bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface modification and in vitro Blood compatibilities of polyurethanes containing γ‐Benzyl L‐glutamate segments in the main chain
Authors: Hyun Jae‐Yong , Meng Wan , Kang Inn‐Kyu , Song Dong‐Ik 
Published: April 2003

AbstractPoly(ether urethanes) containing γ‐benzyl L‐glutamate segments in the main chains (PUBLG) were synthesized from 4,4′‐diphenylmethyl diisocyanate, poly(tetramethylene glycol) and γ‐benzyl L‐glutamate oligomer as a chain extender. The surface modification of the PUBLG film was carried out by means of a hydrolysis reaction and heparin immobilization. The surface‐modified PUBLGs were then characterized by attenuated total reflection Fourier‐transform infrared (FT‐IR) spectroscopy and electron spectroscopy for chemical analysis. In vitro blood compatibility of surface‐modified PUBLGs was investigated using plasma proteins, platelets and peripheral blood mononuclear cells. Activated partial thromboplastin time was prolonged on heparin‐immobilized PUBLG (PUBLG‐H), suggesting the binding of immobilized heparin to antithrombin III. The release of serotonin from adhering platelets was significantly suppressed on PUBLG‐H when compared to the other substrates. In the peripheral blood mononuclear cells experiments, the adhesion and activation of the cells were significantly suppressed on PUBLG‐H and the amount of interleukin‐6 released from peripheral blood mononuclear cells stimulated with surface‐modified PUBLGs decreased with a decrease in peripheral blood mononuclear cells adhesion. Copyright © 2003 John Wiley & Sons, Ltd.
Morphology of P(BA‐St‐DAAM) latex particles prepared by seeded‐emulsion polymerization
Authors: Li Huaping , Kan Chengyou , Du Yi , Liu Deshan 
Published: April 2003

AbstractSeed latex particles of P(styrene‐butyl acrylate) with narrow diameter distribution were first prepared by using ammonium persulfate as initiator at 80 °C for 3 h, then seeded‐emulsion polymerization of styrene, butyl acrylate, methacrylic acid and diacetone acrylamide onto the P(styrene‐butyl acrylate) seed particles was carried out at 85 °C in the absent of emulsifier. In order to investigate the relationship between the polymerization conditions and particle morphology, three different processes of batch, swelling and semi‐continuous monomer additions were used. It was found that latex particles prepared using the swelling process showed no signs of multiphase morphology, while both batch and semi‐continuous processes gave a strawberry‐like particle morphology. A series of polymerizations was carried out using the semi‐continuous process. Results showed that the more acrylamide monomer that was used, the more distinct the phase separation was, and that different monomer feed rates resulted in the same type of particle morphology. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and characterization of trifluoromethylated poly(aryl ether ketone)s
Authors: Liu Baijun , Hu Wei , Chen Chunhai , Jiang Zhenhua , Zhang Wanjin , Wu Zhongwen 
Published: April 2003

AbstractConsiderable attention has been devoted to the preparation of fluorine‐containing polymers due to their unique properties and high‐temperature performance. In this paper, we report the synthesis of novel fluorine‐containing poly(aryl ether ketone)s with (3‐fluoromethyl)phenyl or (3,5‐difluoromethyl)phenyl moieties. Novel 3F‐polymers and 6F‐polymers are synthesized from fluorinated bisphenols and dihalides via an aromatic nucleophilic substitution reaction. The high‐molecular‐weight polymers could be obtained despite the steric effect of the bulky pendant groups. The Tgs of polymers ranged from 136 °C to 163 °C. All the polymers exhibited high thermal stability. 3F‐PEEK and 6F‐PEEK showed excellent solubility. The strong, flexible and colorless films were easily obtained by solution casting and compression molding. The near‐infrared spectra showed that the films of 3F‐PEEK and 6F‐PEEK had small light absorption at the telecommunication wavelengths of 1.3 µm and 1.55 µm. Furthermore, 3F‐PEEK, 3F‐PEEKK, 6F‐PEEK, and 6F‐PEEKK exhibited low dielectric constants. The dielectric constants were 2.70, 2.76, 2.69 and 2.78 respectively at 1 MHz. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and properties of poly(L‐lactide)‐Poly(Ethylene glycol) multiblock copolymers by coupling triblock copolymers
Authors: Chen Wenna , Luo Weijun , Wang Shenguo , Bei Jianzhong 
Published: April 2003

