bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of novel rod–coil diblock copolymers of poly(methyl methacrylate) and liquid crystalline segments of poly(2,5‐bis[(4‐methoxyphenyl)oxycarbonyl] styrene)
Authors: Zhang Hai‐Liang , Chen Xiaofang , Wan Xinhua , Zhou Qi‐Feng , Woo E M 
Published: January 2003

AbstractLiquid crystalline diblock copolymers with different molecular weights and low polydispersities were synthesized by atom transfer radical polymerization of methyl methacrylate (MMA) and 2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene (MPCS) monomers. The block architecture (coil‐conformation of MMA segment and rigid‐rod of MPCS segment) of the copolymer was experimentally confirmed by a combination of 1H nuclear magnetic resonance and gel permeation chromatograph techniques. The liquid crystalline behaviour of the copolymer was studied using differential scanning calorimetry and polarized optical microscope. It was found that the liquid crystalline behaviour was dependent on the number average molecular weight of the rigid segment. Only those copolymers with Mn(GPC) of the rigid block above 9200 g mol−1 could form liquid crystalline phases higher than the glass transition temperature of the rigid block. The random copolymers MPCS‐co‐MMA were also synthesized by conventional free radical polymerization. The molar content of MPCS in MPCS‐co‐MMA had to be higher than 71% to maintain liquid crystalline behaviour.© 2003 Society of Chemical Industry
Crystallization and morphology of metallocene polyethylenes with well‐controlled molecular weight and branching content
Authors: Peng Ya , Fu Qiang , Chiu Fang‐Chyou 
Published: January 2003

AbstractThe crystallization and morphology of some metallocene polyethylenes with well‐controlled molecular weight and branching content were investigated by DSC, WAXD, PLM and SALS. The banded spherulites observed in linear PE are not seen in crystallization of branched PEs. The small spherulites with small lamellae or fringed micelle crystals are formed when branching content is higher, as suggested by PLM and SALS. The expansion of the unit cell was observed by WAXD as the molecular weight and branching content increased. At even higher branching content (more than 7 mol%), a shrinkage of the unit cell was seen, probably due to a change of crystal morphology from lamellar‐like crystals to fringed micelle‐like crystals. Crystallization temperature, melting point and crystallinity are greatly decreased for branched PEs compared with linear PEs. The equilibrium melting temperature cannot be determined via the Hoffman–Weeks approach for branched PEs since Tm is always 5–6 °C higher than Tc and there is no intercept with the Tm = Tc line. Our results show a predominant role of branches in the crystallization of polyethylene.© 2003 Society of Chemical Industry
Study on controlled radical alternating copolymerization of styrene with maleic anhydride under UV irradiation
Authors: Wu De‐Cheng , Hong Chun‐Yan , Pan Cai‐Yuan , He Wei‐Dong 
Published: January 2003

AbstractThe copolymerization of styrene with maleic anhydride (MAh) in the presence of 1‐(ethoxycarbonyl)prop‐1‐yl dithiobenzoate was carried out under UV irradiation at room temperature, and showed ‘living’ polymerization nature which was evidenced by: linear evolution of molecular weight with conversion; and narrow molecular weight distribution (Mw/Mn = 1.08–1.20). The compositional analysis and the sequence structural information of the copolymer obtained from Distortionless Enhancement by Polarization Transfer (DEPT) NMR experiments demonstrated that the copolymers obtained possess strictly alternating structure.© 2003 Society of Chemical Industry
New aspects of unsaturated polyester resin synthesis. Part I: modelling and simulation of reactant sequence length distributions in stepwise polymerization
Authors: Zetterlund Per B , Gosden Ray G , Johnson Anthony F 
Published: January 2003

AbstractThe quantification of the relationship between physical properties of polymeric products and the sequence distribution of comonomer units in a polymer chain is not an easy task. In this work, detailed consideration is given to the sequence lengths and sequence length distributions to be expected in unsaturated polyesters formed by the reaction of maleic anhydride, phthalic anhydride and a diol, a reaction which gives rise to the low molecular weight precursors used in unsaturated polyester resins. Monte Carlo methods are used to explore the effects of rate constants, reactant stoichiometry and extent of reaction on the microstructure of the chain. Attention is also given to structural asymmetry of the diol component and the influence of the dynamics of the ring opening of the anhydride coreactants on the products. The approach is generic and can be readily adapted for any copolymerization which proceeds by a stepwise kinetic mechanism.© 2003 Society of Chemical Industry
The effects of fillers on the chemorheology of highly filled epoxy resins: I. Effects on cure transitions and kinetics
Authors: Altmann Nara , Halley Peter J 
Published: January 2003

