bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of a melt processable liquid crystal copolyester
Authors: Thammongkol Vivan , Warner Steven B. , Polk Malcolm B. 
Published: April 2003

AbstractPoly[oxy(2‐methyl‐1,4‐phenylene)oxyterephthaloyl‐co‐oxymethylene‐1,4‐cyclohexylene‐methyleneoxyterephthaloyl] was synthesized using a solution‐based process. This copolyester has cyclohexylene dimethylene as a semi‐rigid spacer along the polymer main chain to interrupt the inherent rigidity of the system while preserving the mesogenicity of the macromolecules. Polymer characterization includes elemental analysis, Fourier transform infrared spectroscopy, nuclear magnetic resonance, hot‐stage polarized light microscopy, wide‐angle x‐ray diffraction, dilute solution viscometry, differential scanning calorimetry, and thermogravimetric analysis. This copolyester shows nematic liquid crystalline behavior in polarized light above about 240°C. The intrinsic and inherent viscosities are 0.88 and 0.68 dL/g respectively. The observed melting temperature of this copolyester is about 265°C, but melting begins as low as 215°C, making the polymer readily melt‐processable. The degradation temperature is about 340°C under a nitrogen atmosphere. © 1995 John Wiley & Sons, Inc.
Wholly aromatic thermotropic liquid crystalline polyesters of 4,4′‐biphenol, substituted biphenols, and 1,1′‐binaphthyl‐4,4′‐diol with 3,4′‐benzophenone dicarboxylic acid
Authors: Han Haesook , Bhowmik Pradip K. 
Published: April 2003

AbstractWholly aromatic, thermotropic homopolyesters, derived from 4,4′‐biphenol, substituted biphenols, or 1,1′‐binaphthyl‐4,4′‐diol and 3,4′‐benzophenone dicarboxylic acid, and two copolyesters, each of which contained 30 mol % of 6‐hydroxy‐2‐naphthoic acid, were prepared by acidolysis polycondensation reactions and characterized for their liquid crystalline properties. The solubility behavior of these polymers has also been investigated. The two homopolymers of phenyl‐substituted biphenols with 3,4′‐benzophenone dicarboxylic acid were soluble in many common organic solvents. All of the homopolymers had lower Tm/Tf values than those with terephthalic acid, which was attributed to the incorporation of the asymmetric 3,4′‐benzophenone dicarboxylate units in a head‐to‐head and head‐to‐tail fashion along the polyester chain. Two copolymers had lower Tm values than those of the respective homopolymers, as expected. They formed nematic phases which persisted up to 400°C, except those of phenyl‐substituted biphenols with 3,4′‐benzophenone dicarboxylic acid. Each of these two polymers also exhibited an accessible Ti transition, and had a broad range of LC phase. They had glass transition temperatures, Tg, in the range of 139‐209°C and high thermal stabilities in the temperature range of 465‐511°C. © 1995 John Wiley & Sons, Inc.
Microgel formation in the free radical crosslinking polymerization of ethylene glycol dimethacrylate (EGDMA). I. Experimental
Authors: Chiu Y. Y. , Lee L. James 
Published: April 2003

AbstractAn important feature of free radical crosslinking polymerization of ethylene glycol dimethacrylate (EGDMA) resin is the formation of heterogeneous structure through intramolecular reaction. Such structure formation affects not only the cure behavior and rheological changes of the resin but also the physical properties of the formed polymers. In this study, the reaction kinetics, morphological changes, and characteristics of formed polymers were examined by a differential scanning calorimeter, a Rheometrics Dynamic Analyzer, a dynamic light scattering goniometer, and a Fourier transfer infrared spectrometer. Experimental data showed the formation of bimodal polymers before gelation. These polymers are partially crosslinked and can be considered as microgel particles. © 1995 John Wiley & Sons, Inc.
Polymerization of 1‐ethynylcyclohexene by tungsten and molybdenum‐based catalysts
Authors: Gal Yeong‐Soon , Jung Bal , Kim Ji‐Heung , Lee Won‐Chul , Choi Sam‐Kwon 
Published: April 2003

