bluuebunny/crossref_metadata_2025 huggingface dataset:
Glycosylation of human proteinase-activated receptor-2 (hPAR2): role in cell surface expression and signalling
Authors: COMPTON Steven J. , SANDHU Sabrina , WIJESURIYA Suranga J. , HOLLENBERG Morley D.
Published: November 2002

We have analysed the role of N-linked glycosylation in regulating human proteinase-activated receptor-2 (hPAR2) expression and function. Epitope-tagged wild-type hPAR2 (wt-hPAR2) or hPAR2 that lacked glycosylation sequons (following site-directed mutagenesis) in either the N-terminus [hPAR2N30A (Asn30→Ala)], extracellular loop 2 [ECL2; hPAR2N222Q (Asn222→Gln) or hPAR2N222A (Asn222→Ala)] or both (hPAR2N30A,N222A or hPAR2N30A,N222Q) were expressed in the Chinese-hamster ovary (CHO) fibroblast cell line, Pro5. Western blot analysis of wt-hPAR2 showed mature wt-hPAR2 to have a molecular mass of 55—100kDa, and 33—48kDa following N-glycosidase F deglycosylation. FACS analysis and immunocytochemistry of the wt-hPAR2 and PAR2 mutant cell lines revealed that removal of both glycosylation sequons decreases (50% of wt-hPAR2) cell surface expression. Western blot analysis indicated that both N-linked sites are glycosylated. In functional studies, hPAR2N30A displayed a selective and significant increase in sensitivity towards tryptase. Interestingly, hPAR2N222A displayed a loss in sensitivity towards all PAR2 agonists tested. However, further analysis revealed receptor sensitivity to alanine mutations in this domain, as the more conservative substitution hPAR2N222Q displayed no change in response to PAR2 agonists. hPAR2N30A,N222Q displayed increased sensitivity towards tryptase, but a loss in sensitivity towards trypsin and the synthetic peptide SLIGRL-NH2, although this loss in sensitivity towards trypsin and SLIGRL-NH2 was secondary to changes in cell-surface expression. Finally, expression of sialic-acid-deficient wt-hPAR2 in the CHO Lec2 glycosylation-deficient mutant cell line, showed a 40kDa loss in molecular mass, in addition to a marked and selective increase in sensitivity towards tryptase. We conclude that hPAR2 N-linked glycosylation and sialylation regulates receptor expression and/or signalling.
Exogenous ferrous iron is required for the nitric oxide-catalysed destruction of the iron–sulphur centre in adrenodoxin
Authors: VOEVODSKAYA Nina V. , SEREZHENKOV Vladimir A. , COOPER Chris E. , KUBRINA Lioudmila N. , VANIN Anatoly F.
Published: November 2002

No effects of gaseous NO added at a pressure of 19.95kPa on the stability of the binuclear iron—sulphur centre (ISC) of reduced iron—sulphur protein adrenodoxin (0.2mM) have been observed using the EPR method. However, the incubation of the protein with NO in the presence of ferrous iron (1.8mM) led to complete ISC degradation, accompanied by the formation of protein-bound dinitrosyl iron complexes (DNICs; 0.3±0.1mM). Similar results were obtained when low-molecular-mass DNIC with phosphate or cysteine (1.8mM) were added to solutions of pre-reduced adrenodoxin. The degradation of the ISC was suggested to be due to the attack of the Fe+(NO+)2 group from low-molecular-mass DNICs added or formed during the interaction between NO and ferrous ions on the thiol groups in active centres of adrenodoxin. This attack leads to a release of endogenous iron from the centres, which is capable of forming both low-molecular-mass and protein-bound DNIC, thereby ensuring further ISC degradation.
α1B-Adrenergic receptor phosphorylation and desensitization induced by transforming growth factor-β
Authors: ROMERO-ÁVILA M. Teresa , FLORES-JASSO C. Fabián , GARCÍA-SÁINZ J. Adolfo
Published: November 2002

Transforming growth factor-β (TGF-β) induced α1B-adrenergic receptor phosphorylation in Rat-1 fibroblasts stably expressing these adrenoceptors. This effect of TGF-β was rapid, reaching a maximum within 30min and decreasing thereafter, and concentration-dependent (EC50 0.3pM). The phosphoinositide 3-kinase inhibitors wortmannin and LY294002, and the protein kinase C inhibitors staurosporine, Ro 318220 and bisindolylmaleimide, blocked the effect of this growth factor. α1B-Adrenergic receptor phosphorylation was associated with desensitization, as indicated by a reduction in the adrenergic-mediated production of [3H]inositol phosphates. Phosphorylation of α1B-adrenergic receptors by TGF-β was also observed in Cos-1 cells transfected with the receptor. Co-transfection of the dominant-negative mutant of the regulatory subunit of phosphoinositide 3-kinase (Δp85) inhibited the phosphorylation of α1B-adrenergic receptors induced by TGF-β. Our results indicate that activation of TGF-β receptors induces α1B-adrenergic receptor phosphorylation and desensitization. The data suggest that phosphoinositide 3-kinase and protein kinase C play key roles in this effect of TGF-β.
Transition Metal-Organic Polycarboxylate Coordination Polymer Chemistry. Hydrothermal Synthesis and Structural Characterization of a One-Dimensional Coordination Polymer [Fe(bzta)2(ox)]n (bzta = benzotriazole, ox = oxalato)
Authors: Jia Hong-Bin , Yu Jie-Hui , Xu Ji-Qing , Ding Hong , Jing Wei-Jie , Liu Yong-Jiang , Li Yi-Zhi , Xu Yan , Ye Ling , Wang Tie-Gang , Xu Jia-Ning , Li Zeng-Chun
Published: November 2002

