheres was carried out at 25, 32, and 37 °C, and microspheres were found exhibiting temperature‐responsive property. Cytotoxicity test indicated the Alg‐g‐PDEAAm copolymer and its microsphere were biocompatible. Therefore, based on the results the synthesized temperature‐responsive copolymer could be considered as a promising biomaterial. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46688.     

Evidence of irradiation‐induced crosslinking in miscible blends of poly(vinyl chloride)/epoxidized natural rubber in presence of trimethylolpropane triacrylate

Electron‐beam initiated crosslinking of a poly(vinyl chloride)/epoxidized natural rubber blend (PVC/ENR), which contained trimethylolpropane triacrylate (TMPTA), was carried out over a range of irradiation doses (20–200 kGy) and concentrations of TMPTA (1–5 phr). The gelation dose was determined by a method proposed by Charlesby. It was evident from the gelation dose, resilience, hysteresis, glass‐transition temperature (T_g), IR spectroscopy, and scanning electron microscopy studies that the miscible PVC/ENR blend underwent crosslinking by electron‐beam irradiation. The acceleration of crosslinking by the TMPTA was further confirmed in this study. Agreement of the results with a theory relating the T_g with the distance between crosslinks provided further evidence of irradiation‐induced crosslinking. The possible mechanism of crosslinking induced by the irradiation between PVC and ENR is also proposed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1914–1925, 2001     

Removal of textile dyes from single and ternary solutions using poly(acrylamide‐co‐N‐methylacrylamide) grafted katira gum hydrogel

A novel hydrogel poly(acrylamide‐co‐poly‐N‐methylacrylamide) grafted katira gum (KG) was synthesized via free radical copolymerization using a mixture of acrylamide and N‐methylacrylamide in presence of N,N′‐methylene‐bis‐acrylamide as a crosslinking agent. A series of hydrogels (KG‐1 to KG‐6) were prepared by varying amount of acrylamide and N‐methylacryamide. Poly‐acrylamide‐g‐katira gum (PAM‐g‐KG) and poly‐N‐methylacrylamide‐g‐katira gum (PNMA‐g‐KG) hydrogels were also prepared using same crosslinking agent. Swelling characteristics of all the prepared hydrogels in water were evaluated and the hydrogel with best swelling property (KG‐6) was identified. The hydrogel KG‐6 was characterized by FTIR, X‐ray diffractometer, and scanning electron microscopy and was used for the adsorption of textile dyes namely methylene blue (MB), malachite green (MG), and congo red (CR) from single and ternary solutions. Adsorption dynamics, kinetics, isotherm, and thermodynamics of all the prepared hydrogels were studied in the ternary dye solutions. The sorption kinetics data were fitted well to pseudo‐second order and the equilibrium adsorption data were found to follow Freundlich isotherm model. The thermodynamics studies showed that the adsorption process was spontaneous and exothermic in nature. The preferential dye adsorption by the hydrogel was followed in the order MB > MG > CR. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45958.