Abstract1‐Ethynylcyclohexene, an acetylene derivative having cyclohexenyl substituent, was polymerized by various W‐ and Mo‐based catalysts. WCl6‐EtAlCl2 catalyst system was found to be very effective for this polymerization. The effects of the monomer‐to‐catalyst mol ratio, the initial monomer concentration, the temperature, and the cocatalysts for the polymerization of 1‐ethynylcyclohexene by WCl6 were investigated. The catalytic activity of Mo‐based catalysts was found to be similar to that of W‐based catalysts. The polymer structure was identified to have a conjugated polymer backbone carrying a cyclohexenyl substituent. The resulting polymers were light‐brown powder and completely soluble in aromatic and halogenated hydrocarbon solvents such as chlorobenzene, benzene, chloroform, carbon tetrachloride, etc. Studies of the thermal properties and morphology of poly(1‐ethynylcyclohexene) were also carried out. © 1995 John Wiley & Sons, Inc.
Cyanated liquid crystals withtrans‐stilbene structure: Syntheses and their cyclotrimerizations
Authors: Ou Jiunn–Chih , Hong Yen–Long , Yen Fu–Shan , Hong Jin–Long 
Published: April 2003

AbstractLiquid crystalline aromatic monocyanate (M) and dicyanates (D1andD2) withtrans‐stilbene (PhCHCHPh) structure were synthesized and their cyclotrimerization reactions were studied by differential scanning calorimetry and infrared spectroscopy. MonocyanateMunderwent cyclotrimerization to yield a trimerized material with discotic properties. DicyanateD2and its cured product failed to exhibit any mesophase. In contrast, polycyclotrimerization of dicyanateD1obtained a liquid crystalline thermoset with its schlieren texture prolonged over a wide temperature range. © 1995 John Wiley & Sons, Inc.
Peroxide generation and decomposition on polymer surface
Authors: Kulik Eduard A. , Ivanchenko Maria I. , Kato Koichi , Sano Shushi , Ikada Yoshito 
Published: April 2003

AbstractPolymer peroxides were generated onto polypropylene and polyurethane films, and polyester fibers by ozonization, UV irradiation, and plasma treatment. Their thermal and redox decompositions were studied using two assays: peroxidase and iodide. They may differ in the sensitivity to access the peroxides, depending on their localization in the polymer substrates. It was found that the generated peroxides are likely to be distributed not only on the outermost surface, but also in the subsurface of the polymer substrates. Plasma treatment provided polyurethane film with easily accessible peroxides, while UV irradiation and ozonization generated peroxides that were mostly incapable of reacting with aqueous solution of peroxidase. Redox decomposition of the peroxide groups by ferrous ions at 25°C showed that less than 50% of peroxides could react with ferrous ions with a rate constant similar to that of hydrogen peroxide in aqueous solution. Thermal decomposition of the peroxides did not obey the first‐order kinetics, probably due to formation of not single peroxide species with different decomposition rate constants. The lowest decomposition rate constant observed at 65°C was 3 × 10−3 min−1, which did not depend on the polymer substrate nature and the method of peroxide generation. © 1995 John Wiley & Sons, Inc.
Synthesis of high molecular weight poly(ether ketone)s by polycondensation of activated bis(aryl chloride)s with bisphenolates
Authors: Percec V. , Grigoras M. , Clough R. S. , Fanjul J. 
Published: April 2003

AbstractThe ability to achieve high molecular weight poly(ether ketone)s from the polycondensation of bis(aryl chloride)s with bis(phenolate)s has been consistently demonstrated. The polymerizations presented here help to delineate for specific bis(aryl chloride)/bisphenolate pairs the reaction conditions required to obtain high molecular weight polymers. Polycondensation of 1,3‐bis(4‐chlorobenzoyl)‐5‐tert‐butylbenzene (6) and 2,2′‐bis(4‐chlorobenzoyl)‐biphenyl (15) with various bisphenolates as well as of 2,2′‐bis(4‐hydroxyphenoxy)biphenyl (33) with 4,4′‐dichlorobenzophenone (41) and 1,3‐bis(4‐chlorobenzoyl)benzene (43) were used as representative model systems to select reaction conditions that led to high molecular weight polymers. © 1995 John Wiley & Sons, Inc.
Reactions on polymers with amine groups. I. Reactions of vinylpridine polymers and of their model compounds with unsaturated carboxylic acids
Authors: Bărboiu Virgil , Streba Emilia , Luca Cornelia , Simionescu Cristofor I. 
Published: April 2003