Complex [Fe(bzta)2(ox)]n (1) was synthesized from K3[Fe(ox)3]·3H2O and benzotriazole. Single-crystal X-ray diffraction study of complex 1 has established a novel structure containing several kinds of secondary bonding interactions. All these interactions make it display a three-dimensional supramolecular network.
Derivatives of (S)-{[2-(Methoxymethyl)pyrrolidin-1-yl]methyl}ferrocene - New Planar Chiral Ligands
Authors: Šebesta Radovan , Sališová Marta
Published: November 2002

New planar chiral amino-alcohol ferrocene ligands based on (S)-2-(methoxymethyl)pyrrolidine were synthesized and employed in the enantioselective addition of diethylzinc to benzaldehyde with enantioselectivity up to 82%. The effect of planar chirality was evaluated.
Ethnic differences in prisoners
Authors: Coid Jeremy , Petruckevitch Ann , Bebbington Paul , Brugha Traolach , Bhugra Dinesh , Jenkins Rachel , Farrell Mike , Lewis Glyn , Singleton Nicola
Published: November 2002

Background

In England and Wales, persons of African–Caribbean origin are more likely to be both imprisoned and admitted to secure hospitals.

Aims

To estimate population-based rates of imprisonment in different ethnic groups, and compare criminal behaviour and psychiatric morbidity.

Method

We examined Home Office data on all persons in prison, and carried out a two-stage cross-sectional survey of 3142 remanded and sentenced, male and female, prisoners in all penal establishments in England and Wales in 1997.

Results

We confirmed high rates of imprisonment for Black people and lower rates for South Asians. Different patterns of offending and lower prevalence of psychiatric morbidity were observed in Black prisoners.

Conclusions

Despite increased risks of imprisonment, African–Caribbeans show less psychiatric morbidity than White prisoners. This contrasts with the excess of African–Caribbeans in secure hospitals, an inconsistency possibly in part due to the effects of ethnic groups on admission procedures.
Anti-microbial properties of histone H2A from skin secretions of rainbow trout, Oncorhynchus mykiss
Authors: FERNANDES Jorge M.O. , KEMP Graham D. , MOLLE M. Gerard , SMITH Valerie J.
Published: November 2002

Skin exudates of rainbow trout contain a potent 13.6kDa anti-microbial protein which, from partial internal amino acid sequencing, peptide mass fingerprinting, matrix-associated laser desorption/ionization MS and amino acid analysis, seems to be histone H2A, acetylated at the N-terminus. The protein, purified to homogeneity by ion-exchange and reversed-phase chromatography, exhibits powerful anti-bacterial activity against Gram-positive bacteria, with minimal inhibitory concentrations in the submicromolar range. Kinetic analysis revealed that at a concentration of 0.3μM all test bacteria lose viability after 30min incubation. Weaker activity is also displayed against the yeast Saccharomyces cerevisiae. The protein is salt-sensitive and has no haemolytic activity towards trout erythrocytes at concentrations below 0.3μM. Reconstitution of the protein in a planar lipid bilayer strongly disturbs the membrane but does not form stable ion channels, indicating that its anti-bacterial activity is probably not due to pore-forming properties. This is the first report to show that, in addition to its classical function in the cell, histone H2A has extremely strong anti-microbial properties and could therefore help contribute to protection against bacterial invasion.
A novel way of enhancing the electrical and thermal stability of conductive epoxy resin–carbon black composites via the Joule heating effect for heating‐element applications
Authors: El‐Tantawy Farid , Kamada K. , Ohnabe H.
Published: November 2002

The influence of Joule heating treatments and carbon black (CB) on the electrical and thermal behavior of epoxy resin composites is well described in this article. The effect of CB and Joule heating on network structure characteristics, such as shrinkability, interparticle distance between conductive particles, crosslinking density, hardness, thermoelectric power, thermal conductivity, the thermal expansion coefficient, and scanning electron microscopy, of epoxy composites was investigated. The electrical conductivity (σ) of epoxy resin correlated with the volume fraction of CB and Joule heating treatment. σ increased continuously with increasing CB content, and Joule heating increased the level of σ, which makes it attractive for electronic utilization. The σ for fresh and Joule heating samples was recorded during heating–cooling cycles. The conduction mechanism of σ for epoxy composites was identified. The activation energy and hopping energy for two batches of epoxy as a function of CB content were estimated. The hopping distance, the state density at the Fermi level, and the radius of localized wave function versus CB content were evaluated. The current–voltage–temperature characteristics of fresh and Joule heating samples of epoxy composites were demonstrated. The thermal reliability was tested by means of temperature–time characteristics when certain applied power was on and off for several cycles. The specific heat and amount of heat transfer by radiation and convection were calculated based on the energy balance model for two batches. The results indicate that the Joule heating effect is a very effective and prospective way of enhancing the electrical and thermal stability of epoxy–CB composites for consumer use as heaters and in other electronic areas such as electromagnetic shielding effectiveness. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 97–109, 2003
1H nuclear magnetic resonance study of polyurethane prepolymers from toluene diisocyanate and polypropylene glycol
Authors: Pegoraro Mario , Galbiati Alessandro , Ricca Giuliana
Published: November 2002

