bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aromatic polyamides. III. Copoly(4,4′‐oxanilideterephthalamide—4,4′‐phenyleneterephthalamide): Synthesis, wet‐spinning, fiber thermal characterization, and stability in sulfuric acid
Authors: Silver Frank M. , Dobinson Frank , Ridgway James S. 
Published: April 2003

AbstractCopoly(4,4′‐oxanilideterephthalamide—4,4′‐phenyleneterephthalamide) (A‐202/PPD) was synthesized by reaction of 4,4′‐diaminooxanilide, p‐phenylenediamine, and terephthaloyl chloride in organic solvents. Copolymer inherent viscosities in H2SO4 as high as 10.3 were obtained. Isotropic copolymer solutions (4%—5% concentration) of A‐202/40%–80% PPD were spun to fibers with tenacity/elongation/modulus at 1% extension in the 13–14 gpd/1.5%–2%/700–1000 gpd range. Oxamide and amide stabilities in 98–100% H2SO4 and 20% oleum were compared. Poly(4,4′‐oxanilideterephthalamide) (A‐202), A‐202/PPD copolymers, and poly(4,4′‐phenyleneterephthalamide) (PPT) were unstable in 20% oleum, but all proved relatively stable in 100% H2SO4. However, the oxamide linkage proved less stable than the amide linkage in 98% H2SO4. A‐202 and A‐202/PPD copolymers formed stable anisotropic spinning solutions in 1% oleum at 10–20% concentrations. Dynamic mechanical analyses (Vibron) showed no glass transition temperature (Tg) below 200°C. Dilatometric measurement of A‐202/50% PPD revealed a Tg at 257°C. Differential thermal analyses of A‐202/40–80% PPD exhibited endotherms at 470–480°C. Thermogravimetric analyses showed no significant weight loss below 400°C.
Polymerization of isoprene initiated by the reaction products of η3‐allyl complexes of transition metals and titanium chlorides
Authors: Vasiliev V. A. , Sokoryanskaya T. I. , Kormer V. A. 
Published: April 2003

AbstractThe main path of the interaction of chromium and nickel η3‐allyl complexes and titanium tetrachloride is the transfer of allyl ligands to titanium with the concomitant reduction of TiCl4 to η‐TiCl3 and the formation of the products initiating isoprene polymerization. The stereospecific effect of the system is because of the formation of bimetallic complexes with bridged metal—carbon bonds which are the most probable centers of stereospecific cis‐1,4‐polyisoprene chain propagation.
Thermal degradation of mixtures of poly(methyl methacrylate) and silver acetate
Authors: Jamieson A. , McNeill I. C. 
Published: April 2003

AbstractThe degradation behavior of silver acetate—PMMA blends at salt/polymer ratios of 1:1, 1:5, and 1:10 has been studied by using thermal volatilization analysis (TVA) as the principal technique. Degradation of the salt has also been examined; it gives a variety of products best explained by a series of reactions resulting from an initial cleavage of CH3COO. radicals and silver atoms. Silver acetate, when present with PMMA during degradation, results in a severe destabilization of the polymer, which breaks down to monomer at a high rate at temperatures as low as 200°C. This effect is explained by diffusion of radicals from silver acetate decomposition into the polymer phase, in which they initiate chain scission and depolymerization.
Redetermination of the crystal structure of calcium acrylate dihydrate at 183 K
Authors: Page Yvon Le , Fortier Suzanne , Donnay Gabrielle 
Published: April 2003

AbstractThe crystal structure of (CH2CHCO2)2Ca.2H2O is different from that reported in the literature. Single‐crystal intensities were collected at 183 ± 5 K and the structure was refined with 564 trustworthy reflections to a residual of 6.6% in space group P21/a. Cell dimensions are a = 14.11(2), b = 6.63(1), c = 11.76(2)Å, and β = 118.4(1)°, Z = 4. The structure consists of dimolecular layers 10 Å thick, parallel to (001) and joined by van der Waals attractions. Each layer contains two sheets of acrylate groups on its outside borders that point toward a central sheet of eight‐coordinated calcium ions and hydrogen‐bonded water molecules. One of the two symmetry‐independent acrylate groups is planar; the other deviates significantly from planarity. Calcium ions surround the nonplanar molecule in a lopsided fashion.
Low‐molecular‐weight polybenzimidazoles from aromatic dinitriles and aromatic diamines
Authors: Brand Richard A. , Bruma Maria , Kellman Raymond , Marvel C. S. 
Published: April 2003

