bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(N‐isopropylacrylamide). II. Effect of polymer concentration, temperature, and surfactant on the viscosity of aqueous solutions
Authors: Tam K. C. , Wu X. Y. , Pelton R. H. 
Published: April 2003

AbstractThe effects of polymer concentration, temperature, and surfactant on the rheological properties of poly(N‐isopropylacrylamide), poly NIPAM, were studied. Below 28°C the viscosity decreased with increasing temperature according to the Arrhenius expression. However, at 29°C the viscosity increased to a maximum value at 32°C, the lower critical solution temperature (LCST) for aqueous polyNIPAM. Higher temperatures gave a much lower viscosity. This unusual rheological behavior was explained by the phase behavior of the polymer. Sodium dodecyl sulfate (SDS) binding to polyNIPAM increased the cloud point temperature (CPT) and attenuated the unusual rheological behavior of polyNIPAM in water. © 1993 John Wiley & Sons, Inc.
Novel surface fixation technology of hydrogel based on photochemical method: Heparin‐immobilized hydrogelated surface
Authors: Nakayama Yasuhide , Matsuda Takehisa 
Published: April 2003

AbstractThis article reports a novel photoinduced surface process technology enabling simultaneous hydrogel formation and its surface fixation on polymeric substrates. The process consists of layering two different types of photoreactive coatings on a polymeric surface, an azidophenyl‐bearing polymer as an adhesive layer and cinnamoylated copolymer as a hydrogel layer, and subsequent UV irradiation. The photoreactive adhesive polymer coated on a substrate is poly(m‐azidostyrene), in which photoreaction of phenyl azido groups is responsible for the chemical bonding between the substrate and hydrogel. N,N‐dimethylacrylamide copolymer containing cinnamate moieties in their side chains, which undergo photocrosslinking via intermolecular dimerization, was applied as an overcoat on the adhesive layer. UV irradiation resulted in the formation of hydrogel chemically bonded onto the substrate. This was confirmed by ESCA measurements. A heparin‐immobilized hydrogelated surface with controlled release characteristics was demonstrated. © 1993 John Wiley & Sons, Inc.
Criteria for living systems with a special emphasis on living cationic polymerization of alkenes
Authors: Matyjaszewski Krzysztof 
Published: April 2003

AbstractA number of new living systems have been reported in recent years. Classic anionic polymerization of nonpolar monomers allows the synthesis of well‐defined high molecular weight polymers (DP > 1000), block copolymers, chains with perfect terminal functionalities and behaves as a true living system. Some new systems abuse the term “living polymerization.” A relatively modest criterion for living systems is proposed “3 X 10,000,” i.e., kp/kt > 104 mol‐1 L, kp/ktr > 104, 1/kt/tr > 104 s (translated to < 10% of chains deactivated at t ≈ 1000 s), which is related to a typical limit of the polymeric chain dimensions (DP ≈ 100) and standard synthetic manipulations (≈ 15 min). New living cationic systems are discussed in detail with special emphasis on exchange phenomena. © 1993 John Wiley & Sons, Inc.
Thermotropic copolyesters of a series of aromatic diols with phenylterephthalic acid and 4,4′‐oxybisbenzoic acid
Authors: Garay Raul O. , Bhowmik Pradip K. , Lenz Robert W. 
Published: April 2003

AbstractWholly aromatic, liquid crystalline, main chain copolyesters derived from various linearly substituted aromatic diols with mixtures of 2‐phenylterephthalic acid and a nonlinear aromatic dicarboxylic acid, 4,4′‐oxybisbenzoic acid, were prepared by acidolysis condensation polymerization reactions and characterized for their liquid crystalline properties. The formation of a liquid crystalline phase at elevated temperatures was not prevented by the introduction of up to 50 mol % of the nonlinear diacid in the copolymers, and all of those copolyesters exhibited nematic liquid crystalline phases. Furthermore, the inclusion of a nonlinear monomer was not as effective as was the presence of a phenyl substituent in decreasing the melting transition of these copolymers. All of the copolymers had high glass transition temperatures and high thermal stabilities. © 1993 John Wiley & Sons, Inc.
Polymerization of methyl methacrylate using isatoic anhydride–bromine donor–acceptor complex as the photoinitiator
Authors: Som Pranab Kumar , Banerjee Amar Nath 
Published: April 2003

