bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer hybrids from self‐emulsified PU anionomer and water‐reducible acrylate copolymer via a postcuring reaction
Authors: Lai Jian‐Zei , Ling Hao‐Jan , Chen Guan‐Nan , Yeh Jen‐Taut , Chen Kan‐Nan 
Published: October 2003

AbstractWater‐reducible acrylate copolymer is obtained from a free‐radical copolymerization of n‐butyl acrylate, acrylic acid, and methacrylic acid. Self‐emulsified aqueous‐based polyurethane (PU) anionomer is prepared by the conventional method. The latent curing agents (di‐ and triaziridinyl compounds, HDDA‐AZ and TMPTA‐AZ) are synthesized from the reaction of aziridine with hexandiol diacrylate and trimethylolpropane triacrylate, respectively. These two polymers and the latent curing agent are miscible in each other and become a single component and self‐curable polymer dispersion. The carboxyl ions of polymers not only stabilize the aqueous polymer dispersions but also serve the curing site toward latent curing agent in the drying process. These two polymers blend with a curing agent, which results in new polymer hybrid formation. These polymer hybrids have the improvements on performance properties and the cost/performance benefits. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3578–3587, 2003
Effect of degree of deacetylation of chitosan on the kinetics of ultrasonic degradation of chitosan
Authors: Tsaih Min Larng , Chen Rong Huei 
Published: October 2003

AbstractThe objective of the study was to explore the effect of the degree of deacetylation (DD) of the chitosan used on the degradation rate and rate constant during ultrasonic degradation. Chitin was extracted from red shrimp process waste. Four different DD chitosans were prepared from chitin by alkali deacetylation. Those chitosans were degraded by ultrasonic radiation to different molecular weights. Changes of the molecular weight were determined by light scattering, and data of molecular weight changes were used to calculate the degradation rate and rate constant. The results were as follows: The molecular weight of chitosans decreased with an increasing ultrasonication time. The curves of the molecular weight versus the ultrasonication time were broken at 1‐h treatment. The degradation rate and rate constant of sonolysis decreased with an increasing ultrasonication time. This may be because the chances of being attacked by the cavitation energy increased with an increasing molecular weight species and may be because smaller molecular weight species have shorter relaxation times and, thus, can alleviate the sonication stress easier. However, the degradation rate and rate constant of sonolysis increased with an increasing DD of the chitosan used. This may be because the flexibilitier molecules of higher DD chitosans are more susceptible to the shear force of elongation flow generated by the cavitation field or due to the bond energy difference of acetamido and β‐1,4‐glucoside linkage or hydrogen bonds. Breakage of the β‐1,4‐glucoside linkage will result in lower molecular weight and an increasing reaction rate and rate constant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3526–3531, 2003
Synthesis and characterization of temperature‐ and pH‐sensitive poly(N,N‐diethylacrylamide‐co‐methacrylic acid)
Authors: Liu Shouxin , Liu Mingzhu 
Published: October 2003

AbstractA series of pH‐ and temperature‐responsive (N,N‐diethylacrylamide‐co‐methacrylic acid) (DEAM–MAA) random copolymers were synthesized by free‐radical copolymerization techniques, and their lower critical solution temperatures (LCSTs) at different pH values and their critical phase‐transition pH values at different temperatures were determined by transmittance measurements, respectively. The LCSTs of DEAM–MAA copolymers depend on the MAA content in the copolymers and are significantly affected by the pH of the aqueous solution. Similarly, the critical phase‐transition pH values also depend on the MAA content of the DEAM–MAA copolymers and are significantly affected by the temperature of the aqueous solution. The LCST of DEAM–MAA copolymers increases with an increase in the MAA content. The critical phase‐transition pH increases with increasing MAA content in the copolymer and also increases with increasing aqueous solution temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3563–3568, 2003
Feasibility of conducting semi‐interpenetrating networks based on a poly(ethylene oxide) network and poly(3,4‐ethylenedioxythiophene) in actuator design
Authors: Vidal F. , Popp J.‐F. , Plesse C. , Chevrot C. , Teyssié D. 
Published: October 2003