Polyurethane prepolymers prepared from toluene 2,4‐diisocyanate, toluene 2,6‐diisocyanate, and polypropylene glycol with a ratio between the isocyanate and hydroxyl groups equal to 2 were analyzed by 1H nuclear magnetic resonance (NMR) spectroscopy in acetone‐d6. Different temperatures and concentrations were used. Toluene 2,4‐dimethylurethane and toluene 2,6‐dimethylurethane were synthesized and used as model compounds to assign prepolymers signals. Measurements of spin–lattice relaxation time T1 by “inversion recovery” experiments were carried out on toluene 2,4‐diisocyanate, toluene 2,6‐diisocyanate, toluene 2,4‐dimethylurethane, toluene 2,6‐dimethylurethane, and polyurethane prepolymers. Differences in T1 times were used to interpret prepolymers spectra, by means of the strong observed effect on protons due to the presence of adjacent isocyanate groups. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 347–357, 2003
Mahua‐oil‐based resins for the high‐temperature curing of fly ash coatings
Authors: Tiwari Sangeeta , Saxena Mohini , Tiwari Sandeep Kumar
Published: November 2002

We attempted to prepare medium‐oil‐length glycerol alkyds based on Mahua oil. Fatty acids were isolated from the oil and used in the preparation of alkyds by the fusion method. The resins were characterized by IR spectroscopic analysis. The physicochemical and film properties of these resins were also studied. IR analysis of the resins revealed the formation of phthalate esters showing characteristic peaks at 1720 cm−1. The resin was modified with melamine formaldehyde, which cured at high temperatures. Alternatively, the resin was made to air dry with ester gum, and the curing behavior was studied. The suitability of these resins for high‐temperature curing fly ash coating applications was established. Coatings were formulated with these resins and with 40% fly ash as an extender. The coatings were characterized by standard techniques, particularly for their anticorrosive and antiabrasive properties. Resistance to corrosion was evaluated in humidity and in salt‐spray conditions. We conducted a high‐stress (two‐body) abrasion test to test the abrasive wear resistance of the coatings. The Mahua‐oil‐resin‐based fly ash coatings were suitable for application in moderately corrosive and abrasive environments. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 110–120, 2003
Some new operational modes and parameters of stress relaxation for the viscoelastic characterization of solid polymers. I. The “virtual modulus” mode
Authors: Kytopoulos V. N. , Bourkas G. D. , Sideridis E.
Published: November 2002

A new operational (functional) parameter, the so‐called virtual modulus, Ē(t), is introduced. By this, an attempt was made for the approximation of the function of the real modulus E(t), which, as known, is valid only for instantaneous loading, namely, for zero loading times. Thus, through a simple theoretical modeling and an algorithmic approach, the determination of E(t), from Ē(t), sets sail, at the end, to the solution of a Volterra integral equation of the second type, which, in turn, sets sail to the solution of a differential equation. By the aid of numerical integration and also of some experimental evidence, it seems that this solution is valid only for loading times approximately above 0.2 s, thus obtaining, in fact, a “pseudomodulus” of relaxation. To assess the validity of this pseudomodulus, the well‐known Kohlrausch–Williams–Watt (KWW) and the power‐law models were used as some crude “criteria.” By means of best fit, it appeared, at the first instance, that the so‐calculated pseudomodulus better obeys the power‐law model than it does the KWW model. This is a certain contradiction with the so‐called apparent modulus, which was obtained from experiment with a finite loading time superior to 1 s. Two other criteria that were used have shown a satisfactory proof of the validity of this modeling. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 121–137, 2003
Some new operational modes and parameters of stress relaxation for the viscoelastic characterization of solid polymers. II. The “vertical‐shift” mode and intrinsic “time–strain clock”
Authors: Kytopoulos V. N. , Bourkas G. D. , Sideridis E.
Published: November 2002

As in part I of this study, in the same manner in the present part II as well, by the same modus operandi way, an attempt was made to introduce, by means of a given operational mode, some further practical parameters for a “by‐eye” but well‐proven experimental viscoelastic characterization of a polymeric solid. Thus, through consideration of the peculiar vertical shift behavior of the apparent modulus (Ẽ) of isotactic polypropylene (iPP) and based on the KWW model, it is shown that, in an empirical and a formalistic sense, a relevant effective or equivalent (single) characteristic relaxation time can be introduced which can give some new interpretations for the linear and nonlinear viscoelastic behavior of a polymeric material, as that of a “time–strain clock,” which, as an intrinsic function, is responsable for a functional time–strain shift of the relaxation time and, at the same time, for a shift toward to a more linear or to a more nonlinear behavior. In the above context of attempts, another functional relationship was shown, the so‐called spectral shift function and its corresponding parameter of nonlinearity strength, through which some further interpretations and characterizations connected with the existence of the permanent internal stress could be made. Finally, the introduction of the so‐called spectral isostrains and their corresponding “spectral inversion point” complete the “set” of the operative parameters proposed for the above‐mentioned purpose. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 138–148, 2003
Some new operational modes and parameters of stress relaxation for the viscoelastic characterization of solid polymers. III. The area ratio mode and the intrinsic “strain–clock” function
Authors: Kytopoulos V. N. , Bourkas G. D. , Sideridis E.
Published: November 2002

