bluuebunny/crossref_metadata_2025_split huggingface dataset:
Telomerization by free‐radical mercaptan chain transfer. IV. Effects of structure, solvent and initiator variation on the stereochemistry of acrylate ester–mercaptan telomers
Authors: Scott George P. , Elghoul Abdelaziz M. R. 
Published: April 2003

AbstractChain‐transfer constants for radicals one to five units in length were determined for the methyl acrylate–isopropanethiol system. Effects of varying ester alkyl group, mercaptan solvent and initiator on three‐unit diastereomer ratio were also investigated. It was found that the proportion of syndiotactic isomer increased as the size of either the ester alkyl group or the mercaptan increased, the latter result being equivalent to a penultimate effect. Polar solvents, on the other hand, favored the formation of the isotactic form. This effect was observed in the free‐radical telomerization and to an even greater degree in the base‐initiated anionic telomerization. Possible reasons for solvent effects are discussed.
Cyclocopolymerization of p‐chlorostyrene with 4‐vinylcyclohexene
Authors: Kawai Wasaburo , Katsuta Shigeru 
Published: April 2003

Abstract4‐Vinylcyclohexene was polymerized by triethyl‐aluminum–titanium tetrachloride catalyst (mole ratio 5.4:1). Copolymerization of 4‐vinylcyclohexene with p‐chlorostyrene by the same catalyst was also carried out. For these polymerization results, the Roovers‐Smets equation was applied and the reactivity ratio parameters, Kc, Kc′, r2 and r3 were determined as follows: Kc = Kc/k11 = 9.1; Kc′ = kc/k12 ∼ ∞; r2 = k22/k21 = 1.45; r3 = k31/k32 ∼ 0, where subscripts 1, 2 and 3 indicate 4‐vinylcyclohexene, p‐chlorostyrene, and cyclized polymer anion, respectively.
Radiation‐induced copolymerization of tetrafluoroethylene and 3,3,4,4,5,5,5‐heptafluoropentene‐1 under pressure
Authors: Brown Daniel W. , Lowry Robert E. , Wall Leo A. 
Published: April 2003

AbstractAn investigation was made of the γ‐ray‐induced copolymerization of tetrafluoroethylene and 3,3,4,4,5,5,5‐heptafluoropentene‐1. At 22°C at 5000 and 10 000 atm the polymerization rate changes little between 0 and 75 mole‐% tetrafluoroethylene. Above 90 mole‐% the rate increases greatly. Molecular weights vary with composition in a fashion similar to the variation of the rates. Crystallization occurs in the bulk pentene at 13 500 atm at 24°C. The polymerization rate is very low in the solid state. Under some conditions polymerization continues long after irradiation is ended. Both reactivity ratios favor the pentene. Several copolymer properties were studied. The polymers are amorphous and soluble in perfluoro ethers, perfluoro alkanes, and perfluoroaromatics if they contain less than 80% tetrafluoroethylene. The glass temperatures of the amorphous polymers decrease and the thermal and radiation stability increases as the tetrafluoroethylene content increases.
Polymerization studies on allylic compounds. IV. Methallylic compounds
Authors: Harville R. L. , Reed Samuel F. 
Published: April 2003

AbstractThe free‐radical polymerization of a series of 2‐methyl‐3‐substituted propenes was investigated. These compounds were found to homopolymerize with difficulty to give low molecular weight polymers. Their effect upon the polymerization of methyl methacrylate and styrene was investigated by rate and viscosity measurements. Copolymerizations occurred with a retarding action attributed to pronounced chain transfer reactions.
Alkyl chain branching in ethylene–vinyl acetate copolymer
Authors: Saito Mitsutaka , Tada Hideo , Kosaka Yujiro 
Published: April 2003

AbstractEthylene–vinyl acetate copolymers contain two kinds of side chains: acetoxy branches originating from incorporated vinyl acetate and alkyl branches. The alkyl branching was determined by infrared analysis after converting the ethylene–vinyl acetate copolymer to a hydrocarbon polymer by three steps: hydrolysis, iodation with hydriodic acid containing red phosphorus, and reductive hydrogenation with lithium aluminum hydride. It was found that physical properties such as stiffness were dependent both on the degree of alkyl chain branching and on vinyl acetate content.
Polymerization of acrylamide initiated with pinacol–ceric ion redox system
Authors: Narita Hiroshi , Okimoto Tomoyuki , Machida Seishi 
Published: April 2003