AbstractThis work examines the effects of level of silica filler (at 0, 10, 30, 50 wt%) on the gelation and vitrification of a model silica‐filled diglycidyl ether of bisphenol F (DGEBF)/methylenedianiline (MDA) system. An increased filler level is shown to decrease the gelation and vitrification times at low temperatures (below 80 °C). FTIR cure kinetics show that the reaction rates are increased and the activation energies of gelation are reduced at these temperatures, indicating that network formation is made easier. Entropic and catalytic reasons for this phenomenon are discussed.© 2003 Society of Chemical Industry
Rheological and mechanical properties of dynamically cured poly(vinyl chloride)/nitrile butadiene rubber thermoplastic elastomers
Authors: Mousa A , Ishiaku U S , Ishak Z A Mohd 
Published: January 2003

AbstractPlasticized poly(vinyl chloride)/nitrile butadiene rubber (PVC/NBR) thermoplastic elastomers (TPEs) were dynamically cured in the melt stage with the incorporation of a semi‐efficient curing system using a Brabender Plasticorder at 150 °C and rotor speed of 50 rev min−1. Sulfur concentration was progressively increased from zero to 1 part per hundred NBR to study the effect of dynamic curing on mechanical and rheological behaviour of the TPEs. The compounds were characterized in respect of their rheological and mechanical properties. The effectiveness of dynamic curing was studied using Brabender plastograms, a moving disc rheometer and swelling index measurement. The mechanical properties investigated include tensile strength, elongation at break, modulus at 100% elongation, tear strength and hardness. The influence of thermooxidative ageing on the mechanical properties was investigated by incubating the PVC/NBR TPEs in an air oven at 80 °C for 168 h. The torque values obtained from both rheometers increased with increasing sulfur dosage, while the swelling index decreased. The significant increase in the degree of curing evidenced by the steady reduction in the swelling index provided excellent proof of the efficiency of the dynamic curing technique. Thermo‐oxidative ageing resulted in a pronounced enhancement in mechanical properties as a function of sulfur content. This observation seems to indicate that some microstructural changes, such as the formation of new crosslinks, occur in the thermo‐oxidatively aged TPEs. This trend was supported by further reduction in the swelling index of the aged TPEs.© 2003 Society of Chemical Industry
New soybean oil–styrene–divinylbenzene thermosetting copolymers. VI. Time–temperature–transformation cure diagram and the effect of curing conditions on the thermoset properties
Authors: Li Fengkui , Larock Richard C 
Published: January 2003

AbstractA new class of thermosetting resins has been developed that is based on the cationic copolymerization of regular soybean oil (SOY), low saturation soybean oil (LSS), or conjugated LSS (CLS) with various alkene comonomers initiated by boron trifluoride diethyl etherate (BFE) or related modified initiators. The activation energy for the gelation process for these thermosets ranges from 95 to 122 kJ/mol. A time‐temperature‐transformation (TTT) isothermal cure diagram has been established for the model system LSS45–ST32–DVB15–(NFO5–BFE3) ie 45 wt% low saturation soybean oil, 32 wt% styrene, 15 wt% divinylbenzene, and 5 wt% Norway fish oil ethyl ester plus 3 wt% boron trifluoride diethyl etherate. The effect of curing conditions on the thermophysical and mechanical properties, including the mechanical damping and shape memory properties, has been subsequently investigated using this model thermoset. These findings allow the efficient optimization of desired properties for specific applications.© 2003 Society of Chemical Industry
Preparation and characterization of ethylene vinyl acetate copolymer/montmorillonite nanocomposite
Authors: Jeon Cheol Hwan , Ryu Sung Hun , Chang Young‐Wook 
Published: January 2003

AbstractEthylene vinyl acetate copolymer (EVA) and monmorillonite (MMT) nanocomposites have been investigated as a function of vinyl acetate content and molecular weight of EVA and types of substituted alkyl ammonium of MMT. It is found that vinyl acetate content and type of substituted alkyl ammonium are important factors for the intercalation behaviour of MMT in MMT/EVA nanocomposite. Maleic anhydride grafted high‐density polyethylene was used as a compatibilizer to improve the intercalation behaviour of MMT. X‐ray diffraction and transmission electron microscopy were used to characterize the intercalation/exfoliation behaviour, and mechanical properties were measured.© 2003 Society of Chemical Industry
Properties of PP/PET bicomponent melt blown microfiber nonwovens after heat‐treatment
Authors: Zhao Ron (Rongguo) , Wadsworth Larry C , Sun Christine , Zhang Dong 
Published: January 2003