The introduced area ratio mode of operation with its corresponding parameters seems to have a fairly high sensitivity to the viscoelastic response of the solid polymer. This appeared from the fact that a good distinction among the linear viscoelastic, the nonlinear viscoelastic, and the viscoplastic ranges of behavior can be made. By using a relevant rheological modeling and its corresponding algorithmical approach, in the case of isotactic polypropylene, this material can be characterized as a morphological three‐phase material consisting of an intraspherulitic crystalline, an amorphous phase, and a interspherulitic para‐crystalline phase. In this sense, the material was simulated using two models: the Poynting–Thomson and the Maxwell–Wierchert, from where a good response of the material to the first model appeared. The so‐called intrinsic “strain–clock” function and its corresponding coefficient of strength of nonlinear viscoelastic behavior, which were relieved by the experimental data, seem to be some powerful and very practical “tools” that can give a proven suplementary characterization of the material. Finally, by this intrinsic function, the existence of permanent internal stresses, was confirmed, in an indirect way, which was mentioned in part II of this study. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 149–158, 2003
The influence of the nature of organoaluminum compound on kinetic heterogeneity of active sites in lanthanide‐based diene polymerization
Authors: Sigaeva N. N. , Usmanov T. S. , Budtov V. P. , Spivak S. I. , Zaikov G. E. , Monakov Yu. B.
Published: November 2002

The influence of organoaluminum compound on kinetic heterogeneity of active sites in lanthanide‐based diene polymerization was investigated. It was shown that heterogeneity of investigated catalytic systems was displayed in the existence of four types of active centers. They are formed at the beginning of the polymerization process and produce macromolecules with lengths that are definite for each type of active centers. The organoaluminum compound's nature greatly influences the kinetic activity of polymerization centers. The method of analysis of the curves' maximum distribution on kinetic activity and the change of kinetic activity of every active centers' type were proposed, which permits the calculation of values of concentration for each type of active center separately. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 358–368, 2003
Studies on self‐assembly and characterization of polyelectrolytes and organic dyes
Authors: Lin Xianjun , Zhong Anyong , Chen Deben , Zhou Zonghua , He Bobing
Published: November 2002

Four polyelectrolyte complexes were formed through self‐assembly of poly‐N‐ethyl‐N,N‐(dimethylamino)ethyl methacrylate (PEDEM) and poly‐N‐ethyl‐4‐vinylpyridinium (PEVP) cations with methyl orange (MO) and metanil yellow (MY) anions in water. The FTIR spectra showed that the assembly was formed chiefly through electrostatic force and hydrophobic interaction between polyelectrolytes and organic dyes without new bonds emerging. The fluorescence spectra revealed that the emission waves of the complexes of PEDEM–MY and PEDEM–MO in alcohol were blue‐shifted in comparison with that of dyes in alcohol, and the emission waves of the PEVP–MY and PEVP–MO_ complexes in alcohol were red‐shifted in comparison with that of dyes in alcohol. The structure of the complexes in the solid state were also investigated by DTA and X‐ray diffraction experiments. It could be proved that the complexes were new materials formed through weak interactions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 369–374, 2003
The study of surface segregation and the formation of gradient domain structure at the blend of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers and acrylate adhesive copolymers
Authors: Lee Yongjun , Akiba Isamu , Akiyama Saburo
Published: November 2002

The effect of siloxane chain length on surface segregation of poly(methyl methacrylate)‐grafted poly(dimethyl siloxane) (PMMA‐g‐PDMS)/poly(2‐ethylhexyl acrylate‐co‐acrylic acid‐co‐vinyl acetate) [P(2EHA‐AA‐VAc)] blends was investigated. The blends of PMMA‐g‐PDMS with P(2EHA‐AA‐VAc) showed surface segregations of PDMS components. The surface enrichments of PDMS in the blends depended significantly on the PDMS chain length. Also, this blend showed the gradient domain structure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 375–380, 2003
Studies on membrane formation mechanism by the light transmission technique. I
Authors: Hao Ji Hua , Wang Shichang
Published: November 2002

New parameters, light transmission rate and minimum light transmissions, are proposed. These two parameters reflect the characteristics of the membrane‐forming system and the formation process of the membranes by phase inversion. The relationship between the light transmission and the porous structure of the membrane can be explained by the geometrical optics principles. Variation of the two parameters combining Reuvers's phase separation theory provided a convenient analytical method to predict effectively membrane morphologies. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 174–181, 2003
Effect of serum components on styrene/butyl acrylate latex film formation: An in situ examination by ultramicroscopy
Authors: Keslarek Amauri José , Galembeck Fernando
Published: November 2002

Film formation by a surfactant‐stabilized, peroxide‐initiated styrene/butyl acrylate latex was followed in situ by ultramicroscopy. The effects of latex serum components on film formation were observed first by the subjection of the latex to extensive dialysis and then by the separate addition of salt and surfactants. Domains of different particle concentrations were observed in the latex dispersion during liquid evaporation, and their positions were related to those of defects in the dry film. Films obtained with the dialyzed latex showed macroscopic defects, which were not seen in the as‐prepared latex. Partially reconstituted latex (dialyzed, with the later addition of salt but not surfactant) behaved like the as‐prepared latex. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 159–167, 2003
Photopolymerizable hyperbranched (meth)acrylated poly(amine ester)
Authors: Wei Huanyu , Kou Huiguang , Shi Wenfang , Nie Kangming , Zhan Yuchuan
Published: November 2002

