bluuebunny/crossref_metadata_2025_split huggingface dataset:
Butyltins and calmodulin: which interaction?
Authors: Cima Francesca , Dominici Debora , Mammi Stefano , Ballarin Loriano 
Published: August 2002

AbstractTributyltin (TBT), widely used as an antifouling biocide, is the most abundant pesticide in coastal environments. One of its main toxic effects is immunosuppression in both vertebrates and invertebrates. At sublethal doses of TBT, phagocytes lose their ability to move towards and ingest foreign particles. For short‐term cultures of haemocytes (60 min at 25 °C) of a marine invertebrate, the colonial ascidian Botryllus schlosseri, exposed to 10−5 M TBT, we previously reported dose‐ and time‐dependent impairment of yeast phagocytosis and changes in cell morphology related to cytoskeleton disorganization. These effects are Ca2+‐dependent, since inactivation of Ca2+‐adenosine triphosphatase and a sustained increase in cytosolic Ca2+ occurred. As TBT can antagonize the effect of chlorpromazine, a specific calmodulin (CaM) inhibitor, and the co‐presence of exogenous CaM and TBT in the incubation medium resulted in the absence of effects, we hypothesized an interaction between TBT and CaM. TBT may remove endogenous CaM from cell proteins, thus inactivating them and causing alteration of Ca2+ homeostasis. With the aim of confirming the hypothesis of a direct TBT–CaM interaction, we first studied the effects of co‐incubation of TBT with other exogenous proteins on restoring the ability of phagocyte morphology. Although bovine serum albumin was never able to restore cell morphology, the effect of human spectrin was similar to that described for CaM, suggesting a common non‐specific mechanism of action based on the interaction of TBT with exposed hydrophobic pouches. We also analysed the conformational changes of pure CaM (10−5 M) in the presence of various concentrations (10−4 to 10−3 M) of TBT and its degradation products, dibutyltin (DBT) and monobutyltin (MBT), by circular dichroism. Results indicate the dose‐ and time‐dependent interaction of TBT with CaM. This interaction is a non‐covalent interaction, probably hydrophobic in nature, between the aliphatic chains of TBT and the hydrophobic regions of Ca2+‐activated CaM. DBT and MBT turned out to be less active in inducing CaM conformational changes, without any significant differences between the two compounds. Copyright © 2002 John Wiley & Sons, Ltd.
Swelling kinetics of poly(N‐vinylimidazole‐co‐sodium styrenesulfonate) hydrogels
Authors: Valencia Joaquín , Piérola Inés F. 
Published: August 2002

AbstractHydrogels of N‐vinylimidazole and sodium styrenesulfonate were synthesized by radical crosslinking copolymerization. Transient swelling measurements in water, at room temperature, reveal an unusual behavior. For some gel compositions, the swelling time dependency is about a δ function: dry hydrogel pellets swell up readily to reach a high degree of swelling and, spontaneously, they deswell to collapse. Such peculiarity was interpreted in terms of several competing events in the swelling mechanism: water diffusion toward the gel, chain disentanglement, sodium–proton interchange through the gel–external bath boundary, approaching of chains to allow interaction of sulfonate groups with neighboring protonated imidazole moieties and diffusion of water outside the gel. The results of cyclic swelling–deswelling following abrupt changes of composition in the external bath, from water to sodium hydroxide solution, support that mechanism. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 191–200, 2002
Suppression of radiation‐induced oxidation of polymers by sputtered silicon oxide coating
Authors: Zheng W. , Kobayashi Y. , Hirata K. , Miura T. , Kobayashi T. , Iwaki M. , Oka T. , Hama Y. 
Published: August 2002

AbstractOxygen barrier coating on polymers was attempted to obtain polymeric composite materials with improved radiation resistance. Silicon oxide (SiO1.6) films ranging from 120 to 240 nm thick were formed on polypropylene (PP) and polyethylene (PE) by radio frequency (RF) magnetron sputtering. Oxygen permeability after SiO1.6 deposition was reduced significantly in all samples studied, indicating that silicon oxide is a useful gas barrier. The oxygen permeability coefficient of deposited films for PP was 1.7–2.2 × 10−14 cm3‐cm/cm2/s/cmHg and that for PE was 2.8–4.8 × 10−13 cm3‐cm/cm2/s/cmHg. We studied the effect of such films on the radiation resistance of polymers in the presence of oxygen by microscopic infrared (IR) absorption spectroscopy. Silicon oxide films 180 nm thick were deposited on the surfaces of PP and PE, and the formation of carbonyl groups after irradiation in air was measured as a function of depth from the surface. Results compared with those for uncoated PE and PP showed that the radiation‐induced polymer oxidation is dramatically suppressed by silicon oxide coating. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 186–190, 2002
Isothermal crystallization behavior and properties of polypropylene/EPR blends nucleated with sodium benzoate
Authors: Jang Gu‐Su , Jo Nam‐Ju , Cho Won‐Jei , Ha Chang‐Sik 
Published: August 2002

