bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new synthetic route to polycarbonate
Authors: Soga K. , Hosoda S. , Ikeda S. 
Published: April 2003

AbstractA detailed study has been carried out on the new synthetic reaction of poly(p‐xylylene carbonate) from potassium carbonate and p‐xylylene dibromide by using a variety of crown ethers as a catalyst, which was recently found by the present authors. Crown ethers having 18‐member ring showed the best catalytic property of the various crown ethers, and the reaction was conducted in various solvents at 50–160°C by using 18‐crown‐6‐ether. Both the polymer yield and the molecular weight of the polymer increased in proportion to the amount of potassium carbonate, and they increased rapidly and reached constant values with increasing the concentration of 18‐crown‐6‐ether. They also depended significantly upon the reaction temperature as well as the solvent used. A maximum yield with the highest molecular weight was obtained from the reaction at 100–120°C in diglyme solvent. The spectroscopic analysis of the polymer indicated that all the end groups of the resulting polymer had the structure of benzyl bromide. From these results, a plausible mechanism was proposed for the reaction. Similar reactions were also conducted by using several aliphatic dibromides, Br(CH2)xBr, in place of p‐xylylene dibromide. The products were strongly dependent of the value of x: polycarbonate was obtained from dibromides with ≧4, and cyclic carbonates from dibromides with ≦3.
Aqueous polymerization of acrylamide
Authors: Shukla J. S. , Singh Khajan 
Published: April 2003

AbstractThe polymerization of acrylamide (I) initiated by a potassium bromate—thioglycollic acid (TGA) redox pair has been studied in aqueous media at 30°C in a nitrogen atmosphere. The reaction order related to the catalyst concentration (KBrO3) was 0.501, which indicated a bimolecular mechanism for the termination reaction in the range of 1.0−3.0 × 10−3 mole/liter. The polymerization rate varied linearly with monomer (I) concentration over the range of 1.0−5.0 × 10−2 mole/liter. A typical behavior is observed, however, by changing the thioglycollic acid concentration. The initial rate of polymerization (Ri), as well as the maximum conversion, increases by increasing the temperature to 30°C, but the initial rate and the maximum conversion falls as the temperature rises above 30°C. The overall energy of activation is 6.218 kcal in the temperature range of 20–40°C. Water‐miscible organic solvents, namely, CH3OH and C2H5OH, depress the rate of polymerization.
Effect of pressure on free radical copolymerization kinetics. II. Novel methods of measuring monomer reactivity ratios under high‐pressure conditions
Authors: Van Der Meer R. , German A. L. 
Published: April 2003

AbstractTwo new techniques for the determination of monomer reactivity ratios in copolymerization under high‐pressure conditions have been developed, viz., the “sandwich” and the “quenching” method. Both methods are based on repeated quantitative gas chromatographic analysis of the reaction mixture during the low‐pressure stages preceding and succeeding the high‐pressure stage, of which the kinetics is under investigation. Application of the “sandwich” method implies the occurrence of reaction during both low‐pressure stages and consequently the low‐pressure kinetic data are required to obtain the transition points of low to high pressure and vice versa. These points constitute the initial and final conditions of the relevant high‐pressure reaction. On the contrary, in the “quenching” method no reaction occurs during the low‐pressure stages, owing to the lower temperature and the high activation energy of the initiator decomposition. As a consequence, the initial and final conditions of the high‐pressure stage can be determined by a simple averaging procedure. Both methods have been tested for the ethylene—vinyl acetate copolymerization at 62°C and 600 kg/cm2 with tert‐butyl alcohol as solvent, and appear to lead to almost identical monomer reactivity ratios, although the “quenching” method is slightly preferred in case of copolymerization reactions. Both methods are particularly valuable when one of the reactants is gaseous or the reaction produces a gas. Further merits and drawbacks of both methods are discussed.
Pseudoheterogeneous polymerization of methyl methacrylate initiated by sodium bisulfite in presence of glassy powder of PbOSiO2
Authors: Moustafa A. B. , Badran A. S. 
Published: April 2003