A hyperbranched (meth)acrylated poly(amine ester) (HPAE‐2‐A) was synthesized by the modification of the hydroxyl end groups of the second generation of a hyperbranched poly(amine ester) with acryloyl chloride and methacrylic anhydride. The photopolymerization kinetics were investigated with photo‐differential scanning calorimetry and Fourier transform infrared. The properties of HPAE‐2‐A, including the dynamic viscosity, pendulum hardness, and shrinkage, were also studied in comparison with those of a hyperbranched methacrylated poly(amine ester) (HPAE‐2‐MA) prepared in the laboratory and traditional epoxy acrylate and epoxy methacrylate. HPAE‐2‐A polymerized rapidly under UV irradiation in the presence of a photoinitiator and had a higher final conversion of double bonds. The thermomechanical properties of UV‐cured HPAE‐2‐MA films were compared with those of EB‐cured films measured with a dynamic mechanical thermal analyzer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 168–173, 2003
Preparation and performance of high‐impact polystyrene (HIPS)/nano‐TiO2 nanocomposites
Authors: Zhang Jinzhu , Wang Xin , Lu Lude , Li Dan , Yang Xujie
Published: November 2002

High‐impact polystyrene (HIPS)/nano‐TiO2 nanocomposites were prepared by surface pretreatment of nano‐TiO2 with special structure dispersing agent (TAS) and master batch manufacturing technology. The results show that when the nano‐TiO2 content is 2%, the notched impact strength, tensile strength, and elastic modulus of HIPS/nano‐TiO2 nanocomposites increased to a maximum. This result indicates that nano‐TiO2 has both toughening and reinforcing effects on HIPS. The heat‐deflection temperature and flame‐retardance of HIPS/nano‐TiO2 nanocomposites are also obviously improved as the nano‐TiO2 content is increased. The nanocomposites manufactured by the two‐step method have better mechanical properties than that made by a one‐step method. HIPS/nano‐TiO2 nanocomposites are also non‐Newtonian and pseudoplastic fluids. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 381–385, 2003
Solvent‐free radiation‐curable polyacrylate pressure‐sensitive adhesive systems
Authors: Czech Z. , Milker R.
Published: November 2002

This article shows radiation‐curable solvent‐free pressure‐sensitive adhesive polyacrylates, their synthesis, chemical modifications, important properties and use after crosslinking with UV‐lamps and UV‐lasers for the production of self‐adhesives tapes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 182–191, 2003
Hydrosoluble copolymers of acrylamide‐(2‐acrylamido‐2‐methylpropanesulfonic acid). Synthesis and characterization by spectroscopy and viscometry
Authors: Rosa Fátima , Bordado João , Casquilho Miguel
Published: November 2002

Hydrosoluble copolymers containing sulfonic acid groups incorporated into a macromolecule were synthesized. The group of polymers studied was obtained by free radical solution polymerization, using potassium persulfate as an initiator. The copolymerization of the monomers 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) and acrylamide (AA) was carried out at different pH values of the reaction medium of the monomer mix. The copolymers were characterized by proton nuclear magnetic resonance spectroscopy (1H NMR) and Fourier transform infrared spectroscopy (FTIR). The viscosity behavior of the copolymers in NaCl solution showed a dependency on the pH of the reaction medium, with higher pH leading to lower viscosities. The acidic conditions of this medium affect the initiator decomposition rate, which is a probable cause of the viscosity variation, and the extent of decomposition increases with increasing pH. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 192–198, 2003
Pyrolysis GC‐MS of chlorinated natural rubber
Authors: Yang Dan , Li Si‐Dong , Fu Wei‐Wen , Zhong Jie‐Ping , Jia De‐Min
Published: November 2002

High‐resolution pyrolysis gas chromatography‐mass spectrometry (HRPyGC‐MS) and Fourier transform infrared spectrometry (FTIR) were used to study the structures of the chlorinated natural rubbers (CNR) prepared by two different processes. The results indicate that the fine structures of CNR prepared from “latex” and “solution” processes are different, whereas their basic structures are similar. The molecule of CNR from the “latex” process contains a few carboxyl and carbonyl groups. The rings on CNR molecular chains should be hexatomic rings. The optimum pyrolytic temperature for CNR is 445°C, with an available range from 386 to 590°C. The characteristic pyrolytic products are cyclohexane homologues. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 199–204, 2003
Environmental factors and kinetics of microbial degradation of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) in an aqueous medium
Authors: Wing Hong Lo , Yu Jian
Published: November 2002