AbstractThree oligomeric benzimidazoles have been prepared by the oxidative cyclization of the corresponding polyamidines. These materials are high melting and are soluble in solvents like dimethylformamide. They exhibit inherent viscosities of 0.20–0.25 in DMF at 0.5g/100 ml. Several model compounds have also been prepared to show the feasibility and scope of the oxidative cyclization reaction.
Sorption of ethanesulfonic acid by nylon‐6 containing various numbers of end groups
Authors: Obara T. , Iijima T. , Komiyama J. , Ikeda S. , Ishikawa H. , Nakagawa T. 
Published: April 2003

AbstractFrom the analysis of the permeation of 35S labeled ethanesulfonic acid, through nylon‐6 films sorption isotherms were obtained. The films are characterized by their largely different content of carboxyl and amino end groups. It was found that the shape of the isotherm depends on the molar ratio of the two end groups: an S‐shape curve for the film containing the carboxyl end group larger than the amino end group and a Langmuir‐type curve for the film containing comparable numbers of end groups. These results were explained by the McGregor‐Harris theory in which the acid dissociation constants of the two end groups in nylon were estimated experimentally.
Interaction between dyes and polyelectrolytes. X. Excitation energy transfer in cationic dye–polyanion system
Authors: Shirai Masamitsu , Nagatsuka Tatsuki , Tanaka Makoto 
Published: April 2003

AbstractThe quantum yield for the trypaflavine‐photosensitized oxidation of 1‐(methylthio)ethyl‐3‐carbamoylpyridinium chloride to 1‐(methylsulfinyl)ethyl‐3‐carbamoylpyridinium chloride increased with increase in the concentration of methylene blue added. It was inferred that the increase in the quantum yield is due to the excitation energy transfer from trypaflavine to methylene blue. The efficiency of excitation energy transfer was enhanced on addition of potassium poly(vinyl sulfate) and was dependent on the polyanion/dye ratio. The efficiency of excitation energy transfer at the most appropriate polyanion/dye ratio was about 5 times as high than that in the absence of polyanion. The binding of dye to potassium poly(vinyl sulfate) was investigated spectrophotometrically. Correlation with the dye binding to potassium poly(vinyl sulfate) and the efficiency of excitation energy transfer between dyes was discussed.
Dye‐sensitized photoinitiated cationic polymerization
Authors: Crivello J. V. , Lam J. H. W. 
Published: April 2003

AbstractSeveral dyes have been discovered which sensitize the photolysis of diaryliodonium salts at visible wavelengths. By using the combination of a dye and a diaryliodonium salt, visible light can be used to photoinitiate cationic polymerization. In this article, the dye‐sensitized photopolymerizations of cyclohexene oxide, epichlorohydrin, and 2‐chloroethyl vinyl ether are described.
Reactivity of cobaloxime bound to polystyrene chain by carbon–cobalt σ bond
Authors: Nishikawa Hiroshi , Terada Ei‐Ichi , Tsuchida Eishun , Kurimura Yoshimi 
Published: April 2003

AbstractThe (alkyl)‐bis(dimethylglyoximato)pyridinecobalt attached to polychloromethylstyrene by a cobalt–carbon bond was prepared by the reaction of Co(II)(DH)2Py with polychloromethylstyrene in benzene. The fraction of p‐vinylbenzyl·Co(DH)2Py introduced to the polymer was 8.1 and 2.1 mole %. The photodecomposition of the polymer‐bonded cobaloxime was investigated by following the change of the visible spectrum. The rate constant kdec of the polymer‐bonded cobaloxime was 1.1 × 10−2 sec−1 in benzene; it is one‐fourth of that of its monomeric analog, benzyl·Co(DH)2Py. The kdec values of the cobaloximes were also measured in benzene–dimethyl sulfoxide mixed solvents, and the polymer effects were discussed. The dependence of the photodecomposition on energy of the irradiation light was investigated, and it was found that the absorption band near 470 nm is important for the photodecomposition of the cobalt–carbon bond. Spectroscopic measurements of the ligand exchange reaction of polymer‐bonded cobaloxime with pyridine in dimethyl sulfoxide gave a larger equilibrium constant (1.2 × 104 liter/mole) than that of benzyl·Co(DH)2Py (9.4 × 102 liter/mole). The kinetic data of the ligand exchange reaction indicated that the larger equilibrium constant for the polymeric system is due to the smaller rate constant of the reverse reaction. The thermodynamic parameters were also obtained.
Unequivocal synthesis of bis(2‐cyanoacrylate) monomers. I. Via anthracene adducts
Authors: Buck Carl J. 
Published: April 2003