AbstractThe effect of sodium benzoate on the isothermal crystallization behavior of isotactic polypropylene (iPP)/ethylene–propylene rubber(EPR) blends was investigated using differential scanning calorimetry. Dynamic mechanical and physical properties of the iPP/EPR blends nucleated with sodium benzoate were also measured. It was found that the crystallization behavior and physical properties such as heat deflection temperature (HDT), flexural modulus, and impact strength were strongly affected by the competition between the nucleating effect of EPR attributed to its partial compatibility with iPP and the simple addition of the amorphous component, as well as the nucleating effect of sodium benzoate. High impact strength was achieved by addition of EPR and sodium benzoate to iPP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 201–211, 2002
Compatibilization of intumescent flame retardant/polypropylene composites based on α‐methacrylic acid grafted polypropylene
Authors: Ma Zhi‐Ling , Zhao Min , Hu Han‐Fang , Ding Hai‐Tao , Zhang Jie 
Published: August 2002

AbstractA phosphoric acid–pentaerythritol–melamine copolymer was selected as an intumescent flame retardant (IFR). The influence of α‐methacrylic acid grafted polypropylene (PP‐g‐MAA) on the properties and compatibility of IFR/PP composites was studied. The results obtained from mechanical tests and scanning electron microscopy showed that PP‐g‐MAA was a true coupling agent for IFR/PP blends, but it did not change the necessary flame retardancy. The cocrystallization between bulk PP and PP segments of PP‐g‐MAA was proved by wide‐angle X‐ray diffraction analysis. A flow test showed that the flow behaviors of composites in the melt were those of a pseudoplastic liquid and it was very small for PP‐g‐MAA and affected the rheological behavior of the PP/IFR composite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3128–3132, 2002; DOI 10.1002/app.10099
A novel visible light photo‐induced acid‐generation system
Authors: Huimin Wang , Yongcai Jiang , Qingshan Li , Xiaohong Zhang , Shikang Wu 
Published: August 2002

AbstractA novel, visible light, photo‐induced acid‐generation system composed of four types of intramolecular charge transfer compound and substituted bis(trichloromethyl) triazine was studied in this work. The photo‐induced electron transfer process between electron donor and electron acceptor was studied by the methods of fluorescence quenching and the change of fluorescence intensity with the time of irradiation. In the acidity measurement, the chemical reaction of acid formation of the studied system can be observed clearly. The acid‐induced cross‐linking reaction of m‐cresol resin and 2,4,6‐tris‐[N,N‐di(methoxymethyl) amino] triazine (HMMM) has also been studied. A clear negative image can be obtained after irradiation and developing by solvent. The possible mechanism of reaction has been discussed before. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 909–915, 2002; DOI 10.1002/app.10103
Water‐soluble grafted polysaccharides containing sulfobetaine groups: Synthesis and characterization of graft copolymers of hydroxyethyl cellulose with 3‐dimethyl(methacryloyloxyethyl)ammonium propane sulfonate
Authors: Zhang Li‐Ming , Chen Li‐Qiong 
Published: August 2002

AbstractNew water‐soluble grafted polysaccharides containing sulfobetaine groups were synthesized by the grafting of the sulfobetaine‐type zwitterionic monomer 3‐dimethyl‐(methacryloyloxyethyl)ammonium propane sulfonate (DMAPS) onto hydroxyethyl cellulose (HEC) in the presence of a ceric ammonium nitrate (CAN)/ethylenediaminetetraacetic acid (EDTA) initiation system. The effects of the concentrations of CAN, EDTA, DMAPS, and HEC, as well as the polymerization time and temperature, on the grafting reactions were investigated in terms of the grafting percentage (%GP) and grafting conversion (%GC) of the monomer. The %GP and %GC increased and then decreased with increasing concentrations of CAN, EDTA, and HEC. The %GP and %GC increased with increasing DMAPS concentration up to a certain value, beyond which the %GP did not significantly increase and the %GC decreased. The appropriate polymerization time and temperature were favorable for the grafting reactions. With infrared, thermogravimetric analysis, and viscosity measurements, the resulting grafted polysaccharides were characterized. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2755–2761, 2002; DOI 10.1002/app.10191
Semifluorinated ABA triblock copolymers: Synthesis, characterization, and amphiphilic properties
Authors: Zhang Zhao Bin , Ying Sheng Kang , Hu Qing Hua , Xu Xu Dong 
Published: August 2002