AbstractA series of multiblock copolymers of PLLA/PEG(PLE) with high molecular weight were synthesized by coupling PLLA‐PEG‐PLLA triblock copolymers with succinic anhydride in the presence of N‐dimethylaminopyridine(DMAP) and dicyclohexylcarbodimide (DCC). The results of the viscometry measurement, GPC and 1H NMR, elucidated that multiblock PLE copolymers with high content of short PEG segments had been successfully obtained. The thermal properties and the crystallinity were investigated by DSC and X‐ray diffraction. When LA/EG molar ratio and the length of PEG segments were the same in both multiblock and triblock copolymers, multiblock copolymers were less crystalline than the corresponding triblock ones. Mechanical testing showed that multiblock copolymers had relatively high tensile strength and large elongation. In a word, the measurements showed that this multiblock PLE copolymers had high content of short PEG segments (Mn = 2000,4000), high molecular weight (Mw∼50 000), high hydrophilicity, and good mechanical properties. The drug (5‐Fluorourecil) release behavior of these PLE multiblock copolymers had been studied in 0.10M pH7.4 phosphate buffer solution (PBS), and the releasing rate could be tailored by adjusting copolymers composition. All of these results indicated that the multiblock PLE copolymers might be useful in medical applications. Copyright © 2003 John Wiley & Sons, Ltd.
Silica‐based hybrid nonlinear optical chromophore‐trapping film prepared by sol‐gel polymerization
Authors: Ji Shengxiang , Li Ze , Zhou Xiaoshu , Cao Ming , Dai Daorong , Zhang Rongben , Li Shaojun , Ye Cheng 
Published: April 2003

AbstractA new thermal‐resistant second‐order nonlinear optical film has been prepared by in situ poling and sol–gel processing of 1,4‐phenylene bis(4‐trimethoxylsilylethylbenzoate) (PMSE) and Disperse Red 1 (DR1). The monomer, PMSE, was synthesized by Pt‐catalyzed hydrosilylation reaction followed by alcoholysis reaction. The chromophore DR1 was embedded in the crosslinked organosilicon polymeric matrix. The film was characterized by FTIR, differential scanning calorimeter (DSC), and X‐ray diffraction (XRD). The elemental analysis shows the DR1 content of the poled film to be about 11 wt%. The second‐order harmonic generation (SHG) coefficient (d33) of the film is 16.7 pm/v and its thermal stability studies demonstrate that the onset of d33 decay is about 130 °C. Copyright © 2003 John Wiley & Sons, Ltd.
Catalytic behavior of wool–Rh complex in asymmetric hydrogenation of 2‐methyl furan
Authors: He Man , Zhou Da‐Qing , Ge Hong‐Li , Huang Mei‐Yu , Jiang Ying‐Yan 
Published: April 2003

AbstractA Wool–Rh complex was prepared by the reaction of wool with RhCl3·3H2O in ethanol solution, and was found to be useful as a chiral catalyst for the asymmetric hydrogenation of 2‐methyl furan to (S)‐(+)‐2‐methyl tetrahydrofuran at 28 °C and under atmospheric hydrogen pressure.When an appropriate Rh content in the Wool–Rh complex was selected, the yield and optical yield amounted to 53.7 and 76.9%, respectively, and the Wool–Rh complex catalyst could be reused several times without any noticeable loss in its optical catalytic activity.Wool is a very cheap natural biopolymer ligand, and Wool–Rh complex is very easy to prepare, and it is a very active, enantioselective and stable chiral catalyst for asymmetric hydrogenation of 2‐methyl furan. Copyright © 2003 John Wiley & Sons, Ltd.
Preparation of silica‐supported alginic acid‐L‐glutamic acid–Pt complex and its catalytic behaviors in asymmetric hydrogenation of 4‐methyl‐2‐pentanone
Authors: Xue Lei , Li Bao‐Yu , Huang Mei‐Yu , Jiang Ying‐Yan 
Published: April 2003