AbstractAn unequivocal and general synthesis of bis(2‐cyanoacrylate) monomers from Diels‐Alder adducts of the alkyl 2‐cyanoacrylates has been developed. Saponification of the anthracene adduct of either isobutyl or ethyl 2‐cyanoacrylate to the anthracene/2‐cyanoacrylic acid adduct, conversion of the latter to the alkali salt or acid chloride derivatives, followed by respective esterification reactions with an organic dihalide or glycol gave the bis‐anthracene adduct precursors to the bis(2‐cyanoacrylate) monomers. Heating the bis‐adducts with excess maleic anhydride in refluxing xylene effected retrograde diene scission to the bis(2‐cyanoacrylate) monomers in up to 80% overall yields. Comonomer blends of the difunctional bis(2‐cyanoacrylates) with the alkyl 2‐cyanoacrylates gave crosslinked polymeric adhesive compositions exhibiting higher bond strengths under both dry and wet conditions than the noncrosslinked cyanoacrylate adhesives. Potential applications of interest are as pit and fissure sealants in dentistry and for the direct bonding of orthodontic attachments.
Preparation and degradation of head‐to‐head PVC
Authors: Crawley S. , McNeill I. C. 
Published: April 2003

AbstractThe course of the chlorination reaction of cis‐1,4‐polybutadiene is dependent on the choice of solvent. When methylene chloride is used, a pure addition reaction of chlorine leads to a polymer with the structure of head‐to‐head, tail‐to‐tail PVC. The thermal stability of the head‐to‐head PVC polymer has been studied by thermal volatilization analysis, thermogravimetry, and evolved gas analysis for hydrogen chloride, and the changes in the ultraviolet (UV) spectrum of the polymer during degradation have been investigated. The head‐to‐head polymer has a lower threshold temperature of degradation than normal PVC, but reaches its maximum rate of degradation at a higher temperature for powder samples of the polymer under programmed heating conditions. Blends of head‐to‐head PVC with poly(methyl methacrylate) have also been degraded, and the presence of the head‐to‐head polymers, like that of normal PVC, results in depolymerization of the PMMA as soon as the dehydrochlorination reaction commences. The mechanism of degradation of head‐to‐head PVC is discussed.
Viscoelasticity of rubber‐resin mixtures
Authors: Aubrey D. W. , Sherriff M. 
Published: April 2003

AbstractThe dynamic viscoelastic response of blends in various proportions of natural rubber with each of two tackifier resins, a poly(β‐pinene) and a pentaerythritol ester of hydrogenated rosin, has been investigated. Results are presented in the form of master curves of the modulus G′r and the viscosity η′r against frequency. The two resins show remarkably similar behavior in modifying the viscoelastic behavior of the rubber; the most obvious effects of increasing resin concentration are (a) a displacement of the transition zone toward lower frequencies, (b) a reduction in width and eventual elimination of the “rubbery plateau,” and (c) a displacement of the terminal zone in the direction of higher frequencies. The effect (a) is interpreted in molecular terms as a restriction of segmental motion and may be quantitatively evaluated in terms of reduced fractional free volume and increased monomeric friction coefficient. Effects (b) and (c) are explicable in terms of reduced average molecular weight, with consequent reduction in entanglement coupling and resistance to viscous flow. Quantitative analysis of the results, using relaxation time spectra, lends support to the iso‐free‐volume theory of the glassy state and shows a correlation between fractional free volume and monomeric friction coefficient.
Radiation‐induced polymerization of glass‐forming systems. VII. Polymerization in supercooled state under high pressure
Authors: Kaetsu Isao , Yoshii Fumio , Watanabe Yuhei 
Published: April 2003

AbstractRadiation‐induced polymerization of glass‐forming monomers such as 2‐hydroxyethyl methacrylate and glycidyl methacrylate under high pressure was studied. The glass transition temperature of these monomers was heightened by increased pressure. The temperature dependence of polymerizability showed a characteristic relation; similar to those in supercooled‐phase polymerization under normal pressure, that had a maximum at Tv which shifted to higher levels of temperature as well as to Tg under high pressure. Polymerizability in the supercooled state also increased under increased pressure.
CIDNP studies of macromolecular systems. I. Photolysis of poly(methyl isopropenyl ketone) and its model compounds in solution
Authors: Bargon Joachim 
Published: April 2003