AbstractPolypropylene (PP)/poly(ethylene terephthalate) (PET) bicomponent (bico) fibres are successfully melt blown in the Reicofil® meltblown (MB) pilot line commissioned at the Textiles and Nonwovens Development Center (TANDEC), the University of Tennessee, Knoxville. The bico fibers possess a cross‐sectional side‐by‐side configuration. The originally expected greater fiber crimp due to density and fine structure gradients on the different sides of the bico fibers was not commonly observed in the normal MB webs. These fabrics were exposed to dry heat for a period of time. The properties before and after the heat treatment were determined and compared to investigate the effects of heat on their properties. It was found that the bico webs are thermal dimensionally stable and many of their properties were not significantly affected. A mechanism is suggested on the thermal dimensional stability of the PP/PET bico MB webs.© 2003 Society of Chemical Industry
Studies on cellulose acetate–carboxylated polysulfone blend ultrafiltration membranes—Part II
Authors: Sajitha C J , Mohan D 
Published: January 2003

AbstractHydrophilic polysulfone ultrafiltration membranes were prepared from blends of cellulose acetate and carboxylated polysulfones of 0.43 and 0.75 degrees of carboxylation. The effects of degree of carboxylation on membrane characteristics such as compaction, pure water flux, water content and membrane hydraulic resistance, have been investigated to evaluate the performance of the membranes. The influence of the degree of carboxylation on the performance of the blend membranes of various blend polymer compositions has been investigated and also compared with earlier reports on blend membranes prepared from cellulose acetate and polysulfone or carboxylated polysulfone of 0.14 degree of carboxylation.© 2003 Society of Chemical Industry
Primary amine functionalized polystyrenes by atom transfer radical polymerization
Authors: Summers Gabriel J , Ndawuni Mzikayise P , Summers Carol A 
Published: January 2003

AbstractPrimary amine functionalized polystyrenes were prepared in quantitative yields by atom transfer radical polymerization using the adduct of 1‐(bromoethyl)benzene with 1‐(4‐aminophenyl)‐1‐phenylethylene as initiator for styrene polymerization in the presence of a copper(I) bromide/N,N,N′,N′,N″‐pentamethyldiethylenetriamine catalyst system. The polymerizations proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding primary amine functionalized polystyrenes with predictable molecular weights (Mn = 2 × 103 to 10 × 103 g mol−1), relatively narrow molecular weight distributions (Mw/Mn = 1.03–1.49), well defined chain‐end functionalities and initiator efficiencies as high as 0.92. The polymerization process was monitored by gas chromatographic analysis. The primary amine functionalized polymers were characterized by thin layer chromatography, size exclusion chromatography, potentiometry and spectroscopy. Experimental results are consistent with quantitative functionalization via the 1,1‐diphenylethylene derivative. Polymerization kinetic measurements show that the polymerization reaction follows first order rate kinetics with respect to monomer consumption and the number average molecular weight increases linearly with monomer conversion.© 2003 Society of Chemical Industry
Thermal degradation study of interpenetrating polymer network based on modified bismaleimide resin and cyanate ester
Authors: Fan Jing , Hu Xiao , Yue Chee Yoon 
Published: January 2003

AbstractInterpenetrating polymer networks (IPNs) based on different ratios of a modified bismaleimide resin (BMI/DBA) and cyanate ester (b10) have been synthesized via prepolymerization followed by thermal curing. A systematic thermal degradation study of these new BMI/DBA‐CE IPN resin systems was conducted by thermogravimetric analysis at different heating rates both in N2 (thermal stability) and in air (thermal‐oxidative stability). The cured BMI/DBA‐CE IPN resin systems show excellent thermal stability, which could be demonstrated by 5% weight loss temperature (T5%) ranging between 409 and 423 °C, maximum decomposition rate temperature (Tmax) ranging between 423 and 451 °C, and the char yields at 800 °C ranging from 37% to 41% in nitrogen at a heating rate of 10 °C min−1. The apparent activation energy associated with the main degradation stage of the cured BMI/DBA‐CE IPN resin systems was determined using the Kissinger method. The obtained results provide useful information in drawing correlation between thermal properties and structure.© 2003 Society of Chemical Industry
Stepwise polymerization of propylene and ethylene with Cr(acetylacetonate)3/MgCl2–ethylbenzoate/diethylaluminium chloride catalyst system
Authors: Shin Yong‐Woo , Nakatani Hisayuki , Uozumi Toshiya , Liu Boping , Sano Tsuneji , Nitta Koh‐hei , Terano Minoru 
Published: January 2003