AbstractIn this study a series of novel semifluorinated ABA triblock copolymers with different fluorinated segment lengths and different fluorocarbon side‐chain structures were synthesized via atom transfer radical polymerization (ATRP) and macroinitiator techniques. The macroinitiator, telechelic bromine terminated polystyrene, was obtained from bulk ATRP of styrene with α,α′‐dibromo‐p‐xylene as the initiator and cuprous bromide/α,α′‐bispyridine complex as the catalyst. The polymerization reactions of 2‐[(perfluorononenyl)oxy] ethyl methacrylate and ethylene glycol monomethacrylate monoperfluorooctanoate were initiated by the macroinitiator in the presence of additional catalyst. The characterization of the block copolymers was performed by gel permeation chromatography, 1H‐NMR spectroscopy, and differential scanning calorimetry. The surface activities of the block copolymers in toluene were investigated with the Wilhelmy plate method. The solid surface energy of the block copolymers was determined by measurement of the contact angles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2625–2633, 2002
Investigations of surface degradation of high‐density polyethylene materials resulting from tracking, using physicochemical analysis
Authors: Sarathi R. 
Published: August 2002

AbstractIn the present work tracking phenomena were studied with high‐density polyethylene (HDPE) materials under dc voltage, with NH4Cl and acid rain as contaminants. It was determined that the tracking time of the material depends on the conductivity and flow rate of the contaminant. Furthermore, physicochemical analysis by wide‐angle X‐ray diffraction studies, differential scanning calorimetry, and luminescence spectroscopy was carried out, whereupon it was concluded that the tracking process is a surface‐degradation process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2843–2849, 2002; DOI 10.1002/app.10260
Studies of novel monomeric and polymeric azo disperse dyes
Authors: Maradiya Hari R. , Patel Vithal S. 
Published: August 2002

AbstractA series of polymeric dyes were synthesized by free‐radical addition polymerization of monomeric dyes that were derived from diazotized 2‐amino‐3,5‐bis‐(ethoxycarbonyl)‐4‐methylthiophene by coupling with various N‐arylmaleimides. All the polymeric dyes were characterized by elemental analysis, IR and visible spectroscopy, viscometry, and TGA. Color and dyeability of the polymeric dyes are discussed by comparing them with those of the corresponding monomeric dyes. All the dyes have been found to give various color shades with good to very good depth and levelness on the fiber. The dyeing of the monomeric dyes shows good fastness to light and very good to excellent fastness to washing, perspiration, sublimation, and solvents. The corresponding polymeric dyes show excellent fastness properties. The percentage dyebath exhaustion and fixation on the fiber have been found to be good to very good (60–90%). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1380–1389, 2002; DOI 10.1002/app.10276
Synthesis and properties of PVC‐bound N,N‐dialkylaminopyridine
Authors: Wei Rongbao , Liang Ya , Chen Suzhan , Jia Chenxi , Li Fan , Zhang Tao 
Published: August 2002

AbstractA linear poly(vinyl chloride) (PVC)‐supported dialkylaminopyridine was prepared through PVC treated with N‐methylaminopyridine and NaH in tetrahydrofuran. The properties of this PVC‐bound catalyst were examined by acetylation of linalool and 5‐FU. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1067–1069, 2002; DOI 10.1002/app.10391
Functionalization of crosslinked polyacrylamide through γ‐radiation‐induced grafting of 4‐vinylpyridine
Authors: Pande C. S. , Sharma Ajay 
Published: August 2002

AbstractCrosslinked polyacrylamide beads were irradiated in air with a Co60 γ‐radiation source. The preirradiated beads were graft‐copolymerized through heating with 4‐vinylpyridine in the presence of benzoyl peroxide. Grafting was studied as a function of various reaction parameters and was determined from the increase in the weight of the original polymer and the estimation of pyridine pendants in the homopolymer‐free graft copolymer. Although making the polymer basic in character, this modification retained the hydrophilic nature of polyacrylamide. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2613–2620, 2002
Studies on isotactic poly(phenyl glycidyl ether)‐modified epoxy resins. II. Toughening of epoxy resins
Authors: Zhang Zheng , Yu Yunzhao 
Published: August 2002