AbstractA new chiral polymer–metal complex, silica‐supported alginic acid‐L‐glutamic acid–Pt complex (SiO2‐AA‐L‐Glu‐Pt), has been prepared by a very simple method and has been found to be able to catalyze the asymmetric hydrogenation of 4‐methyl‐2‐pentanone to give (R)‐(−)‐4‐methyl‐2‐pentanol in 90.8% optical yield at 30 °C and under 1 atm H2. The product and optical yields were greatly affected by the Pt content in the complex, the solvent, the 4‐methyl‐2‐pentanone/Pt molar ratio and the reaction temperature. The catalyst could be reused several times without any great change in its optical catalytic activity. Copyright © 2003 John Wiley & Sons, Ltd.
Light‐emitting alternating copolymers and their intramolecular charge transfer state
Authors: Lin Hongzhen , Yang Junlin , Zheng Min , He Qingguo , Huang Hongmin , Bai Fenglian 
Published: April 2003

AbstractTwo light‐emitting conjugated polymers alternatively involving arylenevinylene and a N‐alkyl carbazole moieties in the main chain were investigated. The formation of an intramolecular charge transfer state was probed within the repetition units of the copolymers. A tail absorption band and dual fluorescence were found for one of the copolymers, poly[(9‐(2‐ethyl‐hexyl)‐9H‐carbazol‐3,6‐ylene)‐alt‐(anthracen‐9,10‐ylene) vinylene], Cz‐PAV. Solvent polarity effects were studied by means of steady‐state spectroscopy and fluorescence‐lifetime measurements. Fluorescence emission spectra at 77 K were also explored. All the results show that a photoinduced intramolecular charge transfer state was formed in Cz‐PAV. The formation of this state may be related to the electron affinity of the acceptor group contained in the copolymer and to the molecular conformation of the copolymer. Copyright © 2003 John Wiley & Sons, Ltd.
Controlled synthesis of poly(carbosiloxane)s
Authors: Kawakami Yusuke 
Published: April 2003

AbstractDehydrocoupling polymerization of 1,4‐bis(dimethylsilyl)benzene, 1,3‐bis(dimethylsilyl)benzene, 4,4′‐bis(dimethylsilyl)benzene, and 9,9′‐bis[4‐(dimethylsilyl)‐phenyl]fluorene with water was carried out. The sequential regularity of the polymers was estimated by 1H‐NMR spectroscopy. The reactivity of SiH on the dimethylsilyl group in the dehydrocoupling reaction was found to be almost the same without any connection to the structure of the aromatic groups. Stereoregular and optically active polycarbosiloxanes were also synthesized by polyaddition, polycondensation, and ring‐opening polymerization of optically‐active monomers. Their regio‐ and stereoregularity were investigated by the 13C and 29Si‐NMR, and proved to be dependent upon the optical purity of the monomers. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and anti‐HIV activity of ­6‐amino‐6‐deoxy‐(1→3)‐β‐D‐curdlan sulfate
Authors: Borjihan Gereltu , Zhong Guiyun , Baigude Huricha , Nakashima Hedeki , Uryu Toshiyuki 
Published: April 2003

Abstract6‐Amino‐6‐deoxy‐(1→3)‐β‐D‐curdlan sulfate was synthesized in three steps. First, curdlan was azidized by lithium azide (LiN3) and carbon tetrabromide (CBr4) with triphenylphosphine (Ph3P) in dimethylformamide (DMF). Second, the azido group was reduced to an amino group with sodium borohydride (NaBH4) in dimethyl sulfoxide (DMSO) to afford 6‐amino‐6‐deoxy‐(1→3)‐β‐D‐curdlan. Third, sulfation of the amino‐group‐containing curdlan with a sulfur trioxide‐pyridine complex produced a 6‐amino‐6‐deoxy‐(1→3)‐β‐D‐curdlan sufate exhibiting high anti‐HIV (human immunodeficiency virus) activity (EC50 = 0.912 µg/ml) and low cytotoxicity (CC50 = 2512 µg/ml). Copyright © 2003 John Wiley & Sons, Ltd.
Studies on the rheological properties and compatibility of low molecular weightPC and PS polymer alloy
Authors: Liu Jun , Zhang Ji‐Gui 
Published: April 2003