AbstractDuring propylene polymerization with the Cr(acetylacetonate)3/MgCl2–Et2AlCl–ethylbenzoate catalyst system which shows high isospecificity for propylene polymerization, it was found that the chain transfer and termination reactions can be neglected. Based on this result, some stepwise polymerizations of propylene and ethylene were carried out with the same catalyst system varying polymerization conditions. The resulting copolymers were separated by temperature rising elution fractionation (TREF) and afforded two fractions which were eluted at different temperatures. From the 13C NMR, DSC and GPC analyses of each fraction, it was considered that the corresponding block copolymer existed in the fraction eluted at higher temperature.© 2003 Society of Chemical Industry
Effects of La3+‐containing additive on crystalline characteristics of isotactic polypropylene
Authors: Feng Jiachun , Chen Mingcai 
Published: January 2003

AbstractThe influence of a mixed additive of lanthanum stearate and stearic acid on the crystalline characteristics of isotactic polypropylene (iPP) has been investigated. The results of the wide‐angle X‐ray diffraction (WAXD) measurements and the melting behaviour examination by differential scanning calorimetry (DSC) show that the additive might induce a high proportion of β‐form and act as a β‐form nucleating agent. The relative content of β‐form estimated by WAXD is 33.1% in a PP containing 2.5% (by weight) of the additive. Isothermal crystallization at 130 °C, examined by DSC, reveals that the additive considerably accelerates the overall rate of crystallization: the half crystallization period t1/2, decreases from 11.7 min for pure PP to 7.3 min for PP containing 2.5% of the additive. However, the additive has no obvious influence on the nucleation mechanism and crystal growth mode. Polarized light microscopy (POM) examinations indicate that the addition of the additive to PP causes spherulites to become much finer.© 2003 Society of Chemical Industry
Comparative structural studies of poly(heptamethylene p,p′‐bibenzoate) by X‐ray diffraction, positron annihilation and microhardness
Authors: Zamfirova Galina , Krasteva Manya , Misheva Marijka , Mihaylova Milena , Pérez Ernesto , Pereña José M 
Published: January 2003

AbstractThe structure of quenched samples of a polybibenzoate with a spacer containing seven methylene units has been studied by wide angle X‐ray scattering (WAXS), microhardness (MH) methods and positron annihilation lifetime spectroscopy (PALS). It was established that the quenched samples of poly(heptamethylene p,p′‐bibenzoate) (P7MB) contain three phases simultaneously: smectic liquid crystalline, amorphous, and a small amount of crystalline one. The d‐spacing of the crystal peaks, together with the crystal and smectic domain dimensions in the direction normal to the mesogen planes and the factor of paracrystallinity, were calculated. The average distance between macromolecules determined from the position of the amorphous halo correlates with the open pore diameter obtained by the PALS analysis. On the basis of MH measurements it was considered that the phases are not uniformly distributed in the depth of the sample, so that the smectic phase prevails in the surface layer while the inner layers are partially crystalline.© 2003 Society of Chemical Industry
Recovery of gold cyanide using inherently conducting polymers
Authors: Ding Jie , Price William E , Ralph Stephen F , Wallace Gordon G 
Published: January 2003

AbstractRemoval of gold from basic solutions containing [Au(CN)2]− has been demonstrated using the inherently conducting polymer polypyrrole. Polymers containing sulfonated aromatic dopants have been found to display a significant ability to remove gold from such solutions. Experiments performed in solutions containing both gold and copper cyanide complexes indicate that the recovery process is not highly selective. However, the polypyrroles used display significantly faster rates of gold recovery than activated carbon.© 2003 Society of Chemical Industry
Novel pH, ion sensitive polyampholyte gels based on carboxymethyl chitosan and gelatin
Authors: Chen Lingyun , Du Yumin , Huang Ronghua 
Published: January 2003