AbstractThe reactions of vinylpyridine polymers with α,β‐unsaturated carboxylic acids such as acrylic, methacrylic, crotonic, itaconic, cinnamic, fumaric, and maleic acids were studied. It was found that, when reacted with acrylic, itaconic and fumaric acids. poly(4‐vinylpyridine) gave macromolecular betaine products while with maleic acid, betaine as well as the corresponding salt was obtained. Poly(2‐vinylpyridine) reacted with the same acids as poly(4‐vinylpyridine) gave only the salts. No significant changes were observed with the two polymers when reacted with methacrylic, crotonic, and cinnamic acids. To attempt to rationalize these observations with the two macromolecular tertiary amines, the reactions of 4‐methyl and 2‐methylpyridines with the same carboxylic acids were investigated. The 1H‐NMR methodology was generally applied to elucidate the chemical structure obtained. © 1995 John Wiley & Sons, Inc.
Blends of bisphenol a polycarbonate and acrylic polymers. I. A chemical reaction mechanism
Authors: Debier D. , Devaux J. , Legras R. 
Published: April 2003

AbstractThe chemical reaction at high temperature (above 200°C) between PC and PMMA has been very recently highlighted. However, no clear reaction mechanism has been proposed to explain this phenomenon. We suggest a reaction mechanism following two steps. The first step consists of hydrolysis of the ester bonds of the PMMA leading to acid pendant groups. These acids can then either ring close into glutaric anhydride, or acidolyze the carbonate bonds of PC during the second step. At the same time, benzoic acid produced by PC degradation could further react with PMMA or acidolyze the carbonate groups leading to the crosslinking of the system. A satisfactory contact between the reacting units is a key point in the proces. Significant amounts of PC‐PMMA copolymer are obtained when the reaction is performed from a miscible system. On the contrary, no reaction occurs during melt mixing. Understanding the process enables us to specify the conditions, in which no chemical reaction takes place. In nonreactive conditions, PC/PMMA blends remain immiscible for several hours at 300°C. The thermodynamic UCST proposed in the literature is just an artifact due to the occurrence of the chemical reaction. © 1995 John Wiley & Sons, Inc.
Fully aromatic thermotropic liquid crystalline polyesters of 3‐phenyl‐4,4′‐biphenol with 4,4′‐benzophenone dicarboxylic acid
Authors: Bhowmik Pradip K. , Han Haesook 
Published: April 2003

AbstractA series of fully aromatic, thermotropic polyesters, derived from 3‐phenyl‐4,4′‐biphenol (MPBP), nonlinear 4,4′‐benzophenone dicarboxylic acid (4,4′‐BDA), and various other comonomers was prepared by the melt polycondensation method and characterized for their thermotropic liquid crystalline behavior by a variety of experimental techniques. The homopolymer of MPBP with 4,4′‐BDA had a fusion temperature (Tf) at 240°C, exhibited a nematic liquid crystalline phase, and had a narrow liquid crystalline range of 60°C. All of the copolyesters of MPBP with 4,4′‐BDA and either 30 mol % 4‐hydroxybenzoic acid (HBA), 6‐hydroxy‐2‐naphthoic acid (HNA) or 50 mol % terephthalic acid (TA), 2,6‐naphthale‐nedicarboxylic acid (2,6‐NDA) and low Tf values in the range of 210–230°C, exhibited a nematic phase, and had accessible isotropization transitions (Ti) in the range of 320–420°C, respectively. As expected, each of them had a broader range of liquid crystalline phase than the homopolymer. They had a “frozen” nematic, glassy order as determined with the wide‐angle X‐ray diffraction (WAXD) studies. The morphology of each of the “as‐made” polyesters had a fibrous structure as determined with the scanning electron microscopy (SEM), which arises because of the liquid crystalline domains. Moreover, they had higher glass transition temperatures (Tg) in the range of 167–190°C than those of other liquid crystalline polyesters, and excellent thermal stabilities (Td) in the range of 500–533°C, respectively. © 1995 John Wiley & Sons, Inc.
Differences in structure growth in amine curing of diglycidyl ether of bisphenol a and N,N‐diglycidylaniline epoxy resins: Bifunctional models
Authors: Matĕjka Libor , Podzimek S̆tĕpán , Dus̆ek Karel 
Published: April 2003