AbstractA new type of synthetic pathway—the use of interpenetrating polymer networks (IPNs)—is proposed to design conducting polymer‐based actuators. Two types of materials with interesting conducting properties were prepared: (1) a semi‐IPN between poly(3,4‐ethylenedioxythiophene) (PEDOT) and branched poly(ethylene oxide) (PEO) network; (2) a tricomponent IPN between PEDOT and a PEO/polycarbonate (PC)–based network as the ionic conducting partner. In the first case, the influence of the amount of branching in the PEO network on the EDOT uptake and electrochemical properties was studied. A maximum conductivity (15 S cm−1) was obtained for 60 wt % branched PEO in the material. Moreover, the dispersion profile of PEDOT in the material was shown by elemental analysis and energy dispersion spectroscopy to follow a gradient through the thickness of the film leading to a built‐in three‐layered device. With respect to PEO/PC materials, the best results were obtained for about 80 wt % PEO in the matrix where the material remains sufficiently elastomeric. In this case, the conductivity reaches about 1 S cm−1 for a 10 to 30 wt % polycarbonate content. These materials are capable of reversible 45° angular deflections under a 0.5V potential difference. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3569–3577, 2003
Rheological and mechanical properties of natural rubber reinforced with agricultural byproduct
Authors: Imanah J. E. , Okieimen F. E. 
Published: October 2003

AbstractCocoa pod powdered (CP) and Carbonized Cocoa pod powdered (CCP) sieved through 150 μm mesh were characterized in terms of loss on ignition, surface area, moisture content, and oil absorption and used as filler in compounding natural rubber and vulcanized using efficient vulcanization system. The processing and curing characteristics of the compound mixes were determined on a Monsanto Rheometer. Physical‐mechanical properties of the vulcanizates were measured as a function of filler loading. It was found that vulcanizates with 40–50% filler loading showed maximum tensile strength of 8.4 MPa for CP, and 9.5 MPa for CCP. Hardness showed increased with increased filler loading for all the compounds. The reinforcing ability of the cocoa pod husk is not much inferior when compared to Carbon Black, N330. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3718–3722, 2003
Synthesis of poly(p‐diphenylmethylterephthalamide) from recycled monomers
Authors: Norakankorn C. , Chuayjuljit S. , Pimpan V. 
Published: October 2003

AbstractPoly(p‐diphenylmethylterephthalamide) or PMA was synthesized from the reaction between recycled terephthalic acid (TPA) and recycled 4,4′‐methylenedianiline (MDA) in the presence of pyridine, triphenyl phosphite, and a solubilizing‐aid agent. The reaction conditions used for this polymerization were determined from a model reaction using pure TPA and pure MDA as reactants. It was found that PMA with the highest % yield and molecular weight was obtained when the mixture of lithium chloride (LiCl) and calcium chloride (CaCl2) were used as solubilizing‐aid agents with a reaction time of 4 h. Recycled TPA with 92% purity was obtained from acid hydrolysis of waste PET bottles using sulfuric acid as a catalyst at 150°C for 5 h. Recycled MDA with 99% purity was obtained from aminolysis of rigid polyurethane foam scrap using diethylenetriamine as a degrading agent at 180°C for 70 min. PMAs prepared from recycled monomers exhibited thermal properties, which were comparable to those of PMA prepared from pure monomers. However, due to a possibility of several isomers present in recycled MDA, PMAs prepared from this monomer had lower melting points and thermal decomposition temperatures than those prepared from pure MDA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3723–3729, 2003
Recycling of jute textile in phenol formaldehyde–jute composites
Authors: Hassan Mohammad L. 
Published: October 2003

AbstractJute textile was recycled into composites using different percents of phenol formaldehyde (PF) resin. The effect of the resin percent, from 12 to 30%, on the flexural strength, tensile strength, water absorption, and thickness swelling of the produced composites was studied. To improve the dimensional stability of the produced composites, jute textile was acetylated or steamed. The effect of steaming and acetylation on the structure and thermal stability of jute fibers was studied using Fourier Transform Infrared (FTIR) spectroscopy and Thermogravimetric analysis (TGA), respectively. The effect of these treatments on the flexural strength, tensile strength, water absorption, and thickness swelling of the produced composites was studied. Steaming of jute textile was superior to acetylation in improving the dimensional stability. Cyclic wetting and drying test of the composites showed that steaming of the jute textile resulted in much less irreversible and reversible thickness swelling than in case of using acetylated or untreated jute textile. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3588–3593, 2003
Polystyrene‐supported polyoxyethylene bound potassium permanganate as a heterogeneous oxidizing agent
Authors: Chacko Asha , Mathew Beena 
Published: October 2003

