bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bulk and surface modification of silicone rubber for biomedical applications
Authors: Abbasi Farhang , Mirzadeh Hamid , Katbab Ali‐Asgar 
Published: October 2002

AbstractAttempts have been made to modify the surface and bulk properties of polydimethylsiloxane (PDMS) polymers to improve their properties for biomedical applications. Laser‐induced surface grafting of poly(2‐hydroxyethyl methacrylate) (PHEMA) and a sequential method for preparation of interpenetrating polymer networks (IPNs) of PDMS/PHEMA were used for surface and bulk modifications, respectively. A major difference between these two methods and other modification techniques is their unique potentiality to modify a specific section of a polymeric sample. The modified PDMS samples have been studied by attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, water contact angle measurement, scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), and platelet adhesion measurement.© 2002 Society of Chemical Industry
Thermally stable and high molecular weight poly(propylene carbonate)s from carbon dioxide and propylene oxide
Authors: Zhu Q , Meng Y Z , Tjong S C , Zhao X S , Chen Y L 
Published: October 2002

AbstractThe copolymerization of carbon dioxide and propylene oxide was carried out to afford alternating poly(propylene carbonate) in high yield. Thermal stable and high molecular weight copolymers were successfully obtained by optimizing the reaction conditions. The catalyst used was zinc glutarate supported on a perfluorinated compound containing 7–12 carbon atoms. Copolymerization parameters, such as the ratio of propylene oxide to catalyst, stirring strength and purity of propylene oxide, were studied. The alternating copolymer with a molecular weight of 56 100 in a very high yield (126 g polymer per gram of catalyst) was achieved, which is the highest yield ever reported. The thermal and mechanical properties of the alternating PPC copolymer were examined by the means of modulated differential scanning calorimetry (MDSC), thermogravimetric analysis (TGA) and tensile test. MDSC and TGA results showed that the alternating PPC copolymer exhibits an extremely high glass transition temperature (maximum 46.46 °C) and decomposition temperature (255.8 °C) when compared to those values reported in literature. Tensile test revealed that thin film of alternating PPC copolymer exhibits superior mechanical strength.© 2002 Society of Chemical Industry
Preparation and properties of acrylic polymers/titania hybrid materials prepared by the in situ sol–gel process
Authors: Perrin F X , Nguyen V N , Vernet J L 
Published: October 2002

AbstractHybrid inorganic–organic materials based on a methyl methacrylate–n‐butyl methacrylate–methacrylic acid terpolymer have been prepared by the in situ sol–gel process in the presence of tetrabutyltitanate. The whole hydrolysis–condensation process results in homogeneous and semi‐transparent films with amounts of titania ranging from 4.5 to 22%. Infra‐red spectroscopic results show that COO—Ti bonds are formed and that chelating ones are stable up to 200 °C. Thus far, it had not been possible to separate the contributions of the acid groups from the catalyst (acetic acid) and those from the polymer. However, solvent extraction results undoubtedly proved a strong interaction between the polymer and the inorganic phase through COO—Ti bonds. Mechanical properties of the hybrid films have also been investigated through microhardness measurements and dynamic mechanical analysis. The results show that the tensile properties of the composites are strongly enhanced above the glass transition temperature (Tg) of the polymer. Below Tg, the tensile properties are not significantly affected.© 2002 Society of Chemical Industry
A kinetic study of the copolymerization of substituted anilines by 1H NMR
Authors: Mav Ida , Žigon Majda 
Published: October 2002

AbstractWe investigated the kinetics of oxidative chemical copolymerization of 2‐methoxyaniline (OMA) with the following acidic substituted anilines (ANIAs): 2‐aminobenzoic acid, 3‐aminobenzoic acid, 2‐aminobenzenesulfonic acid and 3‐aminobenzenesulfonic acid by monitoring monomer depletion using 1H NMR spectroscopy. In order to characterize kinetically these new copolymerization systems, a semi‐empirical kinetic model for copolymerization systems with a large difference in monomer reactivities was used, whereas the monomer reactivity ratios were determined by employing the Kelen–Tüdõs (KT) method. Owing to the much higher reactivity of OMA compared to that of ANIA monomers, the conversion of OMA starts before that of ANIA and both the initiation and propagation rates are higher than those for ANIAs. The ANIA end‐conversion is much smaller (from 21 to 31%) than that of OMA (from 75% to 90%).© 2002 Society of Chemical Industry
Grafting on polysilanes using atom transfer radical polymerisation
Authors: dos Santos Cláudio G , Parker James , Jones Richard G , Holder Simon J 
Published: October 2002