AbstractPolymerization of acrylamide initiated with a pinacol–ceric ion redox system was investigated. The polymer obtained was found to contain one cerium atom in a polymer molecule. It was considered that the cerium atom was introduced into the polymer molecule by the termination reaction as there is no cerium atom in the initiating radical in the present system. A similar termination reaction was attained by ferric ion but not by cerous ion. The metal ion was considered to terminate the polymerization to form a stable polymer. Some considerations on the structure of the reaction product relating to the polymerization mechanism were discussed.
Stereospecific polymerization of isobutyl vinyl ether by AlR3–VCln catalysts. I. Influence of preparative conditions of the catalysts
Authors: Joh Yasushi , Yuki Heimei , Murahashi Shunsuke 
Published: April 2003

AbstractThe polymerization of isobutyl vinyl ether by the VCln–AIR3 system was carefully studied. The vanadium components were prepared by the reaction between VCl4 and AlEt3 or n‐BuLi as a reducing agent. VCl3·LiCl and VCl2·2LiCl are the effective catalysts for the stereospecific polymerization of isobutyl vinyl ether. When VCl3·LiCl is combined with AlR3, a new catalytic system is formed. The effect of the preparative conditions of the various vanadium component in the AlR3–VCln system shows that the effective vanadium component is trivalent. In the polymerization by VCl3·LiCl–Al (i‐Bu)3 system, a change of the polymerization mechanism may occur at Al(i‐Bu)3/VCl3·LiCl ratio at around 5. When the ratio is lower than 5, a cationic polymerization by VCl3·LiCl takes place predominantly, while at ratios higher than 5, it is suggested that the polymerization proceeds by means of a VCl3·LiClA–Al(i‐Bu)3 complex by a coordinated anionic mechanism. The polymers obtained by these catalysts are highly crystalline. Styrene was also polymerized by using the same catalysts. VCl3·LiCl and VCl3·LiCl–THF complex yielded amorphous polymer by cationic polymerization. When VCl3·LiCl was combined with 6 mole‐eq of Al(i‐Bu)3, the resulting polystyrene was highly crystalline and had an isotactic structure, while the VCl2·2LiCl–Al(i‐Bu)3 (1:6) system yielded traces of polymer of extremely low stereoregularity. The results indicate that the effective vanadium component at Al/V ≧ 6 is trivalent and that the mechanism is a coordinated anionic one.
Salt‐catalyzed reaction between styrene oxide and silk fibroin
Authors: Shiozaki Hideki , Tanaka Yoshio 
Published: April 2003

AbstractThe addition reaction of styrene oxide (StO) with silk fibroin was studied in the presence of various salts in different solvents at 45–75°C. Some water was required to make StO react with silk padded with various salt solutions. The reaction rate increased with the salt concentration and reached a maximum value at a certain concentration of the salt. Padding with solutions of thiosulfate, cyanide, thiocyanate, bicarbonate, or carbonate resulted in high add‐ons (to 65 mole/105 g) and low solubilities in HCl and NaOH aqueous solutions. The weight gains increased with the epoxide concentration and reached a constant value at a certain concentration of StO solution in ethanol, while they decreased slightly with epoxide concentration over 10% of StO solution in n‐hexane. Histidine, lysine, arginine, tyrosine, and aspartic and glutamic acids were found to react. The reaction rate decreased with increasing solubility parameter of the solvent used, reached a minimum value about at 10 or at the solubility parameter of the epoxide, and then increased with the parameter. The StO–silk reaction may depend on the distribution of StO between aqueous salt and an organic solvent phases, and on the swelling of silk fiber in different aqueous salt solutions or in various organic solvents. The mechanism for this epoxide‐silk reaction and the reactivity difference between StO and phenyl glycidyl ether toward silk fibroin are discussed in the light of the observed phenomena.
Isocyanate–catalyst and hydroxyl–catalyst complex formation
Authors: Reegen S. L. , Frisch K. C. 
Published: April 2003