AbstractOxidation behavior of a 2 mol % divinylbenzene (DVB)‐crosslinked polystyrene‐supported permanganate function was investigated toward low molecular weight primary and secondary alcohols and aldehydes. The permanganate function was attached to a polystyrene support through cyclic polyoxyethylene (POE) units immobilized on the support. Contrary to the oxidations catalyzed by low molecular weight permanganate reagents, the oxidation of primary alcohol terminated in the aldehyde stage. The secondary alcohols were converted to the respective ketone and aldehyde to acid. The effect of the variable parameters similar to solvent, temperature, and reagent to substrate ratio was followed. Nonpolar cyclohexane was found to be the best solvent for the present study. Also the reactivity increased with increasing temperature. The oxidizing reagent possesses a long shelf life and could be recycled several times without reduction of capacity and mechanical stability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3708–3717, 2003
Study on propene polymerization using a novel spherical Ziegler‐Natta catalyst and its kinetics
Authors: Ye Zhao‐Yang , Wang Li , Jiang Shan 
Published: October 2003

AbstractThe effects of the Al/Ti ratio and external donor (ED) on the catalytic activity and kinetics of propene polymerization catalyzed by a spherical Ziegler‐Natta (Z‐N) catalyst were investigated. The preparation conditions of the catalyst play an important role in the polymerization kinetics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3737–3740, 2003
Effect of aluminum chloride and Pt/ TiO2 on the thermal degradation of poly(vinyl chloride) in solution
Authors: Gupte Sachin L. , Agarwal Nitin , Madras Giridhar , Nagaveni K. , Hegde M.S. 
Published: October 2003

AbstractThe effect of two catalysts, Pt/TiO2 and aluminum chloride, on the degradation of poly (vinyl chloride) (PVC) in solution was investigated at various temperatures. The molecular weight distribution of the polymer was obtained by analyzing the samples by gel permeation chromatography. Experimental data indicated that the catalysts enhanced the degradation rate of PVC compared to the thermal degradation of PVC. Continuous distribution kinetic models were used to evaluate the degradation rate coefficients. The activation energy, calculated from the temperature dependence of rate coefficients, was 26.5, 31.5, and 43.7 kcal/mol for the thermal degradation of PVC in solution, in the presence of Pt/TiO2 and in the presence of AlCl3, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3532–3535, 2003
Preparation and swelling behavior of biodegradable hydrogels based on α,β‐poly(N‐2‐hydroxyethyl‐DL‐aspartamide)
Authors: Yoon Seung‐Wook , Chung Dong Jun , Kim Ji‐Heung 
Published: October 2003

AbstractBiodegradable polymers and the hydrogels have been increasingly applied in a variety of biomedical fields and pharmaceutics. α,β‐Poly(N‐2‐hydroxyethyl‐DL‐aspartamide), PHEA, one of poly(amino acid)s with hydroxyethyl pendants, are known to be biodegradable and biocompatible, and has been studied as an useful biomaterial, especially for drug delivery, via appropriate structural modification. In this work, hydrogels based on PHEA were prepared by two‐step reaction, that is, the crosslinking of polysuccinimide, the precursor polymer, with oligomeric PEG or PEI‐diamines and the following nucleophilic ring‐opening reaction by ethanolamine. Soft hydrogels possessing varying degrees of gel strength could be prepared easily, depending on the amount of different crosslinking reagents. The swelling degrees, which were in the range of 10–40 g–water/dry gel, increased somewhat at higher temperature, and also at alkaline pH of aqueous solution. A typical hydrogel remained almost unchanged for 1 week, at 37°C in phosphate buffer of pH 7.4, and then seemed to degrade slowly as time. A porous scaffold could be fabricated by the freeze drying of water‐swollen gel. The PHEA‐based hydrogels have potential for useful biomaterial applications including current drug delivery system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3741–3746, 2003
Dielectric properties of aluminum–epoxy composites
Authors: Singh Vishal , Kulkarni A. R. , Rama Mohan T. R. 
Published: October 2003