AbstractThe aqueous polymerization of methyl methacrylate with sodium bisulfite as initiator was catalyzed by PbOSiO2, PbO (70 mole %)SiO2 (30 mole %) with a particle size < 200 mesh had the highest catalytic effect. The average molecular weight obtained in the presence of amorphous PbOSiO2 glass was higher than that obtained in the presence of crystalline PbO—SiO2 glass powder. In this system mild shaking increased the rate of polymerization. Silicon dioxide catalyzed the rate of polymerization to a higher extent than PbO, which had a slightly higher catalytic effect than lead silicate powder. The average molecular weight formed in the presence of PbO was higher than that formed in the presence of lead silicate, which in turn was higher than that formed in the presence of silicon dioxide. Increasing the initiator concentration decreased the average molecular weight. Mild shaking decreased the average molecular weight obtained when polymerization was carried out in air but increased it in a nitrogen atmosphere. Methanol decreased the conversion percentage of monomer to polymer and the average molecular weight due to its transfer reaction.
Thermal oligomerization of isophthalonitrile catalyzed by o‐carborane
Authors: Klingen T. J. , Johnson B. M. 
Published: April 2003

AbstractThe thermal reaction of equimolar quantities of isophthalonitrile and o‐carborane has been shown to produce an adduct oligomer of isophthalonitrile. The structure was determined to involve condensation of three to five isophthalonitrile molecules to form a triazine‐type system. This type of bonding gave rise to a trimer and pentamer. Further, the reaction was a homogeneous liquid phase reaction in which o‐carborane is involved in a catalytic manner in the oligomerization. The overall reaction has first‐order kinetics with an activation energy of 32.2 kcal/mole.
High‐molecular‐weight hydrolyzed polyacrylamides. I. Characterization. Effect of salts on the conformational properties
Authors: Muller G. , Laine J. P. , Fenyo J. C. 
Published: April 2003

AbstractThe effect of ionization (α) and added salts (NaCl, CaCl2, MgCl2) on the dimensions of commercially available high‐molecular‐weight polyacrylamides (Mw ≃ 4 × 106), hydrolyzed at various extents (0.04 < τ < 0.49) and which have been characterized, was investigated by viscosity and light‐scattering measurements performed at 25°C. The data point with evidence to the strong dependence of the chain dimensions on the charge density (ατ) and the effect of the nature and concentration of added salts. From a practical point of view it is shown that there is no advantage to using too highly hydrolyzed samples (τ > 0.45) in media containing large amounts of salts that lead to precipitation of polymers, especially in the presence of divalent ions.
Peroxide‐initiated crosslinking of maleic anhydride‐modified low‐molecular‐weight polybutadiene. I. Mechanism and kinetics of the reaction
Authors: Gancarz I. , Łaskawski W. 
Published: April 2003

AbstractThe crosslinking mechanism and kinetics of low‐molecular‐weight polybutadiene, its mixtures with maleic anhydride, and the products of its grafting with maleic anhydride and styrene, using dicumyl peroxide (DCP) as an initiator, were studied. It was shown that for all systems crosslinking is a radical polymerization of the double bonds. Modification of polybutadiene changes only the kinetic parameters of the crosslinking reaction and causes mainly a decrease of the termination step velocity. From DSC data the crosslinking reaction order, activation energy, and reaction heats were calculated.
Effect of structure on the thermal stability of polyimides
Authors: Varma I. K. , Goel R. N. , Varma D. S. 
Published: April 2003

AbstractPolyimides with different proportions of m‐phenylene and p‐phenylene (or p,p′‐biphenylene) were prepared by polymerizing different molar ratios of m‐phenylene diamine and p‐phenylene diamine (or p,p′‐diaminobiphenyl) with pyromellitic dianhydride in dimethylformamide at 0°C. Chemical cyclodehydration of polyamic acids resulted in the corresponding polyimides. Polymers were characterized by infrared (IR), viscosity, and density measurements. Viscosity and density of polymers decreased with an increase on m‐phenylene groups in the backbone. The thermal and thermooxidative stabilities were investigated by dynamic thermogravimetry. Stability decreased when m‐phenylene groups were introduced in the backbone.
Chemical modification of polymers. XI. Photoreactive polymers from poly(vinylbenzyl chloride)
Authors: Gibson Harry W. , Bailey F. C. , Chu Joseph Y. C. 
Published: April 2003

AbstractPhotocrosslinking has been observed in a number of polymers derived by chemical modification of poly(vinylbenzyl chloride). Included are polymers bearing pendant benzophenone, stilbazolium, fluorenone, carbazole, and sulfonylazido moieties. The synthesis and properties of these polymers are described.
Functional monomers and polymers. XXXXVII. Complex formation of stereoregular methacryloyl‐type polymers containing nucleic acid bases
Authors: Akashi M. , Okimoto T. , Inaki Y. , Takemoto K. 
Published: April 2003