Environmental factors such as oxygen, temperature, and microbial species may have significant effects on decomposition of biodegradable polymers. A representative biodegradable, thermoplastic polymer, poly(3‐hydroxybutyrate‐co‐hydroxyvalerate) (PHBV), was decomposed in an aqueous medium under controlled laboratory conditions by soil microbes for the intrinsic degradation kinetics and the effects of the environmental factors on polymer biodegradation. The amount of proteins, including the PHBV depolymerases, that attached to the polymer surfaces was quite constant during the period of significant mass loss of the polymer specimens. The microbial polymer degradation followed a zero‐order rate model, so the residual mass fraction of PHBV films declined linearly with time. The mixed aerobic microbial organisms from fertile soil showed a higher activity of polymer degradation than an aerobic PHBV‐producing bacterium and the mixed anaerobes in the same soil. The mixed anaerobic microorganisms from barren soil decomposed the polymer at a slower rate than the anaerobes from fertile soil, and this was attributed to fewer microbial cells in the barren soil instead of the difference in the microbial species. The temperature effect on PHBV degradation can be described with an Arrhenius equation, and the activation energy is around 16 kcal/mol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 205–213, 2003
Crystalline morphology at the interface between polyethylene‐grafted glass and polyethylene
Authors: Duchet Jannick , Gérard Jean‐François , Chapel Jean‐Paul , Chabert Bernard , Brisson Josee
Published: November 2002

Adhesion measurements performed on a polyethylene (PE)‐grafted‐glass interface showed that the structure of the PE free chains (matrix) was an important parameter. The fracture energy was higher for interfaces prepared from a linear matrix, such as high‐density polyethylene (HDPE), than for those from a branched PE [low‐density polyethylene (LDPE)]. Therefore, the microstructure of the grafted PE/PE matrix interface or interphase was investigated as a function of the molar masses of the connectors and the structure (linear or branched) of the free PE matrix chains. As the grafted chains were linear, a cocrystalline structure with free chains of the HDPE matrix was generated. PE connecting chains led to a low capacity for cocrystallization with LDPE. Cocrystallization was studied with blends based on functionalized PE chains and PE matrices. These blends were assumed to be miscible, as substantiated by a single differential scanning calorimetry (DSC) peak. The DSC analyses were confirmed by wide‐angle X‐ray scattering, which revealed a crystalline orientation of the chains in the interphase, that is, in the vicinity of the glass surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 214–229, 2003
Synthesis and characterization of acrylic acid‐grafted hydrocarbon and fluorocarbon polymers with the simultaneous or mutual grafting technique
Authors: Horsfall J. A. , Lovell K. V.
Published: November 2002

Radiation‐induced graft copolymerization has been used extensively to modify polymers with acrylic acid to impart some properties of the monomer but still maintain the strength and stability of the polymer chain. This article describes the process of the simultaneous graft copolymerization reaction for the modification of hydrocarbon‐ and fluorine‐containing polymers to produce hydrophilic membranes. The effects of the conditions of grafting, such as the radiation dose rate, the total dose, and the monomer concentration on the resulting graft copolymers are discussed in detail. The characterization of the grafted membranes is described in terms of their composition, ion‐exchange capacity, equilibrium water content, and electrolytic resistivity. It has been shown that some of these properties can be predicted from the degree of grafting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 230–243, 2003
Preparation of uniform hollow polystyrene particles with large voids by a glass‐membrane emulsification technique and a subsequent suspension polymerization
Authors: Ma Guang‐Hui , Chen Ai‐Yi , Su Zhi‐Guo , Omi Shinzo
Published: November 2002

Hollow polymer particles with large voids were prepared with styrene (St) as the main component and in the presence of a small amount of N,N′‐dimethylaminoethyl methacrylate (DMAEMA) via a glass‐membrane emulsification technique and a subsequent suspension polymerization. A mixture of the monomer, hexadecane (HD), and N,N′‐azobis(2,4‐dimethylvaleronitrile) as an initiator was used as a dispersed phase (oil phase). By the careful pushing of the dispersed phase through the pores of the glass membrane into the aqueous phase, an emulsion of fairly monodisperse monomer droplets was formed. Then, the polymerization was performed by temperature being elevated to 70°C. The aqueous phase (continuous phase) contained poly(N‐vinyl pyrrolidone) as a stabilizer, sodium lauryl sulfate as a surfactant, Na2SO4 as an electrolyte, and sodium nitrite (NaNO2) as a water‐soluble inhibitor. Results related to the effects of the HD content, DMAEMA, and the composition of the comonomer, including the crosslinker and flexible segment, on the features of the hollow particles were investigated. When the content of DMAEMA was higher than 1.0 wt % based on the total monomer, small, secondary particles were generated in the aqueous phase, but the generation was effectively prevented when DMAEMA was limited to 0.5 wt %. Hollow particles, with an average diameter of around 7 μm, were obtained with an St–DMAEMA system. The void size of the hollow particles was controlled by the HD content. When the HD content was lower (<25 wt % based on the oil phase), unbroken hollow particles were easily obtained. However, they tended to break into halves after drying when the HD content was increased to 50 wt %. A soft segment, lauryl acrylate, and a crosslinker, ethylene glycol dimethacrylate, were added to overcome this problem. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 244–251, 2003
Theoretical and experimental investigation of the swelling behavior of sodium polyacrylate superabsorbent particles
Authors: Sohn Ohgun , Kim Dukjoon
Published: November 2002