AbstractThe rheological properties and compatibility of PC/PS containing SMA are determined and the possibility of the alloy being used as a new disc material is also discussed in this paper. The results showed that the ηa of the alloy decreased markedly on increasing the temperature, shear rate and PS content in the alloy. In addition, it was confirmed by DSC that PC was partly compatible with PS. The influence of SMA added into PC/PS on the compatibility was also studied. The results showed that SMA has compatibilization, apparent viscosity ηa of the systems could be lowered by the addition of the compatibilizer, and the results of DSC showed that the Tg of the PC phase got closer to the Tg of the PS phase, until it has only one Tg. Using SEM, the microstructure of the polymer alloy was studied. It indicated compatibilization was better, consistent with the result of DSC. Finally, it is discussed whether the PC/PS alloy systems with the compatibilizer could be used as the substrate material for optical disks. Copyright © 2003 John Wiley & Sons, Ltd.
Silica‐supported chitosan–osmium tetroxide complex catalyzed vicinal hydroxylation of olefins using hexacyanoferrate(III) ion as a cooxidant
Authors: Huang Kai , Liu Hong‐Wen , Dou Xi , Huang Mei‐Yu , Jiang Ying‐Yan 
Published: April 2003

AbstractSilica‐supported chitosan–osmium tetroxide complex was prepared by a very simple method. This complex (SiO2‐CS‐OsO4) has been found to be able to catalyze the dihydroxylation of styrene, α‐methyl‐styrene, 1‐heptene, 1‐octene and 1‐decene to get (R)‐(−)‐1‐phenyl‐1,2‐ethanediol, (R)‐(−)‐2‐phenyl‐1,2‐propanediol, (S)‐(−)‐1,2‐heptanediol, (S)‐(−)‐1,2‐octanediol and (R)‐(+)‐1,2‐decanediol in the presence of K3Fe(CN)6, K2CO3, t‐BuOH and water at room temperature and under atmospheric pressure. The optical yields amounted to 77.3%, 64.8%, 81.3%, 78.2% and 38.4% respectively, and the product yields were 65.5%, 70%, 89.4%, 51% and 49.6% respectively. The experimental results showed that the OsO4 content in the SiO2‐CS‐OsO4 complex greatly affected the optical yield. This new polymer–Os complex was very easy to prepare and could be reused without any appreciable change in optical catalytic activity. Copyright © 2003 John Wiley & Sons, Ltd.
Regulation of comonomer‐Sequenceand stereosequence in radical copolymerization of methyl methacrylate and styrene
Authors: Hirai Hidefumi 
Published: April 2003

AbstractThe radical copolymerization of methyl methacrylate (MMA) and styrene (St) in the presence of various metal halides was conducted to achieve the advanced regulation of comonomer‐sequence and stereosequence in the resulting copolymers. The alternation‐regulating activities of various metal halides were determined quantitatively by the MMA content in the copolymer prepared under the specific conditions. Boron trichloride, aluminum tribromide and ethyl boron dichloride were found to have large alternation‐regulating activities, yielding the strictly alternating MMA‐St copolymers with high regulation of comonomer‐sequence. The cotacticities of the ‐MMA‐St‐ diad, the ‐St‐MMA‐St‐ triad and the­‐MMA‐St‐MMA‐ triad in the alternating copolymer were determined by 1H‐ and 13C‐NMR spectroscopies. The cotacticities depend on the species and the concentrations of the metal halides, and on the polymerization temperatures. The alternating MMA‐St copolymer with the highest coheterotacticity has been prepared by using boron trichloride at − 95 °C. The mechanism of the stereosequence regulation is described in detail. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of filler loading on cure time and swelling behaviour of SMR L/ENR 25 and SMR L/SBR blends
Authors: Ismail Hanafi , Poh B T , Tan K S , Moorthy M 
Published: April 2003

