bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of block copolymers from 2‐vinylnaphthalene by anionic polymerization
Authors: Zeng Faquan , Yang Mu , Zhang Jianxin , Varshney Sunil K. 
Published: November 2002

AbstractThe anionic polymerization of 2‐vinylnaphthalene (2VN) has been studied in tetrahydrofuran (THF) at −78 °C and in toluene at 40 °C. 2VN polymerization in THF, toluene, or toluene/THF (99:1 v/v) initiated by sec‐butyllithium (sBuLi) indicates living characteristics, affording polymers with predefined molecular weights and narrow molecular weight distributions. Block copolymers of 2VN with methyl methacrylate (MMA) and tert‐butyl acrylate (tBA) have been synthesized successfully by sequential monomer addition in THF at −78 °C initiated by an adduct of sBuLi–LiCl. The crossover propagation from poly(2‐vinylnaphthyllithium) (P2VN) macroanions to MMA and tBA appears to be living, the molecular weight and composition can be predicted, and the molecular weight distribution of the resulting block copolymer is narrow (weight‐average molecular/number‐average molecular weight < 1.3). Block copolymers with different chain lengths for the P2VN segment can easily be prepared by variations in the monomer ratios. The block copolymerization of 2VN with hexamethylcyclotrisiloxane also results in a block copolymer of P2VN and poly(dimethylsiloxane) (PDMS) contaminated with a significant amount of homo‐PDMS. Poly(2VN‐b‐nBA) (where nBA is n‐butyl acrylate) has also been prepared by the transesterification reaction of the poly(2VN‐b‐tBA) block copolymer. Size exclusion chromatography, Fourier transform infrared, and 1H NMR measurements indicate that the resulting polymers have the required architecture. The corresponding amphiphilic block copolymer of poly(2VN‐b‐AA) (where AA is acrylic acid) has been synthesized by acidic hydrolysis of the ester group of tert‐butyl from the poly(2VN‐b‐tBA) copolymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4387–4397, 2002
Preparation of a copolymer of methyl methacrylate with a new monomer, 2,2,6,6‐tetramethyl‐4‐benzyloxyl‐piperidinyl methacrylate, and its initiation of the graft copolymerization of styrene with a controlled radical mechanism
Authors: Zhang Haitao , Guo Zhenrong , Huang Junlian 
Published: November 2002

AbstractA copolymer [P(MMA‐co‐TBPM)] was prepared by the radical polymerization of methyl methacrylate (MMA) and 2,2,6,6‐tetramethyl‐4‐benzyloxyl‐piperidinyl methacrylate (TBPM) with azobisisobutyronitrile as an initiator. TBPM was a new monomer containing an activated ester. Both the copolymer and TBPM were characterized with NMR, IR, and gel permeation chromatography in detail. It was confirmed that P(MMA‐co‐TBPM) could initiate the graft polymerization of styrene by the cleavage of the activated ester of the TBPM segment. This process was controllable, and the molecular weight of the graft chain of polystyrene increased with the increment of conversion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4398–4403, 2002
Synthesis of a novel block copolymer poly(ethylene oxide)‐block‐poly(4‐vinylpyridine) by combination of anionic ring‐opening and controllable free‐radical polymerization
Authors: Lu Guangqiang , Jia Zhongfan , Yi Wen , Huang Junlian 
Published: November 2002

AbstractThe block copolymer poly(ethylene oxide)‐b‐poly(4‐vinylpyridine) was synthesized by a combination of living anionic ring‐opening polymerization and a controllable radical mechanism. The poly(ethylene oxide) prepolymer with the 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy end group (PEOT) was first obtained by anionic ring‐opening polymerization of ethylene oxide with sodium 4‐oxy‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy as the initiator in a homogeneous process. In the polymerization UV and electron spin resonance spectroscopy determined the 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy moiety was left intact. The copolymers were then obtained by radical polymerization of 4‐vinylpyridine in the presence of PEOT. The polymerization showed a controllable radical mechanism. The desired block copolymers were characterized by gel permeation chromatography, Fourier transform infrared, and NMR spectroscopy in detail. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4404–4409, 2002
SEC‐MALDI‐TOF mass spectral characterization of a hyperbranched polyether prepared via melt transetherification
Authors: Jayakannan M. , Van Dongen Joost L. J. , Behera Girish Ch. , Ramakrishnan S. 
Published: November 2002