AbstractThe reaction of diepoxides, diglycidylaniline (DGA), or diglycidyl ether of Bisphenol A (DGEBA) with aniline was followed using HPLC and SEC. The effect of molar ratio of reagents, dilution of the system, reaction temperature, and the difference between the reaction mechanisms for DGA and DGEBA systems on the reaction kinetics and molecular weight evolution is discussed. Molecular weights of the DGA‐aniline polymers were by an order of magnitude lower than those of the DGEBA‐aniline polymers due to the formation of small cyclic products in the former case. Also, a reduction in Mn with increasing temperature, dilution, and diluent polarity is brought about by a greater tendency toward cyclization under these conditions. Theoretically calculated molecular weight evolution during the reaction is in satisfactory agreement with the experiment. © 1995 John Wiley & Sons, Inc.
Effect of methyl groups on the thermal properties of polyesters from methyl substituted 1,4‐butanediols and 4,4′‐biphenyldicarboxylic acid
Authors: Loman Albert J. B. , van der Does Leen , Bantjes Adriaan , Vulic Ivan 
Published: April 2003

AbstractResults are reported on the effect of lateral methyl groups on the thermal properties of a series of polyesters prepared from diethyl 4,4′‐biphenyldicarboxylate and various methyl substituted 1,4‐butanediols. The diols were 1,4‐butanediol; 2‐methyl‐1,4‐butanediol; 2,2‐dimethyl‐1,4‐butanediol; 2,3‐dimethyl‐1,4‐butanediol; 2,2,3‐trimethyl‐1,4‐butanediol; and 2,2,3,3‐tetramethyl‐1,4‐butanediol. Apart from the tetramethyl derivatve, the transition temperatures of the methyl substituted polyesters were lower with respect of the unsubstituted polyester. On the basis of polarized photomicrographs, a smectic A mesophase was found for the unsubstituted polyester, whereas a nematic mesophase was observed for the 2‐methyl substituted polyster. The 2,2‐dimethyl, 2,3‐dimethyl, and the 2,2,3‐trimethyl substituted polyesters showed no liquid crystalline behavior. The 2,2,3,3‐tetramethyl derivative displayed a birefringent melt phase although the DSC measurements were not unambiguous. A copolyester based on diethyl 4,4′‐biphenyldicarboxylate, 1,4‐butanediol, and 2,2,3,3‐tetramethyl‐1,4‐butanediol showed a broad nematic mesophase. Further evidence for the nematic mesophase of this copolyester and the 2‐methyl substituted polyester was provided by dynamic rheological experiments. Based on thermogravimetric analysis, it was concluded that the thermal stability was affected only when four methyl side groups were present in the spacer. © 1995 John Wiley & Sons, Inc.
Deep UV photoresists based on poly(dl‐tert‐butyl fumarate)
Authors: Crivello J. V. , Shim S.‐Y. 
Published: April 2003