AbstractThe effect of filler loading on the cure time (t90) and swelling behaviour of SMR L/ENR 25 and SMR L/SBR blends has been studied. Carbon black (N330), silica (Vulcasil C) and calcium carbonate were used as fillers and the loading range was from 0 to 40 phr. Results show that for SMR L/ENR 25 blends the cure time decreases with increasing carbon black loading, whereas silica shows an increasing trend, and calcium carbonate does not show significant changes. For SMR L/SBR blends, the cure time of carbon black, silica and calcium carbonate generally decreases with increasing filler loading. The percentage swelling in toluene and ASTM oil no 3 decreases for both blends with increasing filler loading, with calcium carbonate giving the highest value, followed by silica‐ and carbon black‐filled blends. At a fixed filler loading, SMR L/ENR 25 blend shows a lower percentage swelling than SMR L/SBR blends.© 2003 Society of Chemical Industry
Comparison of properties of acrylic–polyurethane hybrid emulsions prepared by batch and semibatch processes with monomer emulsion feed
Authors: Šebenik Urška , Golob Janvit , Krajnc Matjaž 
Published: April 2003

AbstractAqueous acrylic–polyurethane hybrid emulsions were prepared by batch and semibatch polymerization of acrylic monomer mixtures (butyl acrylate, methyl methacrylate and acrylic acid) in the presence of polyurethane dispersion. The acrylic component was introduced in the monomer emulsion feed. The weight ratio between acrylic and polyurethane components was varied to obtain different emulsion properties, microphase structure and mechanical film properties. Scanning electron microscopy, average particle size and molecular weight measurements were performed to characterize the latex systems. Mechanical properties were examined by measuring Koenig hardnesses of dried films. The average particle size increased with the acrylic/polyurethane ratio. Particles of larger than average size and, to some extent, higher than average molecular weights by batch process were formed. Koenig hardnesses decreased with increasing acrylic/polyurethane ratio. Properties of emulsions synthesized by semibatch processes were compared with the results reported for a different polyurethane dispersion. Copyright © 2003 Society of Chemical Industry
Novolak resins: structure elucidation by multidimensional NMR techniques and correlation with lithographic performance
Authors: Roy Debmalya , Basu PK , Raghunathan P , Eswaran SV 
Published: April 2003

AbstractPhoto‐active chemicals blended with novolak resins, solvents and certain other additives serve as photoresists and are the real workhorses of the burgeoning microlithography industry, which plays a key role in making electronic circuits for ICs and VLSIs at micron and sub‐micron levels. It has been realized over the years that the microstructure of these matrix polymers (novolak resins) is very crucial for better lithographic performance. Although various analytical techniques exist for characterizing novolak resins, precise and unambiguous structural details are obtained only through NMR experiments. In this paper, we review the applications of a range of NMR experimental techniques to the structure elucidation of novolak polymers and co‐polymers. Such information is seen to lead to the design of high‐performance photoresists. The optimum percentage of the different phenolic units in novolak resins, which is very crucial for lithographic performance, can also be determined using these spectroscopic techniques. Using DEPT and INEPT 13C NMR spectra of novolak resins, two formulae have been developed for quantitative estimation of the lithographic performance of photoresists. On the basis of a comparison of the NMR spectra of a photoresist before and after photolysis, the mechanism of action of a photoresist can be probed, and this should lead to a deeper insight into the design of high‐performing photoresists. Copyright © 2003 Society of Chemical Industry
Modification of cyanate ester resin by soluble polyarylates
Authors: Iijima Takao , Kunimi Takao , Oyama Toshiyuki , Tomoi Masao 
Published: April 2003