AbstractAn AB2 monomer, 1‐(2‐hydroxyethoxy)‐3,5‐bis‐(methoxymethyl)‐2,4,6‐trimethylbenzene, was synthesized from mesitol and melt‐polycondensed in the presence of an acid catalyst via a transetherification process at 145–150 °C to yield a soluble, moderately high molecular weight hyperbranched polyether. The degree of branching in the polymer was calculated to be 0.78 by a comparison of its NMR spectrum with that of an appropriately designed model compound. The weight‐average molecular weight of the hyperbranched polymer was determined to be 64,600 (weight‐average molecular weight/number‐average molecular weight = 5.2) by size exclusion chromatography (SEC) in CHCl3 with polystyrene standards. The origin of the broad molecular weight distribution, which could either be intrinsic to such hyperbranched structures or be due to structural heterogeneity, was further probed by the fractionation of the samples by SEC and by the subjection of each fraction to matrix‐assisted laser desorption/ionization time‐of‐flight mass spectral analysis. The mass spectral analysis suggested the presence of two primary types of species: one corresponding to the simple branched structure and the other to macrocyclics. Interestingly, from the relative intensities of the two peaks, it was apparent that cyclization became favorable at higher conversions in the melt transetherification process. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4463–4476, 2002
Substituent effects on the chain‐transfer behavior of 7‐methylene‐2‐methyl‐1,5‐dithiacyclooctane in the presence of disulfides and thiols
Authors: Harrisson Simon , Davis Thomas P. , Evans Richard A. , Rizzardo Ezio 
Published: November 2002

AbstractThe chain‐transfer behavior of 7‐methylene‐2‐methyl‐1,5‐dithiacyclooctane was investigated in the presence of four chain‐transfer agents: thiophenol (PhSH), thiobenzoic acid (BzSH), diphenyl disulfide (PhSSPh), and dibenzoyl disulfide (BzSSBz). The chain‐transfer constants for these compounds at 60 °C were 0.38 (PhSH), 0.76 (BzSH), 0.24 (PhSSPh), and 0.05 (BzSSBz). The variations in the thiol chain‐transfer constants could be explained in terms of the stability of the resulting radicals. The chain transfer to the disulfides, however, appeared to be determined by the electronic character of the disulfide bond, and this suggests that the transfer took place via an addition–fragmentation mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4421–4425, 2002
Synthesis and characterization of novel luminescent polymers with alternate phenothiazine and divinylbenzene units
Authors: Wu Tzi‐Yi , Chen Yun 
Published: November 2002

AbstractNovel luminescent polymers (P1 and P2) carrying alternate phenothiazine and divinylbenzene units were synthesized via the Wittig reaction. Absorption, fluorescence, and cyclic voltammetric methods were applied to investigate their optical and electrochemical properties. The photoluminescence (PL) maxima of P1 and P2 were 559 and 568 nm, respectively. Compared with reported hole‐transport groups such as carbazole, alkyldiphenylamine, triphenylamine, and iminodibenzyl chromophores, phenothiazine moieties in P1 and P2 bathochromically shift the PL maxima and narrow the band gaps. Their relative PL efficiencies were about 0.5 and 0.3 in solution and in the film state, respectively. Moreover, highest occupied molecular orbitals of P1 (4.78 eV) and P2 (4.74 eV) were even higher than the work function of ITO electrode (4.8 eV). The threshold electric fields of the Al/P1 (or P2)/ITO device were about 1.52–1.63 · 106 V/cm, which were smaller than 1.73 · 106 V/cm of P3, consisting of alternate iminodibenzyl and divinylbenzene units. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4452–4462, 2002
Kinetic study of the nitroxide‐mediated controlled free‐radical polymerization of n‐butyl acrylate in aqueous miniemulsions
Authors: Farcet Céline , Nicolas Julien , Charleux Bernadette 
Published: November 2002