AbstractIsatoic anhydride (IA) alone did not initiate photopolymerization of methyl metacrylate (MMA) at 40°C when exposed to visible light for about 180 min. But IA, when used in combination with bromine (Br2) as the initiator, initiated the photopolymerization of MMA readily under the same conditions. This behavior was explained by the formation of a donor‐acceptor type of complex between IA and Br2 in the presence of MMA. The polymerization was found to proceed via a free radical mechanism and the radical generation process was considered to follow an initial complexation reaction between the initiator components and monomer. The complex initiator showed nonideal kinetics for the present system (initiator exponent < 0.5) and was analyzed. The monomer exponents varied from 0.83 to 1.15 normally depending on the nature of solvent used. Initiator‐dependent chain termination was significant as well as the bimolecular mode of chain termination. © 1993 John Wiley & Sons, Inc.
Synthesis and characterization of aromatic polyesters with dicyanovinyl substituents
Authors: Kawatsuki Nobuhiro , Dörr Michael , Schmidt Hans‐Werner 
Published: April 2003

AbstractThe synthesis, characterization, and structure—property relations of aromatic polyesters with dicyanovinyl substituents is presented. Two comparable series of polyesters based on 3,4‐dihydroxybenzylidenemalononitrile and 3,4‐dihydroxy‐5‐methoxybenzylidenemalononitrile were prepared. As aromatic diacid components, terephthalic acid, phenylterephthalic acid, isophthalic acid, and 2‐phenylisophthalic acid were used. The polyesters were prepared by solution polycondensation. GPC investigations revealed the existence of substantial amounts of defined cyclic products. These cycles could be isolated by preparative GPC. The polyesters are soluble in common low boiling organic solvents, particularly the phenyl‐substituted ones. The polyesters are amorphous and have glass transition temperatures between 140 and 170°C. The absorption maxima are in the 306–322 nm range. The cut‐off wavelength is between 400 and 428 nm. The polyesters with methoxy substitutent have generally the absorptions at longer wavelength. The refractive index of thin films of these polyesters were between 1.61 and 1.63 at 632.8 nm. © 1993 John Wiley & Sons, Inc.
Cationic polymerization with p‐substituted benzyl p‐hydroxyphenyl methyl sulfonium salts: Effect of substituents and mechanistic aspects of initiation reaction
Authors: Hamazu Fumio , Akashi Sumio , Koizumi Tatsuya , Takata Toshikazu , Endo Takeshi 
Published: April 2003

AbstractVarious p‐substituted benzyl p‐hydroxyphenyl methyl sulfonium salts (2) were synthesized and their initiator activities were evaluated in bulk polymerization of glycidyl phenyl ether (PGE). The order of the activity was found to be 2b (X = CH3) > 2a (X = H) ≈ 2c (X = Cl) > 2d (X = NO2), indicating that the introduction of an electron‐donating group enhanced the activity. In Hammett's plots, the logarithm of the ratio of the polymerization rates (log kx/kH) was correlated with σ+ρ better than with σp and a negative ρ+ value (‐1.18) was obtained. Reaction of 2a with benzyl mercaptan mainly gave dibenzyl sulfide and p‐hydroxyphenyl methyl sulfide. The obtained results seemed to demonstrate that the OH group of the aryl group yielded no proton as initiator for the polymerization, whereas the benzyl group caused the polymerization, which was initiated by the corresponding benzyl cation formed by CS bond cleavage. © 1993 John Wiley & Sons, Inc.
Photopolymerization kinetics of oligo(ethylene oxide) and oligo(methylene) oxide dimethacrylates
Authors: Cook Wayne D. 
Published: April 2003

AbstractThe influence of temperature on the photopolymerization kinetics of oligo(methylene) oxide and oligo(ethylene oxide) dimethacrylate series has been investigated by isothermal DSC. The DSC curves showed a rapid rise in rate due to the Trommsdorff effect, and then a slow decline. A shoulder, apparent on many of the DSC curves at low conversions, became more prominent when the cure temperature was lowered. The kinetics were relatively insensitive to the dimethacrylate structure in the early stages of the reaction, but became more dependent as the reaction proceeded. A previously derived mathematical model, which allows for the influence of diffusion on the rate constants, was used to predict the kinetics. The dependence of the maximum rate and conversion on the curing temperature were adequately described by the model. The experimentally observed shoulder on the rate curve was also predicated as was the evolution of the rate/time curves with curing temperature. Similar predictions were found when a nonsteady state version of the model was used. The radiation intensity exponent varied from 0.3 to 0.6 possibly due to chain‐length effects and pseudo‐first order termination, respectively. The final degree of conversion increased with curing temperature (Tcure) and was correlated with the flexibility of the dimethacrylate. These data were fitted to a theoretical expression relating the final conversion to the resin Tg and to the Tcure. © 1993 John Wiley & Sons, Inc.
Kinetics and mechanism of electropolymerization of m‐aminophenol
Authors: Sankarapapavinasam S. 
Published: April 2003