AbstractThe photoreactions of poly(methyl isopropenyl ketone) (PMIK) and two low‐molecular‐weight model compounds have been investigated in solution with proton NMR spectroscopy. Chemically induced dynamic nuclear polarization (CIDNP) has been observed in all three systems, but the CIDNP intensities have been found to depend on the chain lengths of the reaction products: long‐chain products fail to show CIDNP at room temperature, whereas simultaneously formed small fragments exhibit nuclear spin polarization. The CIDNP originates from the Norrish type I decomposition of the ketones, which for the polymer occurs from the triplet state in all solvents. In the model compounds this cleavage can occur from the triplet or singlet state. The main photoreaction of PMIK, namely, scission of the polymer backbone, does not give rise to CIDNP. The failure of long‐chain products to display CIDNP is attributed in part to a relaxation phenomenon: the short nuclear spin relaxation times of the long‐chain product molecules destroy the CIDNP before it can be detected. In high‐temperature studies above 150°C, however, in which the relaxation times are longer, CIDNP has been detected in long‐chain molecules as well.
Modification of cellulose phosphonate with N,N‐dimethylacrylamide and 4‐vinylpyridine, and flame‐retardant properties of the products
Authors: Inagaki Norihiro , Katsuura Kakuji 
Published: April 2003

AbstractCellulose phosphonate was added to N,N‐dimethylacrylamide (A) and 4‐vinylpyridine (B) in the presence of sodium ethoxide to yield cellulose 2‐(N,N‐dimethyl)carbamoylethylphosphonate and cellulose 2‐pyridinylethylphosphonate, respectively. The extent of the addition was 50% for (A) and 10% for (B), based on P—H bonds in cellulose phosphonate. The modification of cellulose with (A) resulted in an increase in the threshold temperature for weight loss, a decrease in the amount of residual products, and retardation of deammoniation of ammonium salts of the products. Modification of (B) resulted in a lower threshold temperature and amount of residue and an acceleration of the oxidation of cellulose chains. Cellulose phosphonate fabrics modified with (A) had powerful flame‐retardant properties. It was deduced that the combination of phosphoryl and amide groups was an effectual flame retardant.
Synthesis of polyenamines by vinylogous nucleophilic substitution polymerization of 1,6‐diethoxy‐1,5‐hexadiene‐3,4‐dione with diamines
Authors: Ueda Mitsuru , Otaira Kouetsu , Imai Yoshio 
Published: April 2003

AbstractNovel polyenamines with inherent viscosities in the 0.2–1.1 range were synthesized by the vinylogous, nucleophilic substitution polymerization of 1,6‐diethoxy‐1,5‐hexadiene‐3,4‐dione with aromatic and aliphatic diamines in polar aprotic solvents at room temperature. The most effective polymerization medium was hexamethylphosphoramide for preparing high‐molecular‐weight polymers from aromatic diamines. The dilute solutions showed a marked decrease in viscosity with time. The aromatic polyenamines began to lose weight around 200°C under thermogravimetric analysis in air and nitrogen.
Synthesis of novel fluorocarbon ether bibenzoxazole polymers
Authors: Evers Robert C. 
Published: April 2003

AbstractNovel fluorocarbon bis(o‐aminophenol) monomers were synthesized by a multistep route from 1,3‐diiodohexafluoropropane and 1,8‐diiodohexadecafluorooctane. The acetic acid‐promoted polycondensation of these monomers with fluorocarbon ether‐diimidate esters led to linear, soluble fluorocarbon ether‐bibenzoxazole polymers with inherent viscosities in the range of 0.10–0.94 dl/g−1. Polymer structures were verified by elemental and infrared (IR) spectral analysis. Many of the polymers exhibited considerable crystallinity in which the crystalline melt temperatures ranged from 53 to 187°C, as determined by differential scanning calorimetry. Some polymers, however, were isolated as completely amorphous, rubbery gums that exhibited glass transition temperatures as low as −31°C. Good thermooxidative stabilities were exhibited with onset of weight loss of the polymers during thermogravimetric analysis in an air atmosphere occurring in the 375–450°C range.
Diol sequencing in copolyesters
Authors: Mackey John H. , Pattison V. A. , Pawlak J. A. 
Published: April 2003