Sodium polyacrylate superabsorbent polymers were prepared in particle forms by the inverse suspension technique. The surfactant concentration effect on the polymer particle size was analyzed with molecular sieves and an optical microscope. Water absorption and desorption characteristics were analyzed by the gravimetric method. The equilibrium water uptake in sodium polyacrylate particles was strongly dependent on both the salt concentration of the aqueous media and the crosslinking density of the polymers. The polymer crosslinking density was determined from the measurement of Young's modulus and the polymer–solvent interaction parameter from the equilibrium swelling experiment. The degree of inonization was predicted from experimental measurements, and theoretical analysis was performed on the effects of the salt concentration and polymer crosslinking density on the equilibrium water swelling ratio. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 252–257, 2003
Interfacial properties of polycarbonate/liquid‐crystal polymer and polystyrene/high‐impact polystyrene polymer pairs under shear deformation
Authors: Lam Y. C. , Yue C. Y. , Yang Y. X. , Tam K. C. , Hu X.
Published: November 2002

We developed an energy model derived from the first principle for multilayer configurations to enhance our understanding of the interfacial property between two polymers under shear deformation. We carried out specific experiments satisfying the boundary and loading conditions of the model to obtain the energy dissipation factor (β), which characterized and quantified the interfacial property. Two polymer pairs, the miscible system polystyrene (PS)/high‐impact polystyrene (HIPS) and the immiscible system polycarbonate (PC)/liquid‐crystal polymer (LCP), were investigated. As expected, β was zero for PS/HIPS, reflecting the strong interaction at the PS/HIPS interface. For PC/LCP, the value of β could be significant, and its behavior was complex; it reflected the thermal sensitivity and thermal history effect of the PC/LCP interface. A positive value of β also indicated the possibility of slip at the interface and provided an explanation for the negative deviation from the rule of mixture. This complex behavior of the interface was attributed to the changes in the phases and microstructure of LCPs and, therefore, the LCP/PC interface as thermal cycling was carried out in the melting/nematic range of LCPs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 258–269, 2003
Synthesis of water‐soluble thermosensitive polymers having phosphonium groups from methacryloyloxyethyl trialkyl phosphonium chlorides–N‐isopropylacrylamide copolymers and their functions
Authors: Nonaka Takamasa , Hua Li , Ogata Tomonari , Kurihara Seiji
Published: November 2002

Water‐soluble thermosensitive polymers having phosphonium groups were synthesized by the copolymerization of N‐isopropylacrylamide (NIPAAm) with methacryloyloxyethyl trialkyl phosphonium chlorides (METRs) having varying alkyl lengths. The relative viscosities of the copolymer solutions increased with increasing content of phosphonium groups in the copolymers and decreased with increasing chain length of alkyl chains in the phosphonium groups. However, the copolymers of METR with octyl groups in phosphonium groups (METO) and NIPAAm became water insoluble with increasing contents of METO moieties in the copolymers. The transmittance at 660 nm of the copolymer solutions above the lower critical solution temperature (LCST) decreased gradually with increasing temperature and decreased with increasing chain length of alkyl chains in the phosphonium groups. The transmittance at 660 nm of the copolymer solutions above the LCST was greatly affected by the addition of neutral salts such as KCl. The copolymers of METR with ethyl groups in phosphonium groups and NIPAAm and those of METR with butyl groups in phosphonium groups and NIPAAm had high flocculating abilities against bacterial suspensions. The METO–NIPAAm copolymer was found to have a high antibacterial activity. The flocculating ability and the antibacterial activity of the copolymers were affected by not only the content of phosphonium groups but also the alkyl chain length in the phosphonium groups in the copolymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 386–393, 2003
Gas‐phase polymerization of butadiene. Data acquisition using minireactor technology and particle modeling
Authors: Bartke M. , Wartmann A. , Reichert K.‐H.
Published: November 2002

Minireactor technology has been used for kinetic studies on polymerization kinetics, phase equilibrium, and mass transfer on a very small scale. There is a nonlinear influence of temperature and pressure on the polymerization rate. The phase equilibrium can be described by a Flory–Huggins approach, with a temperature‐dependent interaction parameter. The diffusion coefficient seems to be slightly pressure dependent, and the temperature dependence can be described with an Arrhenius equation. A simple formal kinetic scheme with formation of active sites, chain propagation, chain transfer to cocatalyst, and deactivation of active sites has been applied. This kinetic scheme was implemented in two different models; they are, a particle model taking into account mass transfer and a simple chemical model with no mass transfer. In principle, both models describe the experimental results for rate and molecular weight distribution equally well, with rate constants of the same magnitude. Molecular weight distributions calculated by the chemical model are narrower. However, the chemical model gives no explanation for the experimental observed rate dependence on catalyst particle size. With increasing catalyst activity, the differences between both models become more significant and the particle model becomes more and more important. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 270–279, 2003
Preparation of heat‐resistant gradient‐index polymer optical fiber rods based on poly(N‐isopropylmaleimide‐co‐methyl methacrylate)
Authors: Wang Dong‐Jun , Gu Chen‐Bin , Chen Peng‐Lei , Liu Shi‐Xiong , Zhen Zhen , Zhang Jian‐Cheng , Liu Xin‐Hou
Published: November 2002

Using the interfacial gel polymerization method, a heat‐resistant gradient‐index polymer optical fiber (GI POF) was developed based on the copolymer of methyl methacrylate (MMA) and N‐isopropylmaleimide (IPMI) as the matrix material and bromobenzene (BB) as dopant. The gradient distribution of IPMI in the GI POF rod was determined by element analysis. IPMI had great advantage in improving glass transition temperature (Tg) and forming a gradient‐index profile. There was a significant enhancement in the heat‐resistant property in comparison with a conventional GI POF rod. The combination of high thermal stability and easy fabrication makes the novel BB–IPMI–MMA system very suitable for heat‐resistant GI POF. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 280–283, 2003
Influence of different polyesters and their molecular weight on the textural and electrooptical behavior of polymer‐dispersed liquid crystals
Authors: Kundu P. P. , Verma G. , Raina K. K.
Published: November 2002