AbstractAtom transfer radical polymerisation (ATRP) was used in an attempt to prepare a graft polymer based on poly(methylphenylsilane) (PMPS). A partially bromomethylated PMPS was subjected to ATRP conditions in order to grow poly(methyl methacrylate) (PMMA) grafts onto that backbone. Following the grafting reaction, a substantial increase in molecular weight was observed by size exclusion chromatography, analysis using refractive index detection. However, a bimodal product molecular weight distribution was observed using a UV detector set at wavelengths at which only the PMPS backbone can be detected. The lower molecular weight fraction was identified as homopolymeric PMPS although it appears to include some material with short grafts, while the higher molecular weight fraction corresponds to PMPS with long grafts. These observations are interpreted as the formation of a substantial amount of PMMA that is not grafted onto PMPS through a radical process initiated independently of the ATRP. However, since MMA is barely susceptible to thermal polymerisation, this is not easily rationalised.© 2002 Society of Chemical Industry
Hyperbranched macromolecules through donor‐acceptor type copolymerization of allyl–vinylene bifunctional monomers
Authors: Rzaev Zakir M O 
Published: October 2002

AbstractPresent review is an attempt to generalize and systematize the results accumulated in synthesis of cyclolinear and hyperbranched reactive macromolecules via radical alternating copolymerization of various bifunctional monomers containing donor and acceptor type double bonds. Synthesis of hyperbranched reactive macromolecules was carried out using complex‐radical cyclocopolymerization of donor‐acceptor type bifunctional monomers such as monoallyl ester of maleic acid (MAM), allyl acrylate (AA), allyl methacrylate (AM), allyl trans‐cinnamate (AC), methylallylmaleate (MeAM), methylallylfumarate (MAF) and allyl‐α‐(N‐maleimido)acetate (AMI), and maleic anhydride (MA) and styrene (St) as typical acceptor and donor comonomers, respectively. The kinetic parameters of these reactions, constants of cyclization, complex‐formation and copolymerization, as well as the ratios of chain growth rates for the participation of monomeric charge transfer complexes and free monomers, were all determined. It was demonstrated that in the studied systems, copolymerizations predominantly proceed according to alternating mechanism with formation of macromolecules having cyclolinear structure in the steady‐state and hyperbranched structure in the high conversion conditions. It was shown that formation of linear and hyperbranched macromolecules containing allyl or vinylene groups in the side chain occurs selectively carry out and depends on the nature of used comonomer. General schemes and proposed mechanism of hyperbranching and crosslinking reactions were also described. Some useful properties of synthesized reactive copolymers were discussed.© 2002 Society of Chemical Industry.
Preliminary study of the non‐emissive thermal rearrangement of novel N‐cyanates to rigid rod polymers
Authors: Hay John N , Martin Philip S , Bird Clive W , Hormozi Neda 
Published: October 2002

AbstractNovel materials, both monomeric and polymeric, were synthesised to study the non‐emissive thermal rearrangement of N‐cyanates. These materials undergo an exothermic rearrangement, at temperatures in the range of 150–300 °C, to fused heterocyclic products. The series of N‐cyanate polymeric materials was characterised by Fourier‐transform infrared spectroscopy (FTIR) and modulated differential scanning calorimetry (DSC) as a preliminary assessment of their use as processable precursors to rigid rod polymers.© 2002 Society of Chemical Industry
Preparation of N,N‐dilauryl chitosan Langmuir–Blodgett film
Authors: Li Mingchun , Xin Meihua , Miyashita Tokuji 
Published: October 2002

AbstractN,N‐Dilauryl chitosan pentamer, synthesized by the reacting chitosan and lauryl aldehyde, was spread on a water surface from chloroform solution to investigate its monolayer behaviour. The condensed monolayer formed had collapse pressure of 50 mN m−1 and was transferred successful onto a solid support by the Langmuir–Blodgett (LB) technique giving a chitosan derivative ultrathin LB film with highly ordered layer structure and smooth surface. The characterization of the LB film and the monolayer on the water are discussed.© 2002 Society of Chemical Industry
Reversible addition‐fragmentation chain‐transfer (RAFT) copolymerization of vinylidene chloride and methyl acrylate
Authors: Severac Romain , Lacroix‐Desmazes Patrick , Boutevin Bernard 
Published: October 2002