AbstractAs part of an investigation for evidence of isocyanate–catalyst and alcohol–catalyst complex formations, determinations of molecular weights were made by means of the freezing point depression of benzene solutions. Mixtures of 1‐methoxy‐2‐propanol and dibutyltin dilaurate and mixtures of 1‐methoxy‐2‐propanol and triethylamine both gave strong evidence of the formation of complexes. Complex formations were also detected when the alcohol was replaced by phenyl isocyanate. Significantly larger concentrations of the catalyst were involved in isocyanate complexes than were shown to be the case with the alcohol complexes. These results appear to be experimental evidence for the previously proposed ternary complex as an intermediate in the metal‐catalyzed formation of urethanes.
Catalytic action of metallic salts in autoxidation and polymerization. IV. Polymerization of methyl methacrylate by cobalt(II) or (III) acetylacetonate–tert‐butyl hydroperoxide or dioxane hydroperoxide
Authors: Osawa Zenjiro , Shibamiya Tetsuaki , Kawamata Toshio 
Published: April 2003

AbstractPolymerization of methyl methacrylate was carried out by four initiating systems, namely, cobalt(II) or (III) acetylacetonate–tert‐butyl hydroperoxide (t‐Bu HPO) or dioxane hydroperoxide (DOX HPO). Dioxane hydroperoxide systems were much more effective for the polymerization of methyl methacrylate than tert‐butyl hydroperoxide systems, and cobaltous acetylacetonate was more effective than cobaltic acetylacetonate in both hydroperoxides. The initiating activity order and activation energy for the polymerization were as follows: Co(acac)2–DOX HPO (Ea‐9.3 kcal/mole) > Co (acac)3–DOX HPO (Ea = 12.4 kcal/mole) > Co(acac)2–t‐Bu HPO (Ea = 15.1 kcal/mole) > Co(acac)3–t‐Bu HPO (Ea‐18.5 kcal/mole). The effects of conversion and hydroperoxide concentration on the degree of polymerization were also examined. The kinetic data on the decomposition of hydroperoxides catalyzed by cobalt salts gave a little information for the interpretation of polymerization process.
Radiation‐induced polymerization of isobutylene oxide
Authors: Bauer R. S. , Spooncer W. W. 
Published: April 2003

AbstractIn the absence of oxygen, liquid isobutylene oxide is polymerized by high energy radiation. The resultant polyethers may possess the same gross structures as those prepared by Lewis acid catalysis:
magnified image
The reaction is characterized by (1) a small, apparent activation energy (2.7 kcal/mole), (2) a polymerization rate proportional to the first power of the dose rate, (3) inhibition by Lewis bases, and (4) moderate inhibition by free‐radical scavengers. The molecular weights of the polymers increase with decreasing temperatures of polymerizations. These results will be discussed in terms of a cationic propagation mechanism.
Studies on the polymerization of ethyl acrylate. III. Effect of temperature on the solvent‐transfer reaction
Authors: Raghuram P. V. T. , Nandi U. S. 
Published: April 2003

AbstractThe effect of temperature on transfer constants for different solvents in the polymerization of ethyl acrylate was observed. Activation energy differences (EtrS − Ep) and frequency factors were computed. It is observed that high frequency factors are associated with high activation energies. Values of EtrS were calculated by an approximate method and were compared with the available data on methyl methacrylate, isobutyl methacrylate, and styrene.
Structure–property relationships of ring‐containing nylon 66 copolyamides
Authors: Ridgway James S. 
Published: April 2003

AbstractSeveral series of nylon 66 copolyamides were prepared with up to 30 mole‐% substitution of ringed comonomers of the type X‐(CH2)n‐R‐(CH2)n‐X, wheren= 0, 1, or 2; X = −NH2or CO2H; and R = phenylene, cyclohexylene, or naphthyle. The ring structure was correlated with glass transition temperature and melting point. The important features of ring structure fall into the following categories: ring isomerism, aromaticity, diamine vs. diacid substitution, chain length, and ring substitution. Proper “fit” (isomorphism) of the comonomer into the nylon 66 chain appears to be the main criterion for ringed copolymers of highTgand high melting point.
Reactivity ratios and copolymerization parameters for copolymers incorporating n‐octadecyl acrylate and N‐n‐octadecylacrylamide
Authors: Jordan Edmund F. , Bennett Richard , Shuman Andrea C. , Wrigley A. N. 
Published: April 2003

AbstractMonomer reactivity ratios and copolymerization parameters were determined for n‐octadecyl acrylate and N‐n‐octadecylacrylamide with several monomers not previously reported. Values of Q and e for the long‐chain acrylate now agreed more closely than before with the average of values for the lower acrylate homologs. The average polarity parameter for N‐n‐octadecylacrylamide still showed more electron withdrawal from the double bond (e = 0.42) than was expressed by the average literature value (e = −0.10) for N‐n‐octylacrylamide. Because penultimate effects were absent in this work, the reason for the discrepancy seems to reside in the copolymer analysis. Reactivity ratios for oleyl and octadecyl acrylate with methyl methacrylate were similar. Coefficients for the relation between overall rates of copolymerization and composition were obtained on some systems by curve fitting with a computer. They generally showed a slight minimum.
Polymers containing anthraquinone units: Polymers from 1,2,5,6‐tetraaminoanthraquinone
Authors: Bracke William , Marvel C. S. 
Published: April 2003