AbstractA semicrystalline polymer, isotactic poly(phenyl glycidyl ether) (i‐PPGE) was used as a modifier for epoxy resin; 1,8‐Diamino‐p‐methane (MNDA) and 4,4′‐Diamino diphenyl sulfone (DDS) were used as curing agents. In the MNDA‐cured resins, the dispersed phase were spherical particles with diameters in the range of 0.5–1.0 μm when the resin was blended with 5 phr i‐PPGE. In the DDS‐cured resins, the particle size distribution of the dispersed phase was much wider. The difference was traced back to the reactivity of the curing agent and the different regimes used for curing. Through dynamic mechanical analysis, it was found that in the MNDA‐cured systems, i‐PPGE had a lower crystallinity than in the DDS‐cured system. In spite of the remarkable difference in the morphology and microstructure of the modified resins cured with these two curing agents, the toughening effects of i‐PPGE were similar for these resins. The critical stress intensity factor (KIC) was increased by 54% and 53%, respectively, for the resins cured by DDS and by MNDA, blending with 5 phr of the toughner. i‐PPGE was comparable with the classical toughners carboxyl‐terminated butadiene‐acrylonitrile copolymers in effectiveness of toughening the epoxy resin. An advantage of i‐PPGE was that the modulus and the glass‐transition temperature of the resin were less affected. However, this modifier caused the flexural strength to decrease somewhat. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1223–1232, 2002; DOI 10.1002/app.10445
Redox initiation of copolymerization of styrene with hydroxyl terminated polybutadiene using Ce(IV) as an oxidant
Authors: Bajpai Anjali , Simon Joshy 
Published: August 2002

AbstractRadical polymerization of styrene (St) with hydroxyl‐terminated polybutadiene (HTPB) using Ce(IV) as an oxidant was carried out under nitrogen atmosphere. The formation of styrene–butadiene block copolymer was confirmed by 1H‐NMR and IR spectroscopy. The variation in reaction parameters affected the yield of the product. St homopolymer formation under the reaction conditions used is ruled out. Crosslinking of polybutadiene chains through the styryl radical on growing block copolymer chains is suggested from viscosity and swelling measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 244–256, 2002
Study of the epoxy system BADGE (n = 0)/1,2‐DCH/CaCO3 filler by DMA and DSC
Authors: Núñez Lisardo , Núñez M. R. , Villanueva M. , Castro A. , Rial B. 
Published: August 2002

AbstractThe influence of an inorganic filler, CaCO3, on the curing kinetics of an epoxy system composed of diglycidyl ether of bisphenol A [BADGE (n = 0)], 1,2‐diaminecyclohexane (1,2‐DCH), and CaCO3 filler was studied by DMA and DSC. Different contents of filler in the range from 10 to 30%, referred to the total weight of the mixture, were tried. It was found that maximum reproducibility of the results and better performance correspond to a filler content of 20%. As usual, the Tg's obtained by DMA and DSC are different at 10–20°C. The results obtained from this study were compared with those corresponding to the system BADGE (n = 0)/1,2‐DCH without filler; the Tg for this last system is higher than that for the system with filler incorporated, whereas E′ and Mc (molecular weight between repetition units) are lower for the system without filler. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 366–370, 2002
Effects of spin finish on fiber surface hardness: An investigation with atomic force microscopy and frictional measurements
Authors: Kamath Y. K. , Ruetsch S. B. , Petrovicova E. , Kintrup L. , Schwark H.‐J. 
Published: August 2002

AbstractSpin finishes are applied to melt‐spun fibers to protect them from abrasion during processing. The principal component of the fiber finish is a lubricant, which generally is a random or block copolymer of ethylene oxide/propylene oxide. Although these polymers do not penetrate the fiber because of their high molecular weight, depending on the nature of the fiber polymer, they interact to cause changes in the hardness of the fiber surface. This happens to be the case with acidic polymer fibers such as nylon‐6 and polyester [poly(ethylene terephthalate], both of which are softened by the ethylene oxide/propylene oxide lubricant. We used atomic force microscopy with nanoindentation capability to study the effect of lubricants on the microhardness of nylon‐6 and poly(ethylene terephthalate) fiber surfaces. Softening of the fiber surface by plasticization generally results in an increase in fiber friction because of shear deformation at the interface. We made an effort to determine the friction of fibers against a hard stainless steel surface after coating them with the finish lubricant for different lengths of time. The relevance of these results to fiber processing is discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 394–414, 2002
Positron annihilation lifetime studies of gas sorption and desorption in polyethylene and poly[1‐(trimethylsilyl)‐1‐propyne]
Authors: Mohsen M. , Gomaa E. A. H. , Schut H. , Van Veen A. 
Published: August 2002