AbstractThe kinetics and mechanism of electropolymerization of m‐aminophenol (mAP) has been investigated in acetonitrile (AN) and methanol (MeOH) media. The rate of polymerization is found to be proportional to [mAP] (current)0.5 at moderate current densities; at higher current densities, the rate of polymerization is independent of current density. A suitable mechanism has been proposed and the rate equation is derived to explain the observed factors. Rotating disc voltametry revealed that at low current densities, the rate of polymerization is charge controlled, while at high current densities it is diffusion controlled. The physicochemical characteristics of AN make it a better solvent than MeOH. © 1993 John Wiley & Sons, Inc.
Studies on the thermotropic liquid‐crystalline polymer. IX. Synthesis and properties of crosslinkable copoly(amide‐ester)s containing conjugated double bonds
Authors: Li Chen‐Hui , Cheng Hsin‐Pei , Chang Teh‐Chou , Chu Tsu‐Yao 
Published: April 2003

AbstractFour series of copoly(amide‐ester)s containing conjugated double bonds were prepared by using direct polycondensation in the presence of diphenylchlorophosphate (DPCP) and pyridine. Series I–III were prepared from para, meta‐aminophenol, or their mixture with p‐phenylene bis(acrylic acid) (PPBA), p‐carboxylic cinnamic acid (PCCA), and stilbenedicarboxylic acid (SDBA), respectively. Series IV was prepared from a mixture of aminophenols [2‐methyl 4‐aminophenol (MePAP) and m‐aminophenol (MAP)] with a mixture of diacids (PPBA and SDBA). Thermotropic liquid‐crystalline behavior of these polymers was studied by differential scanning calorimetry (DSC), and optical polarizing microscopy equipped with a heating stage. Series I, series II, and P40–P100 of series IV could undergo crosslinking reaction by heating. However, series III could undergo crosslinking reaction only by photoirradiation upon heating. After crosslinking reaction occurred, the properties of these polymers were also examined by DSC, TGA, WAXD, and IR. The synthesized polymers could be crosslinked in the liquid‐crystalline phase with retention of the order in the final crosslinked solid. © 1993 John Wiley & Sons, Inc.
Synthesis and properties of new polyesters having tetrahydrofuran rings in their main chains
Authors: Okada Masahiko , Aoi Keigo , Mizuno Wataru , Ito Shinji 
Published: April 2003

AbstractNew polyesters 6a–6c consisting of 2,4‐linked tetrahydrofuran rings were synthesized by bulk polycondensation of methyl trans‐ and cis‐4‐hydroxytetrahydrofuran‐2‐carboxylates (5a and 5b) and a stereoisomeric mixture of methyl 4‐hydroxy‐5‐methyltetrahydrofuran‐2‐carboxylate (5c) at high temperature. These monomers were prepared from methyl glycolate or methyl lactate and diethyl maleate through a four‐step reaction sequence. The polycondensation was carried out without solvent at different temperatures ranging from 150 to 220°C. Titanium isopropoxide was most effective among the catalysts examined, giving polyesters with number‐average molecular weights up to 2 × 104. Polyester 6a consisting of trans‐2,4‐linked tetrahydrofuran rings was soluble in trifluoroacetic acid and a mixed solvent of chloroform and methanol (10/1, v/v). Polyester 6b composed of cis‐2,4‐linked tetrahydrofuran rings was soluble in dimethyl sulfoxide and dimethylformamide in addition to the two solvents for 6a. Polyester 6c with 5‐methyl‐substituted tetrahydrofuran rings was composed of a mixture of stereoisomeric units and thus was soluble in a variety of solvents including chloroform, tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and dimethylformamide. The glass transition temperatures of 6a, 6b, and 6c determined by DSC were 109, 88, and 66°C. These polyesters were found to be very slowly hydrolyzed in a neutral phosphate buffer solution at ambient temperature. © 1993 John Wiley & Sons, Inc.
Cationic ring‐opening polymerization of 2‐isopropenyl‐4‐methylene‐1,3‐dioxolane
Authors: Park Jaekyeung , Yokozawa Tsutomu , Endo Takeshi 
Published: April 2003