AbstractThe controlled free‐radical homopolymerization of n‐butyl acrylate was studied in aqueous miniemulsions at 112 and 125 °C with a low molar mass alkoxyamine unimolecular initiator and an acyclic β‐phosphonylated nitroxide mediator, N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl) nitroxide, also called SG1. The polymerizations led to stable latices with 20 wt % solids and were obtained with neither coagulation during synthesis nor destabilization over time. However, in contrast to latices obtained via classical free‐radical polymerization, the average particle size of the final latices was large, with broad particle size distributions. The initial [SG1]0/[alkoxyamine]0 molar ratio was shown to control the rate of polymerization. The fraction of SG1 released upon macroradical self‐termination was small with respect to the initial alkoxyamine concentration, indicating a very low fraction of dead chains. Average molar masses were controlled by the initial concentration of alkoxyamine and increased linearly with monomer conversion. The molar mass distribution was narrow, depending on the initial concentration of free nitroxide in the system. The initiator efficiency was lower than 1 at 112 °C but was very significantly improved when either a macroinitiator was used at 112 °C or the polymerization temperature was raised to 125 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4410–4420, 2002
Star polymer synthesis using trithiocarbonate functional β‐cyclodextrin cores (reversible addition–fragmentation chain‐transfer polymerization)
Authors: Stenzel Martina H. , Davis Thomas P. 
Published: November 2002

AbstractPolystyrene stars were synthesized with reversible addition–fragmentation chain‐transfer (RAFT) polymerization. The core of the stars comprised a trithiocarbonate heptafunctional β‐cyclodextrin ring. Polymerizations were performed at 100 and 120 °C in the absence of an extraneous initiator and at 60 °C in the presence of a radical initiator. Monofunctional trithiocarbonate was also synthesized and used to make linear polystyrene to allow direct a comparison with the star synthesis. In all cases, the polymerization kinetics conformed to pseudo‐first‐order behavior. The measured molecular weights of the stars were found to deviate from those predicted on the basis of the monomer/trithiocarbonate group ratio. The extent of this deviation was dependent on the polymerization temperature, RAFT agent concentration, and conversion. Despite the low radical concentrations, termination reactions are suggested to play a significant role in the seven‐arm polystyrene star syntheses. The synthetic method was found to be suitable for generating star block structures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4498–4512, 2002
Telomerization of vinylidene fluoride with alkyl (or aryl) trifluoromethanethiosulfonates
Authors: Ameduri Bruno , Billard Thierry , Langlois Bernard 
Published: November 2002

AbstractThe photochemical‐induced telomerization of vinylidene fluoride (VDF) with cyclohexyl (or phenyl) trifluoromethanethiosulfonate (CF3SO2SR), leading to CF3(VDF)nSR telomers, where R stands for cyclohexyl or phenyl, is presented. These sulfurated transfer agents were synthesized by the reaction between sodium triflinate (CF3SO2Na) and disulfide in the presence of bromine. 19F NMR spectroscopy enabled an assessment of the average degrees of telomerization (DPn) of these telomers with a neat CF3 end group as the label. These DPn values increased for higher [VDF]0/[CF3SO2SR]0 initial molar ratios. Interestingly, the normal/reversed ratio of VDF units in these telomers was low. Finally, the cotelomerization of VDF and hexafluoropropylene with these transfer agents was successfully achieved, leading to original ω‐CF3 fluoroelastomers, the thermal properties of which were investigated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4538–4549, 2002
Micellar polymerization of amphiphilic poly(vinyl alcohol) macromonomer having a methacrylate end group prepared by aldol‐type group‐transfer polymerization
Authors: Takasu Akinori , Ohmori Shigeki , Yamauchi Yutaka , Hirabayashi Tadamichi 
Published: November 2002

AbstractAmphiphilic and heterotactic‐rich poly(vinyl alcohol) (PVA) macromonomer, that is, PVA having a phenyl or phenoxyethyl methacrylate unit as the polymerizable end group, was synthesized via the aldol‐type group‐transfer polymerization (aldol‐GTP) technique. Aldol‐GTPs of vinyloxytriethylsilane (VOTES) were carried out in dichloromethane with 4‐methacryloylbenzaldehyde and 4‐(2‐methacryloylethoxy)benzaldehyde as the initiators with various Lewis acids. The polymerizations proceeded smoothly to give silylated PVA macromonomers (number‐average molecular weights: 1.3 × 103–1.96 × 104). Poly(VOTES) was easily desilylated to give heterotactic‐rich PVA macromonomer in good yield. The critical micelle concentration of the PVA macromonomer was determined by surface‐tension measurement. Micellar polymerization of the amphiphilic macromonomer gave comb‐shaped (graft) polymer having PVA side chains effectively (conversion: 80–82%), whereas polymerization in dimethyl sulfoxide (homogeneous state) did not. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4477–4484, 2002
Biodegradable network elastomeric polyesters from multifunctional aromatic carboxylic acids and poly(ϵ‐caprolactone) diols
Authors: Nagata Minoru , Kanechika Masao , Sakai Wataru , Tsutsumi Naoto 
Published: November 2002