AbstractHomogeneous condensation of a symmetrical diacyl monomer T with two symmetrical diols D1 and D2 has been studied under low‐temperature, nonequilibrium conditions, using the diol sequence in the product as a probe. For terephthalate copolyesters of diols such as bisphenol A and neopentyl glycol the alternation frequency f12 has been related to the rate parameters by measurement [using nuclear magnetic resonance (NMR) and other methods] and calculation.It is usually assumed that all functionalities attached to the same residue have the same reactivity, that is, that all steps of type

have the same specific rate; this assumption leads to a random, high‐molecular‐weight copolyester. If the diacyl species shows a large penultimate group effect, as in phosgene, chloroformate [see M. Matzner et al., Chem. Rev., 64, 645 (1964)], and phthalates, this assumption must be discarded.After simplification the alternation can be calculated exactly in terms of two parameters: r, the relative reactivity of the diacyl functionalities, and δ, the relative reactivity of the two diols. A nonrandom copolyester results only when neither r nor δ is unity. The maximum nonrandomness (for fixed r) occurs when δ → ∞ (sequential reaction).
Emulsifier‐free emulsion polymerization of tetrafluoroethylene by radiation. I. Effects of reaction conditions on the polymerization rate and polymer molecular weight
Authors: Suwa Takeshi , Watanabe Terutaka , Okamoto Jiro , Machi Sueo 
Published: April 2003

AbstractThe radiation‐induced emulsifier‐free emulsion polymerization of tetrafluoroethylene was carried out at an initial pressure of 2–25 kg/cm2, temperature of 30–110°C, and under a dose rate of 0.57 × 104−3.0 × 104 rad/hr. The rate of polymerization was shown to be proportional to 1.0 and 1.3 powers of the dose rate and initial pressure, respectively, and is maximal at about 70°C. The molecular weight of polytetrafluoroethylene (PTFE) lies in the range of 105−106, increases with reaction time in the early stage of polymerization, and is maximal at 70°C but is almost independent of the dose rate. An interesting discovery is that PTFE, a hydrophobic polymer, forms as a stable latex in the absence of emulsifier. When PTFE latex coagulates during polymerization under certain conditions, the polymerization rate decreases, probably because polymerization proceeds mainly on the polymer particle surface. The observed rate acceleration and successive increase in polymer molecular weight may be due to slow termination of propagating radicals in the rigid PTFE particles.
Photolytic behavior of truxillic and truxinic polyamides
Authors: Caccamese S. , Maravigna P. , Montaudo G. , Recca A. , Scamporrino E. 
Published: April 2003

AbstractThe effect of strong acids on the photolysis of stereoisomeric polyamides containing photoreactive cyclobutane units was studied, and a drastic increase in the photolytic rates was observed. Protonation of amide groups can explain the mechanism of this catalytic effect, being the photolytic rates affected not only by the steric congestion around the cyclobutane ring but also by the basicity of the amide group as a function of the substituent. Molecular weight decrease of the irradiated polymers was monitored by viscosity measurements, and it was found sensibly affected by the presence of small amounts of strong acids.
Diad, triad, and pentad sequence‐distribution analysis of acrylonitrile–vinylidene chloride model copolymers by 13C‐NMR
Authors: Bailey D. B. , Henrichs P. M. 
Published: April 2003

AbstractThe DMSO solution copolymerization of acrylonitrile and vinylidene chloride can be adequately described by the terminal‐unit copolymerization model. The sequence distribution measured by 13C‐NMR is in excellent agreement with the theoretically calculated diad, triad, and pentad distributions. The variation of glass transition temperatures with copolymer composition is explained by sequence distribution.
Storage stability of reactive phenolic dispersions
Authors: Leung M. S. , Wu Y. T. , Jones T. R. , Ancker F. H. , Covitz F. H. 
Published: April 2003

AbstractStorage stability of an aqueous phenolic dispersion resin has been studied by accelerated methods with chemical kinetics and centrifugation. The activation energy of the resin advancement reaction was 25.6 kcal/g mole. Results indicate that the chemical and physical properties of the dispersion resin do not change significantly in a storage period of 4.5 months under normal conditions (25°C). Under refrigeration (4°C) the product is stable indefinitely for all practical purposes.