AbstractA preparation for 1,2,5,6‐tetraaminoanthraquinone was worked out. The reactivity of this compound in nucleophilie substitutions and nucleophilic additions was studied. Polymers were made by condensation with pyromellitic anhydride, terephthaloyl chloride, and isophthaloyl chloride. The synthesis and properties of the corresponding model compounds are also reported. After reduction with sodium dithionite, the polymers are soluble in dimethylformamide–water mixtures.
Benzimidazole, benzothiazole, and benzoxazole polymers with anthracene recurring units
Authors: Kokelenberg Hendrik , Marvel C. S. 
Published: April 2003

AbstractIn an attempt to prepare polymers which might be oxidized to compounds soluble in alkali diphenyl 1,5‐anthracenedicarboxylate was reacted with diaminobenzidine, dimercaptobenzidine, and diaminobiphenol in the melt and with dimercaptobenzidine dihydrochloride in polyphosphoric acid. Compounds of high molecular weight were obtained and their thermal and oxidative stability evaluated. Model compounds were prepared and their ultraviolet spectra compared with those of the polymers. Oxidation with nitric acid or chromium trioxide yielded some anthraquinone derivatives, but side reactions prevented the formation of useful products.
Depolymerization of polysulfide polymers by dithionite ions
Authors: Rekalic Vladimir J. , Radosavljević Slobodan D. , Tenc‐Popović Mirjana E. 
Published: April 2003

AbstractThe action of sodium dithionite, Na2S2O4 on desulfurized tetrasulfide polymers leads to their depolymerization. Our studies showed that successful depolymerization can be initiated only in an alkali medium when 1.9–3.2 mole of sodium hydroxide per mole of dithionite is used, and that this leads to the cleavage of disulfide bonds and the formation of polymers of lower molecular weight with SH end groups. Liquid polymers of 1000–5000 molecular weight are obtained when 0.388–0.155 mole sodium dithionite per segment of polymer is used for depolymerization in the presence of the above‐mentioned quantity of sodium hydroxide per mole of dithionite. The depolymerization of poly‐sulfide polymers with sodium dithionite in the presence of sodium hydroxide was followed by determination of the molecular weight and sulfur content of the polymer and analysis of the mother liquid.
Participation of an excited monomer in the propagation reaction of the γ‐ray induced polymerization of ethylene
Authors: Hagiwara Miyuki , Okamoto Hidemasa , Kagiya Tsutomu 
Published: April 2003

AbstractIn the polymerization of ethylene, the reactivity of the growing radical produced by γ‐radiation was compared with that of the radical from 2,2′‐azobisisobutyronitrile. The radicals produced in the polymerization at around room temperature were long‐lived irrespective of the method of initiation. However, it was found that the radical produced by γ‐radiation became unreactive to ethylene when the reaction system was not exposed to γ‐rays. Irradiation with γ‐rays or ultraviolet light in a region below about 3900 Å was required for its chain growth. On the other hand, the radical from AIBN was always reactive, and the reactivity was little changed by γ‐radiation or by the presence of a trace amount of radiolysis products of ethylene. In explaining of these characteristic differences between the nature of these radicals produced by two different methods of initiation, some other information on their reactivity was reviewed, and the participation of an excited ethylene in a dimer form was proposed, as for the propagation reaction of the γ‐ray‐induced polymerization.
Electroinitiated cationic polymerization of styrene
Authors: Funt B. L. , Blain T. J. 
Published: April 2003