AbstractDielectric properties of Al–epoxy composites were characterized as a function of composition, frequency, and temperature. The dielectric constant increased smoothly with an increase in the concentration of aluminum. An increase in dielectric constant was also observed with an increase in temperature as well as with a decrease in frequency. In general, dissipation factor values for composites with higher concentrations of aluminum were greater than those with lower volume content of aluminum. Also, the dissipation factor showed an increase both with a decrease in frequency and an increase in temperature. The increase in values of dielectric constant and dissipation factor with an increase in concentration of aluminum was attributed to interfacial polarization. The absence of any discontinuity in the plot of dielectric constant versus composition was ascribed to the absence of continuous aluminum chains in the composition range investigated. The increase in dielectric constant with a rise in temperature was attributed to the segmental mobility of the polymer molecules. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3602–3608, 2003
Study on antistatic modification of polyurethane elastomer surfaces by grafting with vinyl acetate and antistatic agent
Authors: Zhou Xiangdong , Liu Pengsheng 
Published: October 2003

AbstractUnder UV light, vinyl acetate (VAc) was grafted onto polyurethane (PU) elastomer membrane, using benzoyl peroxide as photoinitiator. After surface alcoholysis reaction, hydroscopic hydroxyl formed on the surface of PU, and under catalysis of MgCl2, the antistatic agent combined with hydroxyl by chemical linkage, so that the antistatic durability of PU improved. The ATR‐FTIR spectrum, X‐ray photoelectron spectroscopy, and SEM characterized the grafted copolymers and verified the occurrence of grafting copolymerization. The effect of grafting degree of VAc on the antistatic ability of PU surface was also investigated in this study. Experimental results showed that after modification the surface electric resistivity of PU elastomer reached the nearly 108Ω class, with little change in spite of a washing‐fastness experiment, although its mechanical ability was slightly decreased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3617–3624, 2003
Nanosize polymer latices made by microemulsion copolymerization: Preparation and characterization
Authors: Zhang Yuying , Guo Tianying , Hao Guangjie , Song Maodao , Zhang Banghua 
Published: October 2003

AbstractPolymer nanoparticles were prepared by a methyl methacrylate/butyl methacrylate/2‐hydroxyethyl methacrylate/acrylate or methyl acrylate microemulsion copolymerization process. A microemulsion copolymerization method was used. With this process high polymer : surfactant weight ratios (≥15 : 1), relatively concentrated (∼ 30 wt %) lattices, and small (∼ 60 nm) particle diameters were obtained. Properties of the latices were characterized in detail by TEM, DSC, dynamic light scattering, spectrophotometry, and tensile strength testing. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3625–3630, 2003
Behavior of poly(methyl methacrylate)–based systems in supercritical CO2 and CO2 plus cosolvent: Solubility measurements and process assessment
Authors: Domingo C. , Vega A. , Fanovich M. A. , Elvira C. , Subra P. 
Published: October 2003

AbstractMicrospheres based on synthetic polymers such as poly(methyl methacrylate) (PMMA) and PMMA blends are known for their medical and optical applications. The development of methods for processing polymeric microspheres using a nontoxic solvent, like supercritical carbon dioxide (SCCO2), is desirable. This work investigates the solubility and behavior of polymers (PMMA and PMMA/polycaprolactone blend) and solutes (cholesterol and albumin) in SCCO2 and SCCO2 + cosolvent (acetone, ethanol, and methylene chloride). The knowledge of solubility behavior of materials in SCCO2 aids in the selection and/or design of the most appropriate technique for materials processing. Processing PMMA‐based polymers with pure SCCO2 leads to polymer swelling. The lack of polymer solubility in pure CO2 precludes their micronization by the RESS (rapid expansion of supercritical solutions) process, but on the other hand allows their impregnation. Polymer plasticization caused by CO2 can be exploited in the PGSS (particles from gas‐saturated solutions) process. Addition of a liquid cosolvent to CO2 enhances the dissolution of solutes and polymers. Precipitation of the studied polymers by antisolvent techniques seems feasible only by use of CO2 + methylene chloride. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3652–3659, 2003
Chemical modification of keratin fibers using 2‐iminothiorane hydrochloride
Authors: Kuzuhara A. 
Published: October 2003