AbstractPreparation and cationic ring‐opening polymerization of 2‐isopropenyl‐4‐methylene‐1,3‐dioxolane (VI) was performed. Unsaturated cyclic acetal VI was prepared by dehydrochlorination of 2‐isopropenyl‐4‐chloromethyl‐1,3‐dioxolane, which was easily obtained from methacrolein and epichlorohydrin, with sodium methoxide at ambient temperature. The cationic polymerization of VI with BF3OEt2 or CF3SO3H at −78°C afforded only crosslinked polymers, whereas the polymerization by CH3SO3H gave soluble poly(keto‐ether) which consisted of units VII containing an isopropenyl group in the side chain and units VIII containing a carbon‐carbon double bond in the main chain. The reaction of VI with ethanethiol in the presence of protic acid was also carried out as a model reaction of the polymerization. The reaction initiated by the addition of proton to the 4‐methylene group of VI, and quantitative ring‐opening isomerization followed by the addition of ethanethiol afforded acyclic ketone IX and X. On the basis of the model reaction, the polymerization mechanism is also discussed. © 1993 John Wiley & Sons, Inc.
A study of condensation of trithiane hexaoxide with formaldehyde
Authors: Jeczalik Jerzy 
Published: April 2003

AbstractThe title reaction catalyzed by NaOH in aqueous media was studied. The oligomeric products formed are characterized in terms of their yield, structure, etc. The effects of reaction parameters and media are also discussed. The reaction mechanism is proposed. © 1993 John Wiley & Sons, Inc.
Synthesis and photoconductivity study of phthalocyanine polymers. II. PVK‐co‐CuPc (COOH)3
Authors: Chen Hongzheng , Wang Mang , Feng Linxian , Yang Shilin 
Published: April 2003

AbstractCu‐phthalocyanine diimide (Cu‐diPc) was synthesized from a mixture of phthalic anhydride and pyromellitic dianhydride. By the hydrolysis of Cu‐diPc, Cu‐4,4′,5,5′‐tetracarboxy‐phthalocyanine (Cu‐taPc) was obtained. A novel polymer of polyvinylcarbazole‐bonded CuPc(COOH)3 (I) was synthesized by the Friedel–Crafts reaction of polyvinylcarbazole (PVK) with Cu‐phthalocyanine‐4,4′,5,5′‐tetraacid chloride. Polymer (I) contains ca. 5 mol % CuPc(COOH)3 rings, which are covalently bonded to PVK. Polymer (I) shows good photoconductivity, which is much better than that of the corresponding phthalocyanine monomers. The factors that influence the photoconductivity, such as the thickness of IFL, and the types and proportion of CTM, were also studied. © 1993 John Wiley & Sons, Inc.
Preparation and characterization of Co‐ and homopoly(phenylene etherimideketone)s
Authors: Parthiban A. , Sundaram N. 
Published: April 2003

AbstractPoly(phenylene etherimdeketone)s were prepared by Friedel–Crafts acylation type polymerization using P2O5CH3SO3H 1 : 10 (w/v) mixtures. Most of these polymers were semicrystalline. TgS ranged from 203 to 236°C and crystalline melt temperatures were observed between 306 and 435°C. All of the polymers exhibited high thermal stability and good solvent resistance. © 1993 John Wiley & Sons, Inc.
The conformational stability of tactic poly(2‐hydroxyethyl methacrylate) in aqueous salt solutions
Authors: Kang Seung Koo , Jhon Mu Shik 
Published: April 2003

AbstractThe conformational stability of tactic poly(2‐hydroxyethyl methacrylate) (PHEMA) in aqueous salt solutions was investigated by measurements of swelling, surface‐free energy, and differential scanning calorimetry, as this polymer in water is sensitive in various electrolytes. In the case of inorganic salts, the major role for the salt effect is played by the anions, and the exposure of hydrophobic components at the PHEMA surface can be correlated with the increase of the degree of swelling. The influence of cations is considerably weaker. In the case of organic salts, tetraalkylammonium halides cause the chain extension more effectively with the increase of alkyl chain length in the cations. This result indicates that the breakdown of the hydrophobic parts in PHEMA provides an important clue on conformational stability. The amount of water molecules bound with the hydrophilic sites of tactic‐PHEMA mainly depends on the chain extension and the hydration of cations. Since the sites in tactic‐PHEMA influenced by the cation and the anion are different, their effects cause the conformational transition at a specific range of salt concentration. © 1993 John Wiley & Sons, Inc.
Synthesis and characterization of polysiloxane–polyamide block and graft copolymers
Authors: Mougin N. , Rempp P. , Gnanou Y. 
Published: April 2003