AbstractNatural pH and ion sensitive polyampholyte gels were successfully prepared by blending carboxymethyl chitosan (CM‐chitosan) and gelatin using glutaraldehyde as crosslinking agent. Their swelling behaviour under the influence of pH and ionic strength of the solution has been studied, and molecular interaction and, morphology of the gels were investigated by infrared spectroscopy and scanning electron microscopy. At the isoelectric point (IEP) the blend gels shrunk most, and when pH deviated from the IEP they behaved as polycations or polyanions. A decrease in swelling degree (Ds) with rising NaCl concentration up to 0.15 M was observed for all gels, while addition of Ca2+ made them shrink due to formation of Ca2+ crosslinked bridges. The blended gels showed increasing sensitivity to pH and ionic strength as the weight fraction of CM‐chitosan increased. Two essential components seem to regulate the swelling behaviour of blended gel: the first is related to osmotic pressure difference caused by the redistribution of mobile ions; the second is related to the possible formation of interactions corresponding to hydrogen bonding and hydrophobic interactions.© 2003 Society of Chemical Industry
The aspartimide problem in Fmoc‐based SPPS. Part I
Authors: Mergler M. , Dick F. , Sax B. , Weiler P. , Vorherr T. 
Published: January 2003

AbstractA variety of Asp β‐carboxy protecting groups, Hmb backbone protection and a range of Fmoc cleavage protocols have been employed in syntheses of the model hexapeptide H‐VKDGYI‐OH to investigate the aspartimide problem in more detail. The extent of formation of aspartimide and aspartimide‐related by‐products was determined by RP‐HPLC. This study included three new Fmoc‐Asp‐OH derivatives: the β‐(4‐pyridyl‐diphenylmethyl) and β‐(9‐phenyl‐fluoren‐9‐yl) esters and also the orthoester Fmoc‐β‐(4‐methyl‐2,6,7‐trioxabicyclo[2.2.2]‐oct‐1‐yl)‐alanine. 3‐Methylpent‐3‐yl protection of the Asp side chain resulted in significant improvements with respect to aspartimide formation. Complete suppression was achieved using the combination OtBu side chain protection and Hmb backbone protection for the preceding Gly residue. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.
HRMAS NMR observation of β‐sheet secondary structure on a water swollen solid support
Authors: Rousselot‐Pailley Pierre , Boutillon Christophe , Wieruszeski Jean‐Michel , Lippens Guy 
Published: January 2003

AbstractIn this paper HRMAS NMR was used to investigate whether peptides on a peptidyl resin swollen in aqueous solution can adopt an intramolecular β‐sheet structure. A model peptide YQNPDGSQA, that was previously shown to adopt such a secondary structure in solution, (Blanco et al., J. Am. Chem. Soc., 1993) was grafted onto three different solid supports that swell in aqueous solution to examine the influence of the resin on the structure. Both parameters of resin loading and pH inside the swollen peptidyl resin proved to be important for the physicochemical behaviour of the peptide on the support. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.
Role of a two‐residue spacer in an α,β‐didehydrophenylalanine containing hexapeptide: crystal and solution structure of Boc‐Val‐ΔPhe‐Leu‐Ala‐ΔPhe‐Ala‐OMe
Authors: Padyana Anil K. , Ramakumar S. , Mathur Puniti , Jagannathan N. R. , Chauhan V. S. 
Published: January 2003

AbstractThe peptide Boc‐Val1‐ΔPhe2‐Leu3‐Ala4‐ΔPhe5‐Ala6‐OMe has been examined for the structural consequence of placing a two‐residue segment between the ΔPhe residues. The peptide is stabilized by four consecutive β‐turns. The overall conformation of the molecule is a right‐handed 310‐helix, with average (ϕ, ψ) values (−67.7°, −22.7°), unwound at the C‐terminus. The 1H NMR results also suggest that the peptide maintains its 310‐helical structure in solution as observed in the crystal state. The crystal structure is stabilized through head‐to‐tail hydrogen bonds and a repertoire of aromatic interactions laterally directed between adjacent helices, which are antiparallel to each other. The aromatic ring of ΔPhe5 forms the hub of multicentred interactions, namely as a donor in aromatic C–H···π and aromatic C–H···OC interactions and as an acceptor in a CH3···π interaction. The present structure uniquely illustrates the unusual capability of a ΔPhe ring to host such concerted interactions and suggests its exploitation in introducing long‐range interactions in the folding of supersecondary structures. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.