AbstractThe reversible addition‐fragmentation chain‐transfer (RAFT) copolymerization of vinylidene chloride and methyl acrylate was investigated at 70 °C in benzene. Three dithioesters were synthesized in high yield by a simple and straightforward transesterification method. These dithioesters were successfully used as reversible chain‐transfer agents, as demonstrated by the increase of molecular weight with conversion, a relatively low polydispersity index (Ip = 1.5) in comparison with a blank experiment (Ip = 1.9), first‐order polymerization kinetics and efficient chain extension. Nevertheless, a transfer reaction to vinylidene chloride monomer was considered to address the limitations of the RAFT process for this system. Moreover, a retardation effect was noticeable on the kinetics, depending on the structure and concentration of the transfer agent, leading to lower rate of polymerization for lower targeted molecular weights.© 2002 Society of Chemical Industry
Novel hydrogels based on methacrylate‐modified agarose
Authors: Paepe Ilse De , Declercq Heidi , Cornelissen Maria , Schacht Etienne 
Published: October 2002

AbstractHydrogels based on agarose were prepared aiming to obtain flexible, firm and transparent materials suitable for biochemical applications. The kinetics of gelation were studied by means of rheology. Agarose was chemically modified by introduction of methacrylate side‐groups. The latter can be crosslinked to result in a network structure. The gel formation of the modified agarose is a combinatioin of physical gelation and chemical crosslinkage. The water‐soluble agarose obtained after derivatization was crosslinked by UV‐irradiation in the presence of a water soluble photoinitiator. The effect of storage time before chemical crosslinking has been examined and has a large influence on the final storage modulus and the contribution of the chemical and physical network strength towards the total network strength. The influence of the degree of modification on the final mechanical properties of the material has been examined by texturometry.© 2002 Society of Chemical Industry
Surface modification of polyimide film by ion implantation
Authors: Kim Jong‐Taek , Park Jong‐Kwan , Lee Duck‐Chool 
Published: October 2002

AbstractThe influence of ion implantation on the surface properties of polyimide was studied. We investigated microhardness, friction, wear and wettablility of polyimide. Energies of 50 keV and 200 keV were used, with doses ranging from 1 × 1013 to 1 × 1016 ion cm−2. The implanted ion species were B, N and Ar. The microhardness of polyimide increased after implantation for doses higher than 1 × 1015 ion cm−2. A reduction of the friction coefficient was in most cases correlated with a reduction of wear. The contact angles of water for B‐ and N‐implanted polyimide decreased, as the doses increased at energies of 50 keV and 200 keV. As time elapsed, the contact angle for B‐ and N‐implanted polyimide films gradually increased and finally approached the initial value under ambient room conditions. However, the contact angle of Ar‐ion‐implanted polyimide did not change under ambient room conditions, even after a few months had elapsed.© 2002 Society of Chemical Industry
Dynamic mechanical analysis of an epoxy/thermoplastic blend: polymerization‐induced phase separation
Authors: López Joaquín , Ramírez Carmen , Abad María J , Barral Luis , Cano Jesús , Díez Francisco 
Published: October 2002

AbstractPhase separation behaviour and analysis of the morphologies for a commercial epoxy resin based on tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) with 4,4′‐diaminodiphenylsulfone (DDS) as hardener and blended with different amounts of poly(styrene‐co‐acrylonitrile) (SAN) thermoplastic, have been studied by dynamic mechanical analysis (DMA) supported by other techniques. In comparison with the neat system, the modified systems reach gelation and vitrification faster. These events have been assigned at the onset and the end of the storage modulus signals E′ in a DMA curve (E′ versus time). The results are explained by a phase‐separation phenomenon induced by polymerization. Scanning electron microscopy (SEM), focused on phase separation, has revealed a sea‐island type of morphology for low thermoplastic contents and an epoxy‐nodular or phase inverted structure for high thermoplastic contents.© 2002 Society of Chemical Industry
Effects of NaCl on steady rheological behaviour in aqueous solutions of hydrophobically modified polyacrylamide and its partially hydrolyzed analogues prepared by post‐modification
Authors: Feng Yujun , Grassl Bruno , Billon Laurent , Khoukh Abdel , François Jeanne 
Published: October 2002