AbstractThe complex formation between a poly(N‐β‐methacryloyloxyethyl) derivative of adenine with one of thymine or uracil was studied in dimethyl sulfoxide and ethylene glycol mixture by ultraviolet (UV) spectroscopy. For the polymer pairs containing complementary nucleic acid bases both hypochromicity and hyperchromicity were found. Stereoregularity of the polymers, as well as the conditions for measurement of, for example, solvent, temperature, and time, affected the complex formation. Both inter‐ and intramolecular interaction of polymers in solution were discussed in some detail.
Photoinitiated cationic polymerization with triarylsulfonium salts
Authors: Crivello J. V. , Lam J. H. W. 
Published: April 2003

AbstractTriarylsulfonium salts Ar3S+MX with complex metal halide anions such as BF, AsF, PF, and SbF are a new class of highly efficient photoinitiators for cationic polymerization. In this article we describe several synthetic routes to the preparation of these compounds along with their physical and spectroscopic properties. Mechanistic studies have shown that when these compounds are irradiated at wavelengths of 190–365 nm carbon–sulfur bond cleavage occurs to form radical fragments. At the same time the strong Br∅︁nsted acid HMXn, which is the active initiator of cationic polymerization that takes place in subsequent “dark” steps, is also produced. A study of the parameters that affect the photolysis of triarylsulfonium salts is reported with a measurement of the absolute quantum yields. The cationic polymerizations of four typical monomers—styrene oxide, cyclohexene oxide, tetrahydrofuran, and 2‐chloroethyl vinyl ether—with triarylsulfonium salt photoinitiators are described.
Problems associated with the surface characterization of polystyrene latices
Authors: Goodall A. R. , Hearn J. , Wilkinson M. C. 
Published: April 2003

AbstractIt has been shown that polystyrene latices prepared by the surfactant free emulsion polymerization process often contain sufficient residual monomer and possibly low‐molecular‐weight material and reaction by‐products, such as benzaldehyde, which are not efficiently removed by dialysis, to affect their bulk and surface characteristics. These materials have been identified by gel permeation chromatography (GPC) and infrared (IR) spectroscopy studies and their effective removal by steam stripping has been investigated. Steam stripping has proved to be efficient in this process but it led to rapid hydrolysis of the surface sulfate groups and a consequent change in the surface characteristics. The problem of hydrolysis of sulfate groups under various environments has been studied. The problems associated with the identification of weak acid end groups are discussed and several alternative explanations for their occurrence are advanced.
Molecular weight standards from sulfonation of polystyrene
Authors: Brown D. W. , Lowry R. E. 
Published: April 2003

AbstractPolystyrene was sulfonated with sulfur trioxide–triethyl phosphate complexes in dichloroethane, the object being to prepare polystyrene sulfonates substantially free of sulfone links between polymer chains. Variations in the sulfone content with reaction conditions were conveniently followed by exclusion chromatography, the sulfone peak appearing at about twice the molecular weight of the main peak. The desired products were obtained from polystyrenes with molecular weights between 1.1 × 105 and 8.7 × 105 by using (at −20 to +25°C) a 5:1 excess of a 1.5:1 complex, the last at a concentration of 0.5M. Completely soluble polystyrene sulfonate was also obtained from polystyrene of molecular weight 2.05 × 106. Requirements for the successful use of the 1.5:1 complex include careful purification of the dichloroethane and, if 2 g or more polystyrene is to be sulfonated, formation of the complex at −20°C. A method is given for measuring the sulfonating capability of the reagent before adding the polymer.
Effect of interfacial chemical bonding on the strength of adhesion of glass–polybutadiene joints
Authors: Runge M. L. , Dreyfuss P. 
Published: April 2003

AbstractA new example of a positive effect of interfacial chemical bonding on the strength of adhesive bonds is reported. The chemical bond was formed between a p‐bromomethylphenylpolysiloxane‐coated glass slide and a liquid dicarboxy‐terminated polybutadiene that was subsequently bonded to an elastomeric polybutadiene by crosslinking with dicumylperoxide. Peel tests at 180° led to cohesive failure in the elastomer layer for two different proportions of p‐bromomethylphenyl groups on the glass slides, whereas uncoated slides and slides coated with an inert polysiloxane layer, p‐tolyl‐polysiloxane, showed interfacial failure. Further confirmation of interfacial bonding was obtained from SEM studies. When peel tests resulted in cohesive failure, it was found possible to distinguish between different degrees of interfacial by the different times required for failure at the interface on swelling the elastomer layer with pentane.
Heat‐curable polyaromatic keto‐ether‐sulfones. XIV. More polymers with 2,2′‐diphenylethynyl‐4,4′‐diphenyl units and their rearrangement products
Authors: Frentzel Richard L. , Marvel C. S. 
Published: April 2003