AbstractThe variation of free‐volume parameters (lifetime, intensity, and distribution) after sorption and desorption of CO2 and CH4 gases in the glassy polymer poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP) and in the rubbery high‐density polyethylene (HDPE) and low‐density polyethylene (LDPE) were determined by the PAL technique. Size distributions deduced from PAL measurements reveal the presence of large free‐volume holes in PTMSP with an average size of 0.725 nm3 and intensity of 22% in addition to a free‐volume hole size of 0.197 nm3 with an intensity of 11%. In polyethylene free‐volume hole sizes of 0.107 and 0.153 nm3 with intensities of 21% and 25% could be deduced for HDPE and LDPE, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 970–974, 2001
Preparation of high molecular weight poly(vinyl alcohol) with high yield using low‐temperature solution polymerization of vinyl acetate
Authors: Lyoo Won Seok , Han Sung Soo , Choi Jin Hyun , Ghim Han Do , Yoo Sang Woo , Lee Jinwon , Hong Sung Il , Ha Wan Shik 
Published: August 2002

AbstractVinyl acetate (VAc) was solution‐polymerized in tertiary butyl alcohol (TBA) and in dimethyl sulfoxide (DMSO) having low chain transfer constant at 30, 40, and 50°C, using a low temperature initiator, 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN). The effects of polymerization temperature and initiator concentration were investigated in terms of polymerization behavior and molecular structures of poly(vinyl acetate) (PVAc) and corresponding poly(vinyl alcohol) (PVA) obtained by saponification with sodium hydroxide. The polymerization rates of VAc in TBA and in DMSO were proportional to the 0.49 and 0.72 powers of ADMVN concentration, respectively. For the same polymerization conditions, TBA was absolutely superior to DMSO in increasing the molecular weight of PVA. In contrast, TBA was inferior to DMSO in causing conversion to polymer, indicating that the initiation rate of VAc in TBA was lower than that in DMSO. These effects could be explained by a kinetic order of ADMVN concentration calculated using initial rate method and by an activation energy difference of polymerization obtained from the Arrhenius plot. Low‐temperature solution polymerization of VAc in TBA or DMSO by adopting ADMVN proved successful in obtaining PVA of high molecular weight (number–average degree of polymerization (Pn): 4100–6100) and of high yield (ultimate conversion of VAc into PVAc: 55–80%) with diminishing heat generated during polymerization. In the case of bulk polymerization of VAc at the same conditions, maximum Pn and conversion of 5200–6200 and 20–30% was obtained, respectively. The Pn and lightness were higher, and the degree of branching was lower with PVA prepared from PVAc polymerized at lower temperatures in TBA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1003–1012, 2001
Phase behavior and molecular mobility in polyurethane/styrene–acrylonitrile blends
Authors: Vatalis A. S. , Kanapitsas A. , Delides C. G. , Viras K. , Pissis P. 
Published: August 2002

AbstractDifferential scanning calorimetry (DSC), thermally stimulated depolarization currents (TSDC) techniques, dielectric relaxation spectroscopy (DRS), and dynamic mechanical thermal analysis (DMTA), covering together a wide range of temperatures and frequencies, were employed to investigate molecular mobility and microphase separation in blends of crosslinked polyurethane (PUR) and styrene–acrylonitrile (SAN) copolymer, prepared by reactive blending with polymer polyols. The results by each technique indicate that the degree of microphase separation of PUR into hard‐segment (HS) microdomains and soft‐segment (SS) microphase increases on addition of SAN. The various techniques were critically compared to each other, with respect to their characteristic time and length scales, on the basis of activation diagrams (Arrhenius plots). The results show that for the dynamic glass transition of the PUR SS microphase the characteristic time scales at the same temperature are similar for DMTA, DSC, and TSDC and shorter for DRS. In terms of fragility, the PUR/SAN blends are classified as fragile systems. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1071–1084, 2001