AbstractPoly(di‐tert‐butyl fumarate) was prepared and evaluated as a potential candidate as a deep UV photoresist. Although this polymer displayed excellent sensitivity, the polymer was found to exhibit poor dry etch resistance. Copolymers of di‐tert‐butyl fumarate with either allyltrimethylsilane or styrene, and an onium salt as a photoacid generator were synthesized and subsequently evaluated using a 248‐nm KrF excimer laser step‐and‐repeat system (stepper). At 248 nm, the absorbance of ∼ 1 μm thick resist films was only 0.156‐0.211. The sensitivities of these resists were 1‐4 mJ/cm2. The dry etch resistance of these photoresists was comparable to that of conventional positive photoresists based on novolac resins. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of poly[2,5‐bis(triethoxy)‐1,4‐phenylene vinylene]
Authors: Garay Raul O. , Mayer Bernd , Karasz Frank E. , Lenz Robert W. 
Published: April 2003

AbstractThe synthesis of a highly soluble, 2,5‐disubstituted poly(p‐phenylene vinylene) with pendant side chains containing ether groups was accomplished by a dehydrochlorination route. Specific interactions of the oxygen‐containing side chains with the solvent are presumably responsible for the high solubility of the polymer, especially in protogenic solvents. The polymer microstructure was characterized by 1H‐ and 13C‐NMR. The polymer showed solvatochromic properties when dissolved in a variety of solvents. The relatively high molecular weight (Mn = 17,000) permitted the fabrication of free‐standing films. The electrical conductivity of iodine‐doped films was approximately 2 × 10–2 S cm–1. © 1995 John Wiley & Sons, Inc.
Structure/Reactivity relationships for high‐performance polyamides: Kinetics of the reactions of N,N′‐dihexylphthalamides in the presence of added copper iodide and water
Authors: Broadbelt Linda J. , Klein Michael T. , Dean Barry D. , Andrews Stephen M. 
Published: April 2003

AbstractAn experimental study to determine the effect of copper(I) iodide and water on the rate and product distribution of aliphatic‐aromatic polyamide degradation was carried out by using N,N′‐dihexylterephthalamide (DHT) and N,N′‐dihexylisophthalamide (DHI) as models of the amide functionality. DHT was reacted in an inert argon atmosphere at 350°C in the presence of CuI added in amounts ranging from 0–5% by weight. The rate of disappearance of DHT was enhanced by a factor of three with the addition of 0.5% CuI. Increases to 5 wt % did not change the disappearance kinetics further. Comparison of the behavior of DHT and DHI revealed that changes in rate of disappearance and product yields were dependent on the relative positions of the amide substituents. Reaction of DHI was enhanced more significantly at a given CuI loading. The rate of disappearance of DHI and DHT and the selectivity to N‐hexylbenzamide increased with the addition of water in loadings ranging from 0.148M to 0.193M. The reactivity of DHI was more greatly enhanced at a given water loading. These differences were attributed to electronic effects, as evaluated by differences in atomic partial charges, and physical effects. © 1995 John Wiley & Sons, Inc.
Characterization of vanadium‐based olefin polymerization catalyst precursors by solid‐state 51v‐nmr
Authors: McFaddin Douglas , Reinking Mark 
Published: April 2003

AbstractSeveral VOCL3‐based ethylene polymerization catalyst precursors were prepared on silica and studied by solid‐state 51V‐NMR. The structure of the vanadium species in these samples, as determined by 51V‐NMR, did not have any significant effect on the resultant polyethylene MI or MWD. This result is significant since conventional wisdom says the attachment of the transition metal to the silica plays a key role in polymer properties. VOCl3 reacted with hexamethyldisilazane‐treated silica and with 250°C dried silica results in double attachment of the vanadium to the silica, yet the catalysts which formed had different reactivities and produced polyethylene with different HLMIs. On the other hand, VOCl3 reacted with 600°C dried silica results in single attachment of the vanadium to the silica, yet this catalyst had a similar reactivity and produced polymer properties similar to the doubly attached vanadium on 250°C dried silica. Two theories are offered to explain the lack of correlation between catalyst precursor structure and catalyst performance. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of anionic graft copolymers containing poly(ethylene oxide) grafts
Authors: Dérand Helene , Wesslén Bengt 
Published: April 2003