AbstractPolymers were prepared from 4,4′‐diphenoxydiphenylsulfone, isophthaloyl dichloride, and bis‐p‐phenoxyphenyl‐4,4′‐(2,2′‐dibromodiphenyl)ketone, 2,2′‐dibromodiphenyl‐4,4′‐dicarbonyl dichloride, or bis‐p‐phenoxyphenyl‐4,4′‐(2,2′‐diphenylethynyldiphenyl)ketone in Friedel‐Crafts type of polymerization. Bromine groups were subsequently replaced with phenylacetylene residues, and the polymers were cured at high temperatures, with the apparent formation of benzanthracene linkages. Cured polymers exhibited higher softening points, decreased solubilities, and, in some instances, higher melting points than their uncured precursors. Significant weight losses occurred during isothermal aging tests.
The charge‐transfer polymerization of nitroethylene in electron‐donating solvents
Authors: Kushibiki Nobuo , Ogasawara Masaaki , Yoshida Hiroshi 
Published: April 2003

AbstractThe anionic polymerization of nitroethylene was studied in N,N‐dimethylformamide (DMF) and in dimethyl sulfoxide (DMSO) at 0–40°C. The polymerization proceeds spontaneously when monomer is mixed with solvent in the absence of light. From the observed results of the rate of polymerization, the molecular weight of polymer, the effects of additives and solvents, the copolymerization with acrylonitrile, and the optical absorption spectra it is concluded that the polymerization is initiated by the nitroethylene radical anion generated by the slow dissociation of the electron donor–acceptor (EDA) complexes between the solvent molecule and the monomer. The activation energy for the rate of polymerization was 50 and 29 kJ/mole in DMF and DMSO, respectively, which seems to be determined primarily by the dissociation of the EDA complexes. The significant features of this polymerization are that the initiation proceeds slowly and there is essentially no termination.
Polyimidines: A new class of polymers. III. A comparison of isomers of polypyromellitimidines
Authors: Cassidy Patrick E. , Lin J‐C. , Fawcett Newton C. 
Published: April 2003

AbstractThe cis (3,3,5,5‐), trans (3,3,7,7‐), oxo, and thio analogs of tetraphenylpyromellitide were polymerized with 1, 6‐hexane diamine, p‐phenylene diamine, and p,p'‐diaminodiphenyl ether under various conditions. A comparison was then made of reactivity of the isomers and of the properties of the polymers. In general the thio monomers were more soluble and reactive than the oxo. They also gave more thermally stable polymers. The cis isomers of the monomers were more soluble than the trans, but the trans were more reactive. The least stable of the 12 polymers prepared was that from the cis–oxo monomer and 1,6‐hexane diamine. It gave a 10% weight loss at 300°C in air and 340°C in nitrogen by TGA. The most stable polymer was from the reaction of the cis–thio pyromellitide with p,p'‐diaminodiphenyl ether, which showed 10% weight losses by TGA at 560 and 650°C in air and nitrogen, respectively. The polymers were stable in hot dilute hydrochloric acid and sodium hydroxide. They were all soluble in chloroform, dimethylformamide, and sulfuric acid. Polymers that contained sulfur were also soluble in carbon tetrachloride, benzene, xylene, and toluene. Brittle films could be cast from solution or melt‐pressed.
Electroinitiated polymerization of arylvinyl monomers
Authors: Smith J. D. B. , Phillips D. Colin , Davies D. H. 
Published: April 2003

AbstractThe electroinitiated polymerizations of styrene, 2‐vinylnaphthalene, and 9‐vinylanthracene were compared in sulfolane and acetone solvents in the presence of ZnCl2. The relative orders of polymerization rates and polymerization efficiencies, in both solvents, were 9‐vinylanthracene > 2‐vinylnaphthalene > styrene, with faster rates and higher efficiencies occurring in sulfolane. Data obtained from viscosity and gel permeation chromatography (GPC) studies indicate that the molecular weights of the polymers produced in these systems are extremely low, <5000. Chemical composition and infrared (IR) spectral data suggest that abnormal transfer reactions (possibly from solvent) may be occurring in the electroinitiated 9‐vinylanthracene polymerizations. The polymerization mechanism appears to be cationic in these monomer–solvent systems with ZnCl2.
Monomer‐isomerization polymerization. XVIII. Monomer‐isomerization copolymerizations of 4‐phenyl‐2‐butene with 4‐methyl‐2‐pentene and 3‐heptene with Ziegler‐Natta catalyst
Authors: Endo Kiyoshi , Otsu Takayuki 
Published: April 2003