AbstractThe synthesis of copolymers constituted of a central polydimethylsiloxane (PDMS) block flanked by two polyamide (PA) sequences is described. α, ω‐diacyllactam PDMS, when used as macroinitiator of lactam polymerization, gives rise to the expected triblock copolymer. Likewise, PDMS‐g‐PA graft copolymers are obtained from acyllactam containing polysiloxanes. NaAlH2(OCH2CH2OMe)2 turns out to be the best suited activating agent for the polymerization of ϵ‐caprolactam, in the experimental conditions required for the synthesis of polysiloxane–polyamide copolymers. The nucleophilic species formed by reaction of NaAlH2(OCH2CH2OMe)2 with ϵ‐caprolactam—2‐[bis(methoxyethoxy) aluminumoxy]‐1‐azacycloheptane sodium—is indeed nucleophilic enough to bring about the growth of PA chains and mild enough to stay inert towards PDMS. © 1993 John Wiley & Sons, Inc.
Bond interchange reactions in functionalized triglyceride oil/poly(ethylene terephthalate) compositions
Authors: Barrett L. W. , Ferguson G. S. , Sperling L. H. 
Published: April 2003

AbstractNaturally functionalized triglyceride oils are renewable resources which contain reactive chemical groups, hydroxyl in the case of castor oil, and epoxide in the case of vernonia oil. In this article, the reaction of these groups, and the ester linkages between the glycerol and acid residue portions of the oil molecule with poly(ethylene terephthalate) (PET) is investigated through a variety of means. Multiple reactions are possible in the triglyceride–PET system, some of which form a copolymer that increases miscibility, and if allowed to continue, forms a completely random copolymer mixture. Among the numerous reactions possible, PET–ester exchange with the hydroxyl or epoxide functionality of the triglyceride oils is found to be the most significant, and the effects of these and other reactions are observed and structural implications discussed. © 1993 John Wiley & Sons, Inc.
A new class of aromatic polyetheraroylhydrazides. I. Synthesis and chemical–physical characterization
Authors: Lanzetta N. , Malinconico M. , Martuscelli E. , Volpe M. G. 
Published: April 2003

AbstractA series of new aromatic polyetheraroylhydrazides incorporating 4‐oxybenzoyl units has been synthesized, whose general formula was [CONHNHCOOO–(CH2)xOphenyl O‐CONHNHCOO]n with x values in the range of 2 to 12. The increasing number of methylene units in the backbone gave rise to polymers which melted before the hydrazidic linkage underwent thermal cyclation to oxadiazole. Moreover, many polymers showed multiple endotherms on melting. X‐ray diffraction studies confirmed a crystalline organization of polyhydrazides for methylene units above 4. © 1993 John Wiley & Sons, Inc.
Synthesis and characterization of terminally carboxyl ethylene glycol monomethyl ethers‐substituted side‐chain liquid‐crystalline polysiloxanes
Authors: Chien Guo‐Ping Chang , Kuo Jen‐Feng , Chen Chuh‐Yung 
Published: April 2003

AbstractAlkene monomers containing phenyl or biphenyl carboxylate benzoate ester based on a mesogenic group of varied lengths of carboxyl oligo (ethanediol) monomethyl ethers as the terminal were synthesized. They were grafted onto poly(methyl‐hydrosiloxane) by the platinum‐catalyzed hydrosilylation process. The thermal transition temperatures and mesophase textures of monomers and of polymers were characterized by using differential scanning calorimetry (DSC), x‐ray diffraction, and polarized optical microscopy with a hot stage. The factors governing mesophase textures and thermal transition temperatures are discussed. © 1993 John Wiley & Sons, Inc.
The influence of microstructure and monomer properties on the erosion mechanism of a class of polyanhydrides
Authors: Göpferich Achim , Langer Robert 
Published: April 2003

AbstractThe erosion of three different polyanhydrides consisting of sebacic acid (SA) and 1,3‐bis(p‐carboxyphenoxy)propane (CPP) was investigated. Melt cast polymer matrices were prepared from the homopolymer p(SA) and two copolymers, p(CPP‐SA) 20 : 80 and p(CPP‐SA) 50 : 50. Particular attention was paid to the influence of the polymer matrix microstructure and of the monomers on erosion. Using polarized light microscopy we found that p(SA) and p(CPP‐SA) 20 : 80 matrices consist of spherulites. SEM investigations showed that their crystalline parts are more resistant to erosion than their amorphous areas. The matrices erode into highly porous devices, whose porosity is detectable by mercury porosimetry. Using wide‐angle x‐ray diffractometry we found that monomers crystallize inside the pores. DSC investigations showed a maximum of crystallized SA after 2–6 days and a continuous increase of CPP, which stays in the devices for weeks. We conclude that the microstructure and the monomer properties are the two main factors which determine the erosion of these polymers. The obtained data on changes in porosity, crystallinity, polymer matrix thickness, erosion front velocities, crystalline monomer content, and monomer release provides the basis for quantitatively describing the erosion process. © 1993 John Wiley & Sons, Inc.