AbstractNovel biodegradable network polyesters were prepared from multifunctional aromatic carboxylic acids [trimesic acid (Y), pyromellic acid (X), and mellic acid (YM)] and poly(ϵ‐caprolactone) (PCL) diols with molecular weights of 530, 1250, and 2000. Prepolymers prepared by a melt polycondensation method were cast from dimethylformamide solutions and postpolymerized at 220 °C for various times to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyesters obtained were characterized by infrared absorption spectra, wide‐angle X‐ray diffraction analysis, density measurements, differential scanning calorimetry, thermomechanical analysis, and tensile testing. Some network polyester films, including YPCL1250, XPCL1250, and YMPCL2000, showed elastomeric properties with high ultimate elongation and low tensile modulus. The enzymatic degradation was measured by the weight loss of the network polyester films in a buffer solution with Rhizopus delemar lipase at 37 °C. The degree and rate of degradation increased with the increasing molecular weight of the PCL diols, but they decreased in the order of YPCL > XPCL > YMPCL because of the increase in the crosslinking densities of the network films. The degraded products after enzymatic degradation showed that the ester linkage of the PCL component and the aromatic ester linkage between Y and PCL diols were hydrolyzed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4523–4529, 2002
Attempt to investigate the temperature effect on polycondensation from the solution copolyesterification of preformed oligomers and bisphenols with tosyl chloride/dimethylformamide/pyridine
Authors: Higashi Fukuji , Hayashi Ryohsuke , Ohno Harumi 
Published: November 2002

AbstractTwo‐stage copolycondensations of isophthalic acid/terephthalic acid (50/50) and a bisphenol (BP) first and then a comonomer BP were carried at 80 and 120 °C. BPs were divided into two groups: those with polar substituents and those without polar substituents. The copolycondensation with any combination of BPs proceeded nearly equally well at 80 °C. However, the reaction at 120 °C was retarded differently by the groups of comonomers. For the preformed oligomers from BPs without polar substituents, the temperature did not affect the reaction very much, but the reaction was significantly retarded with BPs containing polar groups. All of the reactions of the oligomers from BPs having polar groups with comonomer BPs, regardless of their substituents, were greatly disturbed by the temperature rising. The results were attributed to the temperature effect on the way in which the oligomers reacted with comonomers due to the interactions between them, and they were examined in terms of the distributions of comonomers determined by 1H NMR. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4556–4562, 2002
Synthesis and optical and electrochemical properties of novel copolymers containing alternating 2,3‐divinylquinoxaline and hole‐transporting units
Authors: Wu Tzi‐Yi , Chen Yun 
Published: November 2002

AbstractFor the enhancement of charge affinity, electron‐affinitive 2,3‐divinylquinoxaline and a series of hole‐transporting chromophores (iminodibenzyl, phenothiazine, dihexyloxybenzene, and didodecyloxydistyrylbenzene) were incorporated alternately into the polymeric main chain. The resulting copolymers (P1–P4) were basically amorphous materials and were thermally stable below 300 °C. The electronic structures, photoluminescence, and electrochemical properties of these copolymers were mainly determined by the electron‐donating chromophores in the backbone. They showed significant positive solvatochromism in formic acid. An electrochemical study revealed that they exhibited lower band gaps (<2.3 eV) due to alternating donor and acceptor conjugated units (push–pull structure). Single‐layer light‐emitting diodes of aluminum, P1–P4, and indium tin oxide glass were fabricated, and preliminary electroluminescence spectra showed that P1, P3, and P4 were orange‐emitting materials. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4570–4580, 2002
Alternating copolymerization of propylene oxide with carbon monoxide catalyzed by Co complex and Co/Ru complexes
Authors: Takeuchi Daisuke , Sakaguchi Yoshihiko , Osakada Kohtaro 
Published: November 2002