AbstractSoluble polyarylates were prepared from the reaction of 2,2‐bis(4‐hydroxyphenyl)propane (bisphenol‐A) and aromatic acid dichlorides (phthaloyl chloride and related diacid dichlorides), and used to improve the brittleness of a cyanate ester resin. The polyarylates include poly[2,2‐di(4‐phenylene)propane phthalate] (PPA), poly[2,2‐di(4‐phenylene)propane phthalate‐co‐2,2‐di(4‐phenylene)propane isophthalate] (IPPA) and poly[2,2‐di(4‐phenylene)propane phthalate‐co‐2,2‐di(4‐phenylene)propane terephthalate] (TPPA). Furthermore, a commercial polyarylate, U‐polymer, was also used as a modifier. The morphologies of the modified resins depended on the polyarylate structure and concentration. The most effective modification of the cyanate ester resin could be attained because of the co‐continuous phase structure of the modified resin: 25 wt% inclusion of IPPA (50 mol% isophthalate units, weight average molecular weight (Mw) 38 500 g mol−1) led to a 130% increase in the fracture toughness (KIC) for the modified resin, with retention of its flexural properties and glass transition temperature, as compared with the values for the unmodified resin. Water absorptivity of the IPPA‐modified resin was smaller than that of the unmodified resin. Copyright © 2003 Society of Chemical Industry
Synthesis and reactivity of functionalized alkoxyamine initiators for nitroxide‐mediated radical polymerization of styrene
Authors: Li Irene Q , Knauss Daniel M , Priddy Duane B , Howell Bob A 
Published: April 2003

AbstractThe synthesis and examination of different functionalized (2,2,6,6‐tetramethyl‐1‐piperidinyloxy free radical) TEMPO‐containing alkoxyamine initiators for nitroxide‐mediated radical polymerization of styrene are reported. Initiators with ester and carbonate functional groups were synthesized by a low‐temperature radical‐abstraction reaction of the functionalized ethylbenzene in the presence of TEMPO to introduce the functional groups onto the initiating chain‐end of polystyrene. An initiator with two alkoxyamine groups symmetrically located at each end of a carbonate bond was also synthesized and used for nitroxide‐mediated styrene polymerization. Styrene polymerization using these initiators followed first‐order kinetics up to approximately 60 min at 140 °C or 30% monomer conversion. Alkoxyamines bearing an acetoxy or tert‐butylcarbonate group at the p‐position of 1‐(2,2,6,6‐tetramethyl‐1‐piperidinyloxy)ethylbenzene behave in a similar way to the unfunctionalized initiator. With an initiator containing two alkoxyamine groups, the resulting polymer molecular weight was twice that of the polymer obtained from initiators with only one alkoxyamine group, as expected from propagation from both chain‐ends. Upon hydrolysis of the carbonate bond, it was revealed that equivalent polymer chain growth occurred from each alkoxyamine site in the difunctional initiator. Copyright © 2003 Society of Chemical Industry
Stimuli‐responsive properties of aminophenylboronic acid‐carrying thermosensitive copolymers
Authors: Uğuzdoğan E , Kayı H , Denkbaş E B , Patır S , Tuncel A 
Published: April 2003

AbstractThermosensitive copolymers of N‐isopropylacrylamide (NIPA) and N‐acryloxysuccinimide (NASI) were obtained by solution polymerization using azobisisobutyronitrile as the initiator in a tetrahydrofuran–toluene mixture at 65 °C. A boronic acid‐carrying ligand, m‐aminophenylboronic acid (APBA) was covalently attached to the thermosensitive copolymer via the reaction between amino and succinimide groups. APBA‐coupled thermosensitive copolymer exhibited both temperature and pH sensitivity. Thermally reversible phase transitions were observed both in the acidic and alkaline pH region for the APBA‐modified copolymers obtained with different NASI feed concentrations. In our study, ribonucleic acid (RNA) was selected as a biomolecule having reactive groups which could potentially interact with the boronic acid functionality. The response of boronic acid‐carrying thermosensitive copolymer against RNA was investigated in aqueous media in the pH range 4–9. In the acidic pH region, an increase was observed in the lower critical solution temperature (LCST) of the APBA‐coupled thermosensitive copolymer with increasing RNA concentration. However, LCST decreased with increasing RNA concentration at both neutral and alkaline pH values. The LCST of the APBA‐attached copolymer varied linearly with the RNA concentration at pH of 3, 4 and 7.© 2003 Society of Chemical Industry