The textural and electrooptical behavior of a nematic liquid crystal (LC) dispersed in a flexible and rigid polyester was studied. The dispersion of LC in the polymer matrix and light transmission through the polymer‐dispersed liquid crystal (PDLC) is governed by the nature of the polymer, its molecular weight, and the applied voltage. It was observed that the transmission of light and the dispersion of LC maximizes their respective values at the minimum molecular weight irrespective of the nature of the polymer and at the maximum voltage. The reason is the predominance of chain alignment over entanglement at the minimum molecular weight. As molecular weight increases, the transmission of light as well as the dispersion of LC in the polymer may increase or decrease depending on the predominance of chain entanglement or chain alignment. The alignment of LC droplets in the direction of the applied voltage is increased by an increase in the applied voltage, causing enhancement of the light transmission. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 284–289, 2003
Graft polymerization of vinyl acetate onto silica
Authors: Nguyen Van , Yoshida Wayne , Cohen Yoram
Published: November 2002

The free‐radical graft polymerization of vinyl acetate onto nonporous silica particles was studied experimentally. The grafting procedure consisted of surface activation with vinyltrimethoxysilane, followed by free‐radical graft polymerization of vinyl acetate in ethyl acetate with 2,2′‐azobis(2,4‐dimethylpentanenitrile) initiator. Initial monomer concentration was varied from 10 to 40% by volume and the reaction was spanned from 50 to 70°C. The resulting grafted polymer, which was stable over a wide range of pH levels, consisted of polymer chains that are terminally and covalently bonded to the silica substrate. The experimental polymerization rate order, with respect to monomer concentration, ranged from 1.61 to 2.00, consistent with the kinetic order for the high polymerization regime. The corresponding rate order for polymer grafting varied from 1.24 to 1.43. The polymer graft yield increased with both initial monomer concentration and reaction temperature, and the polymer‐grafted surface became more hydrophobic with increasing polymer graft yield. The present study suggests that a denser grafted polymer phase of shorter chains was created upon increasing temperature. On the other hand, both polymer chain length and polymer graft density increased with initial monomer concentration. Atomic force microscopy–determined topology of the polymer‐grafted surface revealed a distribution of surface clusters and surface elevations consistent with the expected broad molecular‐weight distribution for free‐radical polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 300–310, 2003
Poly(2‐hydroxyethyl methacrylate‐co‐ethylene dimethacrylate) as a mouse embryonic stem cells support
Authors: Horák D. , Dvořák P. , Hampl A. , Šlouf M.
Published: November 2002

A series of swellable ethylene dimethacrylate‐crosslinked poly(2‐hydroxyethyl methacrylate) (PHEMA) sheets of homogeneous (nonporous) structure or with different degrees of swelling and porosities was produced by bulk polymerization in either the absence or the presence of various diluents (porogens). Calculations performed by use of the solubility parameter δ of the reaction components indicate that the solvation conditions of the polymerization system change, depending on the solvating power of the diluent, which thus controls the porosity. Pore volume also seemed to be sensitive to the presence of the linear polymer diluent. Polystyrene (PS) showed, compared with poly(methyl methacrylate) (PMMA), a higher precipitating ability to form porous PHEMA sheets with an increased pore size because of its higher noncompatibility with newly formed crosslinked PHEMA. Given that PHEMA hydrogel is well known for its biocompatibility, it was used here as a potential carrier of cells in transplantation therapies. Attachment and growth of mouse embryonic stem (ES) cells on gelatin‐coated transparent PHEMA hydrogel substrates were examined. Two days after plating, survival and morphology of ES cells were largely similar on both PHEMA hydrogel sheets and in petri dishes as controls. This suggests that PHEMA hydrogels are likely candidates for application in transplantation therapies involving ES cells. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 425–432, 2003
Model‐free kinetics: Curing behavior of phenol formaldehyde resins by differential scanning calorimetry
Authors: He Guangbo , Riedl Bernard , Aït‐Kadi Abdellatif
Published: November 2002

Isoconversional analysis was used to treat nonisothermal DSC data and yield the dependence of activation energy on conversion during the curing process of PF resins. The shape of the dependence revealed that the curing process of PF resins displayed a change in the reaction mechanism from a kinetic to a diffusion regime. In the kinetic regime a comparative DSC experimental analysis between monomer mixtures and PF resins showed that the addition reactions between phenol and formaldehyde had been mostly completed during the synthesis of PF resins and that the main kinetic reactions contained parallel condensations in the curing process. For the diffusion regime a modified equation for the diffusion rate constant, kD= D0 exp(−ED/RT + K1α + K2α2), is proposed. This equation is in good agreement with the experimental dependence of Eα on α in the diffusion regime, which shows the effect of both temperature and conversion on diffusion. A prediction of the conversion advancement with the reaction time under isothermal condition for PF resin has been made. This prediction can be useful in practical applications for evaluating isothermal behavior of thermosetting systems from nonisothermal experimental data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 433–440, 2003