AbstractCo2(CO)8 catalyzes the ring‐opening copolymerization of propylene oxide with CO to afford the polyester in the presence of various amine cocatalysts. The 1H and 13C{1H} NMR spectra of the polyester, obtained by the Co2(CO)8–3‐hydroxypyridine catalyst, show the following structure [CH2CH(CH3)OCO]n. The Co2(CO)8–phenol catalyst gives the polyester, which contains the partial structural unit formed through the ring‐opening copolymerization of tetrahydrofuran with CO. The bidentate amines, such as bipyridine and N,N,N′,N′‐tetramethylethylenediamine, enhance the Co complex‐catalyzed copolymerization, which produces the polyester with a regulated structure. Acylcobalt complexes, (RCO)Co(CO)n (R = Me or CH2Ph), prepared in situ, do not catalyze the copolymerization even in the presence of pyridine. This suggests that the chain growth involves the intermolecular nucleophilic addition of the OH group of the intermediate complex to the acyl–cobalt bond, forming an ester bond rather than the insertion of propylene oxide into the acyl–cobalt bond. Co2(CO)8Ru3(CO)12 mixtures also bring about the copolymerization of propylene oxide with CO. The molar ratio of Ru to Co affects the yield, molecular weight, and structure of the produced copolymer. The catalysis is ascribed to the RuCo mixed‐metal cluster formed in the reaction mixture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4530–4537, 2002
Synthesis and characterization of novel biodegradable poly(ester amide) with ether linkage in the backbone chain
Authors: Li Ming Xia , Zhuo Ren Xi , Qu Fan Qi 
Published: November 2002

AbstractA series of biodegradable poly(ester amide)s having ether linkages in the main chain were synthesized by ring‐opening copolymerization of 3‐morpholinone (M) and ε‐caprolactone (CL) in bulk with stannous octoate, aluminium isopropoxide, or aluminium isobutoxide as an initiator. The influence of reaction conditions such as polymerization temperature, polymerization time, initiator, and initiator concentration on the monomer conversion and molecular weight are investigated. The comonomer reactivity ratios were determined (M 0.74 and CL 1.28). The water absorption of the polymers increased with increasing M content. In vitro degradation data and the release profiles of 5‐Fluorouracil showed that both the degradation rate and drug‐release rate increase with an enhanced M content in the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4550–4555, 2002
Displaying images on mobile devices: capabilities, issues, and solutions
Authors: Luo Jiebo , Singhal Amit , Braun Gustav , Gray Robert T. , Touchard Nicolas , Seignol Olivier 
Published: November 2002

AbstractWireless imaging is enabling visual communication ‘anytime anywhere’ to become a reality. Apart from wireless communication issues, a key technical challenge is how to achieve the best‐perceived image quality given the limited screen size and display bit‐depth of the mobile devices. In this paper, we give an overview of the current capabilities of various mobile devices, highlight some of the technical issues, and present potential solutions. In addition, we present a review of some of the software products on the market and look ahead to the trend toward more capable devices. Copyright © 2002 John Wiley & Sons, Ltd.
Second‐generation error concealment for video transport over error‐prone channels
Authors: Chen Trista Pei‐chun , Chen Tsuhan 
Published: November 2002

AbstractVideo transport over error‐prone channels may result in loss or erroneous decoding of the video data. Error concealment is an effective mechanism to reconstruct the video data. In this paper, we review error‐concealment methods and introduce a new framework, which we refer to assecond‐generation error concealment. All the error‐concealment methods reconstruct the lost video data by making use of certaina prioriknowledge about the video content.First‐generation error concealmentbuilds sucha prioriin a heuristic manner. The proposed second‐generation error concealment builds thea prioriby modeling the statistics of the video content explicitly, typically in the region of interest (ROI). Context‐based models are trained with the correctly received video data and then used to replenish the lost video data. Trained models capture the statistics of the video content and thus reconstruct the lost video data better than reconstruction by heuristics. A new dynamic model ‘updating principal components’ (UPC) is proposed as a model for second‐generation error concealment. UPC can be applied to pixel values to conceal loss of pixel data. In addition, UPC can be applied to motion vectors, which results in ‘updating eigenflows’ (U‐Eigenflow), to conceal loss of motion vectors. With UPC applied to both pixel values and motion vectors, hybrid temporal/spatial error concealment can be achieved. The proposed second‐generation error‐concealment method provides superior performances to first‐generation error‐concealment methods. Copyright © 2002 John Wiley & Sons, Ltd.
3G wireless multimedia: technologies and practical issues
Authors: Zeng Wenjun , Wen Jiangtao 
Published: November 2002

AbstractThis paper provides overviews of the emerging wireless communication standards, end‐to‐end wireless streaming systems, and relevant wireless multimedia technologies. It highlights some of the challenges in the deployment of 3G wireless multimedia services, using PacketVideo's solutions as an example. Copyright © 2002 John Wiley & Sons, Ltd.