Abstract4‐Phenyl‐2‐butene (4Ph2B) undergoes monomer‐isomerization copolymerization with 4‐methyl‐2‐pentene (4M2P) and 2‐and 3‐heptene (2H and 3H) with TiCl3–(C2H5)3Al catalyst at 80°C to produce copolymer consisting exclusively of 1‐olefin units. For comparison the copolymerization of 4‐phenyl‐1‐butene (4Ph1B) with 4‐methyl‐1‐pentene (4M1P) and 1‐heptene (1H) was carried out under similar conditions. The composition of the copolymers obtained from these copolymerizations was determined from the ratios of optical densities D1380 and D1600 of infrared (IR) spectra of their thin films. The apparent monomer reactivity ratios for the monomer‐isomerization copolymerization of 4Ph2B with 4M2P, 2H, and 3H in which the concentration of olefin monomer in the feed was used as internal olefin and those for the copolymerization of 4Ph1B with 4M1P and 1H were determined as follows: 4Ph2B(M1)‐4M2P(M2); r1 = 0.90, r2 = 0.20, 4Ph1B(M1)‐4M1P (M2); r1 = 0.40, r2 = 0.70, 4Ph2B(M1)‐2H(M2); r1, = 0.45, r2 = 1.85, 4Ph2B(M1)‐3H(M2); r1 = 0.50, r2 = 1.20, 4Ph1B(M1)‐1H(M2); r1 = 0.55, r2 = 0.75. The difference in monomer reactivity ratios seemed to originate from the rate of isomerization from 2‐ or 3‐olefins to 1‐oletins in these monomer‐isomerization copolymerizations.
Thermal oxidative degradation of isotactic polypropylene catalyzed by copper and copper oxide interfaces
Authors: Jellinek H. H. G. , Kachi H. , Czanderna A. , Miller A. C. 
Published: April 2003

AbstractThe oxidative degradation of isotactic polypropylene films coated on well‐defined Cu(Cu2O), CuO0.67, and CuO films in a temperature range of 90–120°C in a quartz‐spoon‐gauge‐reaction vessel was studied. This catalytic reaction has been compared with the oxidation of polypropylene without copper or oxide films. The reaction vessel contained, if needed, P2O5 and/or KOH as “getters” for H2O and CO2, these substances could be menitored continuously. Cu(Cu2O) films were transformed during oxidation of the polymer to yellow CuO0.67 below 100°C and above this temperature to black CuO in the presence of H2O and CO2, whereas in the absence of these compounds CuO was formed below 100°C and CuO0.67 at 120°C. Characteristic autoxidation curves obtained in the absence of H2O and CO2 showed induction periods that were shorter for copper oxide‐polymer interfaces than for glass‐polymer interfaces (i.e., for uncatalyzed oxidation). Abnormalities were observed for Cu(Cu2O)‐polymer interfaces because of further oxidation of Cu during the reaction. The rates of oxygen consumption were faster for CuO0.67‐polymer and CuO‐polymer than for the uncatalyzed reaction; the catalytic action of CuO0.67 was somewhat larger than that of CuO. The important observation was made that the mechanism of oxidation is not the same in the absence and presence of reaction products; that is, H2O and CO2. This was confirmed by ion beam scattering experiments, which also revealed that an oxidation‐reduction process takes place at Cu and their oxide interfaces. A mechanism for the catalytic oxidation process, based on the ease by which copper ions are released from the metal oxides at the interface, was formulated. These ions diffuse subsequently as actions of carboxylate anions into the bulk of the polymer. Arrhenius equations of oxygen consumption are given for all cases; the energy of activation calculated for the initiation of the uncatalyzed oxidation agrees with its literature value. The energy of activation for the initiation of the catalyzed reaction was a few kilocalories lower than that for the uncatalyzed reaction. Catalytic action is mainly operative for the initiation reaction at the interface and for the decomposition of hydroperoxides by copper ions. Preventing the delivery of copper ions to the polymer would be the most efficient way of inhibiting the catalysis.
Dual role of a hydroxyphenylbenzotriazole UV absorber in the photooxidation of wool
Authors: Leaver I. H. , Waters P. J. , Evans N. A. 
Published: April 2003

AbstractThe protective effect of the UV absorber, sodium 2‐(2′‐hydroxy‐5′‐methylphenyl)benzotriazole sulfonate, on the light stability of wool has been examined. The degree of protection, as measured by the reduction in the rate of photoyellowing of the fiber, is highly dependent on both the spectral composition of the light source and the pH at which the absorber is applied to the fiber. This is due mainly to traces of the deprotonated, phosphorescent form of the absorber which can sensitize the photooxidation of wool in visible light, hence counteracting the photostabilizing influence of the UV absorber.