AbstractThe influences of NaCl on the steady rheological behaviour of aqueous solution were investigated for a hydrophobically modified polyacrylamide (HMPAM) and its hydrolyzed derivatives (HHMPAM) prepared by post‐modification. The apparent viscosity (ηapp) and reduced viscosity (ηred) were measured as a function of NaCl content. As salinity increased, ηred decreased for both HMPAM and HHMPAM in dilute regime; in the semidilute solution, a continuous increase of ηred was observed for HMPAM while ηred passed through a minimum in the case of HHMPAM. At a given polymer concentration in semidilute regime, both shear thickening and anti‐thixotropic properties were observed as a function of salinity and hydrolysis degree, as well as ageing time. Dilatancy was observed over a range of shear rates beyond which solutions behaved as classical polymer systems. When salinity exceeded a critical value, dilatancy and anti‐thixotropy appeared as increasing functions of ionic strength and decreasing functions of hydrolysis degree. Prolongation of ageing time strongly enhanced both shear thickening and anti‐thixotropic behaviors. These results are interpreted by the changes of the relative numbers of intra‐ and intermolecular associations, and the participation of free hydrophobes in the formation of clusters under shear.© 2002 Society of Chemical Industry
Improvement of the mechanical properties of poly(D,L‐lactide) by orientation
Authors: Grijpma Dirk W , Altpeter Hanno , Bevis Michael J , Feijen Jan 
Published: October 2002

AbstractOriented, amorphous poly(D,L‐lactide) was obtained by drawing injection moulded specimens at temperatures below the glass transition temperature of the polymer and by a non‐conventional injection moulding process in which the melt is cooled under oscillating shear conditions (SCORIM). In both cases effective molecular orientation is achieved, allowing the preparation of degradable devices with much improved tensile properties and impact behaviour when compared to the non‐oriented material.© 2002 Society of Chemical Industry
Direct visualization of microstructures in hydrophobically modified polyacrylamide aqueous solution by environmental scanning electron microscopy
Authors: Feng Yujun , Luo Pingya , Luo Chuanqiu , Yan Qituan 
Published: October 2002

AbstractEnvironmental scanning electron microscopy (ESEM) is an improved technique which permits the observation of samples in their native state, requiring neither sample preparation nor surface coating, and so avoids losing the original characteristics of the observed specimens. By use of a differential pumping aperture system and a secondary electron detector, the environmental conditions in the sample chamber can be varied and accommodated to the properties of the samples. This newly developed technique is used in this work to characterize the microstructures of hydrophobically modified polyacrylamide (HMPAM) and its unmodified precursor in aqueous solution. The microstructures were directly visualized by sublimation of the ice in freeze‐dried samples. It is found that three‐dimensional network structures spread throughout the whole solution for both the modified and unmodified polymers when the polymer concentration is equal to or higher than the polymer critical association concentration (CAC); when the polymer concentration is below the CAC, a sparse network structure could be seen in the solutions of modified polymer, whereas no such phenomenon is found in unmodified polymer solutions. The network units of the microstructures in the solutions of modified polymer are displayed as regularly distributed hexagons, while those of unmodified polymer appear as irregular circles. The observed results are interpreted by a proposed association model.© 2002 Society of Chemical Industry
Psychopharmacological profiles of Leucas Lavandulaefolia Rees
Authors: Mukherjee Kakali , Saha B. P. , Mukherjee Pulok K. 
Published: October 2002

AbstractMethanol extract of Leucas lavandulaefolia (LLFE) was evaluated for different psychopharmacological profiles with various animal models in rats and mice. The extract showed a potential reduction in spontaneous activity and caused a significant decrease in exploratory behavioural pattern by the head dip and Y‐maze test. It also showed a significant reduction in muscle relaxant activity by rotarod, 30 ° inclined screen and traction tests. The extract showed a remarkable potentiation of pentobarbitone induced sleeping time in mice. Copyright © 2002 John Wiley & Sons, Ltd.
Effect of valepotriates (valerian extract) in generalized anxiety disorder: a randomized placebo‐controlled pilot study
Authors: Andreatini Roberto , Sartori Vânia A. , Seabra Maria L. V. , Leite José Roberto 
Published: October 2002