AbstractAnionic graft copolymers were synthesized through grafting of poly(ethylene glycol) monomethyl ether (MPEG) onto terpolymers containing succicinic anhydride groups. The backbone polymers were prepared through radical terpolymerization of maleic anhydride, styrene, and one of the following monomers: methyl methacrylate, ethylhexyl methacrylate, and diethyl fumarate. MPEG of different molecular weights were grafted onto the backbone through reactions with the cyclic anhydride groups. In this reaction one carboxylic acid group is formed together with each ester bond. The molecular weights of MPEG were found to influence the rate of the grafting reaction and the final degree of conversion. The graft copolymers were characterized by IR, GPC, and 1H‐NMR. Thermal properties were examined by DSC. Graft copolymers containing 50% w/w of MPEG 2000 grafts were found to be almost completely amorphous, presumably because of crosslinking, and hydrogen bonding between carboxylic acid groups in the backbone and the ether oxygens in MPEG grafts. © 1995 John Wiley & Sons, Inc.
Synthesis and photopolymerization of monomers bearing isopropenylphenoxy groups
Authors: Crivello J. V. , Lai Y.‐L. 
Published: April 2003

AbstractThe synthesis of a series of monomers containing isopropenylphenoxy groups was carried out. On irradiation with UV light in the presence of onium salt photoacid generators, these monomers undergo a chain extension reaction consisting of a dimerization followed by a Friedel‐Crafts ring closure which results in the formation of polymers with indane groups in the backbone. Aryl imide‐containing monomers bearing isopropenylphenoxy groups were also shown to undergo facile photoinduced cationic polymerization. The resulting polymers displayed excellent thermal stability. © 1995 John Wiley & Sons, Inc.
Isotactic poly(acrylonitrile) via ultraviolet irradiation of acrylonitrile‐urea canal complex
Authors: Minagawa Masatomo , Nouchi Kentaro , Tozuka Masahiro , Chujo Riichiro , Yoshii Fumio 
Published: April 2003

AbstractIsotactic poly(acrylonitrile) (PAN) has been prepared by means of a conventional ultraviolet (UV) irradiation apparatus without γ‐ray sources; an acrylonitrile‐urea canal complex was directly formed at the surface of the UV (Hg) emission tube at low temperatures (∼ −78°C). When the complex was UV‐irradiated at this temperature, a stereoregular polymer was formed in the canal. The 13C‐NMR analyses indicate that (1) these PAN are rich in isotactic configuration, (2) the extent of the isotactic triad is in the range of 56−71%, and (3) the penultimate unit effect, 4 (mm) (rr)/(mr)2, is linearly correlated with the ultimate unit effect, (mm)/(rr). From the plots of log{4(mm)(rr)/(mr)2} vs log{(mm)/(rr)}, the anomaly in the polymerization of AN is discussed. The molecular characteristics of the UV canal PAN such as molecular weight, etc., were briefly noted. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of glycine copolymers of nylons 6 and 12
Authors: Franco Lourdes , Xenopoulos Alexander , Subirana Juan A. , Puiggali Jordi 
Published: April 2003

AbstractCopolymers of glycine and 6‐aminohexanoic or 12‐aminododecanoic acid within a range of molar compositions from 80/20 to 5/95 were prepared by solution polycondensation of the adequate proportion of the respective pentachlorophenyl ester hydrobromides. Despite their random composition, the copolymers obtained were found to be highly crystalline. Intrinsic viscosities of 2/6 and 2/12 copolyamides were similar and rather low (Mn, ca. 3000‐5000). Thermal post‐polycondensation allowed to increase the molecular weight of 2/12 copolyamides, so that fibers could be prepared. The composition and sequence distributions were evaluated by means of 1H‐ and 13C‐NMR spectroscopies. Copolyamides were also characterized in terms of thermal properties. Melting and glass transition temperatures are reported. Crystallinity was evaluated from heats of fusion. Crystalline structure was examined by infrared spectroscopy and wide‐angle x‐ray diffraction. The presence of structures related to the polyglycine I and to α/γ‐nylons was confirmed depending on the molar composition. Highly oriented fibers with good tensile properties were obtained from the nylon 2/12 (10 : 90) copolymer. © 1995 John Wiley & Sons, Inc.