AbstractFor the purpose of improving the properties of keratin fibers by chemical modification, we attempted to introduce new disulfide (–SS–) groups into hair using 2‐iminothiorane hydrochloride (2‐IT). After the evaluation of the setting ability of human hair, the waving permanence (66%) of our proposed permanent hair‐setting process clearly improved compared with that of a conventional permanent hair‐setting process (48%). Next, it became clear that new –SS– groups were created in the human hair samples as a result of introducing and then oxidizing new –SH groups. This –SS– content in the hair samples was estimated by employing FT‐Raman spectroscopy. By examining the Raman bands of the treated and untreated hair, it was seen that each band of treated hair did not change, except for the increase of the –SS– groups. This suggests that hair damage does not occur as a result of the investigated treatment. From these experiments, the chemical modification of keratin fibers using 2‐IT was clearly effective for a permanent hair‐setting process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3646–3651, 2003
Preparation of poly(acrylic acid)–chitosan hydrogels by gamma irradiation and in vitro drug release
Authors: Shim Jae‐Woon , Nho Young‐Chang 
Published: October 2003

AbstractBiocompatible and biodegradable pH‐responsive hydrogels based on poly(acrylic acid) (AAc) and chitosan were prepared for controlled drug delivery. These interpolymeric hydrogels were synthesized by a gamma irradiation polymerization technique. The degree of gelation was over 96% and increased as the chitosan or acrylic acid content increased. The equilibrium swelling studies of hydrogels prepared in various conditions were carried out in an aqueous solution, and the pH sensitivity in the range of pH 1–12 was investigated. The AAc/chitosan hydrogels showed the highest water content when the 30 vol % AAc and 0.1 wt % chitosan were irradiated with a 30‐kGy radiation dose. Also, an increase of swelling degree with an increase in the pH was noticed and showed the highest value at pH 12. The drug, 5‐fluorouracil, was loaded into these hydrogels and the release studies were carried out in simulated gastric and intestinal fluids. The in vitro release profiles of the drugs showed that more than 90% of the loaded drugs were released in the first 1 h at the intestinal pH and the rest of the drug had been released slowly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3660–3667, 2003
Intercalary heterochromatin and genetic silencing
Authors: Zhimulev Igor F. , Belyaeva Elena S. 
Published: October 2003

AbstractWe focus here on the intercalary heterochromatin (IH) of Drosophila melanogaster and, in particular, its molecular properties. In the polytene chromosomes of Drosophila, IH is represented by a reproducible set of dense bands scattered along the euchromatic arms. IH contains mainly unique DNA sequences, and shares certain features with other heterochromatin types such as pericentric, telomeric, and PEV‐induced heterochromatin, the inactive mammalian X‐chromosome and the heterochromatized male chromosome set in coccids. These features are transcriptional silencing, chromatin compactness, late DNA replication, underrreplication or elimination in somatic cells, and formation of the heterochromatin state in early embryogenesis. Post‐translational modification of histones and the specific nonhistone protein complexes are shown to participate in the establishment and maintenance of silencing for all heterochromatin types. Many IH regions contain binding sites for HP1 and/or Pc‐G proteins and all the regions are sites of heterochromatin‐associated SuUR protein. Some IH regions are known to contain homeotic genes. Summarizing these data, we suggest that IH regions comprise stable inactivated genes, whose silencing is developmentally programmed. BioEssays 25:1040–1051, 2003. © 2003 Wiley Periodicals, Inc.
DNMT cooperativity—the developing links between methylation, chromatin structure and cancer
Authors: El‐Osta Assam 
Published: October 2003

AbstractControversy has reigned for some time over the biological connection between DNA methylation and cancer. For this reason, the methylation mechanism responsible for increased cancer risk has received greater attention in recent years. Tumor suppressor genes are often hypermethylated resulting in gene silencing. Although some have questioned this interpretation of the link between methylation and cancer, it appears that both hypermethylation and hypomethylation events can create epigenetic changes that can contribute to cancer development. Recent studies have shown that the methyltransferases DNMT1 and DNMT3b cooperatively maintain DNA methylation and gene silencing in human cancer cells. Disruption of the human DNMT3b only slightly reduces the overall global DNA methylation; however, demethylation was markedly potentiated when both DNMT1 and DNMT3b were simultaneously deleted. The results to these experiments provide compelling evidence towards a role for DNA methylation in cancer. This review discusses the current understanding of cancer‐epigenetic information and highlights recent studies that connect the methylation machinery and chromatin remodelling with cancer susceptibility. BioEssays 25:1071–1084, 2003. © 2003 Wiley Periodicals, Inc.