AbstractThe aim of the present study was to carry out a controlled pilot study on the putative anxiolytic effect of valepotriates. Thirty‐six outpatients with generalized anxiety disorder (DSM III‐R), after a 2‐week wash‐out, were randomized to one of the following three treatments for 4 weeks (n = 12 per group): valepotriates (mean daily dose: 81.3 mg), diazepam (mean daily dose: 6.5 mg), or placebo. A parallel, double‐blind, flexible‐dose, placebo‐controlled design was employed. No significant difference was observed among the three groups at baseline or in the change from baseline on the Hamilton anxiety scale (HAM‐A) or in the trait part of the state‐trait anxiety inventory (STAI‐trait). Moreover, the three groups presented a significant reduction in the total HAM‐A scores. On the other hand, only the diazepam and valepotriates groups showed a significant reduction in the psychic factor of HAM‐A. The diazepam group also presented a significant reduction of the STAI‐trait. Although the principal analysis (HAM‐A between group comparison) found negative results (probably due to the small sample size in each group), the preliminary data obtained in the present study suggest that the valepotriates may have a potential anxiolytic effect on the psychic symptoms of anxiety. However, since the number of subjects per group was very small, the present results must be viewed as preliminary. Thus, further studies addressing this issue are warranted. Copyright © 2002 John Wiley & Sons, Ltd.
Antimutagenic effects of black tea (World blend) and its two active polyphenols theaflavins and thearubigins in Salmonella assays
Authors: Gupta S. , Chaudhuri T. , Seth P. , Ganguly D. K. , Giri A. K. 
Published: October 2002

AbstractAlmost two thirds of the world population consume tea everyday. Tea is processed differently in different parts of the world to give green (20%), black (78%) or oolong tea (2%). The antimutagenic and anticarcinogenic activities of green tea were extensively investigated compared with those of black tea. Considering the potent antimutagenic effects of green tea we recognized the need to evaluate the antimutagenic effects of black tea (World Blend Tea, Southern Tea Co., Marietta, GA) in Salmonella strains TA97a, TA98, TA100 and TA102 in preincubation tests, both with and without S9 activation. Attempts have also been made to compare the results of the tea extracts with their two active polyphenols theaflavins and thearubigins. Antimutagenicity assays were carried out in bacterial plates treated with different concentrations (1%, 2.5%, 5%, 10% and 20%) of tea extracts against known bacterial mutagens sodium azide, 4‐nitro‐o‐phenylenediamine, cumine hydroperoxide, 2‐aminofluorene and danthron. A significant decrease in the number of revertant colonies was observed in the plates treated with 1% to 20% of tea extract plus positive mutagen when compared with positive mutagen only. Both the active polyphenols theaflavins and thearubigins extracted from the black tea (World blend) also showed significant antimutagenic effects against known positive compounds in these strains. In the experiments with S9 activation, the antimutagenic effects were significantly higher. These results indicate that black tea and its two polyphenols have significant antimutagenic effects in Ames Salmonella assays. Copyright © 2002 John Wiley & Sons, Ltd.
Studies on the antiinflammatory activity of Betula alnoides bark
Authors: Sur Tapas Kumar , Pandit Srikanta , Battacharyya Dipankar , Kumar C. K. Ashok , Lakshmi S. Mohana , Chatttopadhyay D. , Mandal Subhash C. 
Published: October 2002

AbstractThe antiinflammatory activity of Betula alnoides extract was evaluated in acute and subacute inflammation models. The extract was also evaluated for antiinflammatory activity in sheep RBC induced sensitivity and in membrane stabilization models. Except for the sheep RBC induced sensitivity model, the extract showed significant antiinflammatory activity. Copyright © 2002 John Wiley and Sons, Ltd.
Studies on essential oils: Part 10; Antibacterial activity of volatile oils of some spices
Authors: Singh G. , Kapoor I. P. S. , Pandey S. K. , Singh U. K. , Singh R. K. 
Published: October 2002

AbstractThe essential oils extracted from the seeds of seven spices, Anethum graveolens, Carum capticum, Coriandrum sativum, Cuminum cyminum, Foeniculum vulgare, Pimpinella anisum and Seseli indicum have been studied for antibacterial activity against eight pathogenic bacteria, causing infections in the human body. It has been found that the oil of C. capticum is very effective against all tested bacteria. The oil of C. cyminum and A. graveolens also gave similar results. These oils are equally or more effective when compared with standard antibiotics, at a very low concentration. Copyright © 2002 John Wiley & Sons, Ltd.