AbstractA constant controlled current was passed through a solution of styrene in methylene chloride containing a tetraalkylammonium salt as supporting electrolyte. Reproducible rates of polymerization were initiated by the electrochemical techniques employed and the kinetics of the reaction were investigated. Sigmoidal curves of conversion versus time were observed. A kinetic relationship of the form In ([M0]/[M]) = ½ Kt2 was derived on the basis of simple assumptions regarding the mechanism and fitted the data accurately. The rate constants obtained were compared to others reported, and the influences of ion association on the values of the rate constants obtained are discussed. The reactions were decreased in rate by a reversal of polarity of the electrodes. However, the stoichiometry of the production of active centers and of their destruction was not ideal, in that each electron did not result in the initiation of a polymer chain.
Mechanism of charge–transfer polymerization. II. Propagation mechanism of the polymerization of N‐vinylcarbazole with organic electron acceptors
Authors: Fujimatsu Masaaki , Natsuume Tadao , Hirata Hirotaka , Shirota Yasuhiko , Kusabayashi Shigekazu , Mikawa Hiroshi 
Published: April 2003

AbstractCopolymerizations of N‐vinylcarbazole with both isobutyl vinyl ether and N‐vinyl‐pyrrolidone initiated by some organic electron acceptors have been investigated for the purpose of elucidating the propagation mechanism in the charge‐transfer polymerization. Copolymerizations of the same system catalyzed by authentic cationic catalysts have also been made for comparison. The results indicate that the propagation mechanism of the charge‐transfer polymerization studied is catio ie.
Copolymerization of styrene and butadiene in emulsion. I. Composition of the latex particles
Authors: Burnett G. M. , Cameron G. G. , Thorat P. L. 
Published: April 2003

AbstractThe composition of the latex particles during intervals I and II of the emulsion polymerization of styrene and butadiene (initial weight ratio 71 parts butadiene:29 parts styrene) has been determined at 5, 15, and 25°C. The monomer content of the latex particles diminishes linearly with conversion. The composition ratio (weight styrene: weight butadiene inside the particles divided by weight styrene:weight butadiene in the binary phase) also decreases with conversion, the decrease being particularly marked as the end of interval II is approached. It is shown that the assumptions embodied in the theory of Medvedev et al. are incorrect. The results are compared with the recent theories of Gardon.
Isomorphic interactions of ethylenic polymers and paraffin wax
Authors: Tordella J. P. , Dunion P. F. 
Published: April 2003

AbstractThe high degree of flexibility of blends containing minor amounts of partly crystalline copolymers of ethylene and vinyl acetate in paraffin wax seems to be a manifestation of some type of interaction. Low‐angle x‐ray diffraction of such blends showed a new long spacing intermediate in length between the polymer long spacing and the c axis length of the wax unit cell. This new long spacing appears to be a consequence of isomorphism involving cocrystallization of polymeric ethylene sequences and wax molecules. A lesser type of isomorphic interaction, epitaxy, occurs in polyethylene–wax blends: wax overgrows crystals of already crystallized polyethylene in the same orientation without a change in its c axial dimension.
Effect of molecular structure on polyethylene melt rheology. II. Shear‐dependent viscosity
Authors: Mendelson R. A. , Bowles W. A. , Finger F. L. 
Published: April 2003

AbstractThe investigation of the effect of molecular structural variables on the melt viscosity of polyethylene was extended to the shear dependent region by application of a reduced variables treatment following, in a formal sense, that of Bueche. Viscosity–shear rate data were obtained for a series of experimentally polymerized linear polyethylene samples having a range of molecular weights and molecular weight distributions as characterized primarily by gel permeation chromatography. These data could be superimposed on a single reduced variables flow curve using parameters which were a function only of temperature, limiting Newtonian viscosity, M̄w, and M̄w/M̄n. The same treatment was successfully applied also to branched (low‐density) fraction data discussed in a previous paper, with additional correction for long‐chain branching. However, different reduced variables curves were obtained for the branched and linear cases.
Melting behavior of linear polyethylene crystallized by solution stirring
Authors: Rijke A. M. , Mandelkern L. 
Published: April 2003

AbstractCalorimetric and dilatometric studies have been made of the fusion process of linear polyethylene crystals precipitated by high speed stirring from solution. It is shown that long‐time annealing at elevated temperatures alleviates the superheating observed when rapid heating rates are employed. By the annealing procedures that have been adopted, a small but demonstrable fraction of high melting material can be produced whose melting temperature depends on the crystallization temperature. For crystallization at 105°C, followed by annealing at 142°C, a melting temperature of 146.0 ± 0.5°C is observed. The dissolution temperature in xylene, determined for the same sample, is consistent with the high melting temperature observed for the pure polymer. It is recognized that a state of high axial orientation need not necessarily be identified with extended chain crystals. Consequently, the increased melting temperature can result from either an increase in the crystallite size or a reduced interfacial free energy relative to crystallites produced by the more conventional mode of crystallization.