bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron spin resonance study of polymerization of butadiene with tris(acetylacetonato)titanium and triethylaluminum
Authors: Hiraki Katsuma , Inoue Takeo , Hirai Hidefumi 
Published: April 2003

AbstractESR spectra of homogeneous catalyst derived from tris(acetylacetonato)titanium(III) and triethylaluminum were observed at several temperatures from −78°C, to +25°C, at molar ratios of aluminum to titanium of 1–108. At −78°C, this catalyst yields a violet complex which shows an ESR signal with a g value of 1.959 and is associated with the first intermediate. At −40°C to −30°C, this signal decreases, and two signals with g values of 1.947 and 1.960 are observed. The latter two signals diminish at −5°C to +10°C, while two kinds of new signals with g values of 1.965 and 1.969 appear overlapping each other. The structures of the species corresponding to these five signals are discussed on the basis of the ESR spectra, the intensity change, and the unpaired spin distribution. A new signal with a g value of 1.978 is found in the presence of butadiene at 25°C at Al/Ti > 8 and is assigned to a growing end of polybutadiene with this catalyst. The polymer yield increases remarkedly at Al/Ti molar ratios greater than 10. The microstructure of the resulting polymer consists almost completely of 1,2 units. The structure of the growing end is proposed to be a titanium (III) species containing two 1‐substituted allyl groups, by comparison with the structure ascribed to the growing end of polybutadiene with n‐butyl titanate‐triethylaluminum catalyst.
The reaction between diethyl succinylsuccinate (1,4‐diethoxycarbonyl‐2,5‐dihydroxy‐1,4‐cyclohexadiene) and amines and its application to polymer synthesis
Authors: Higashi Fukuji , Tai Akira , Adachi Kazuo 
Published: April 2003

AbstractPolymers having polyamine structures were obtained by the condensation reaction between diethyl succinylsuccinate (1,4‐diethoxycarbonyl‐2,5‐dihydroxy‐1,4‐cyclohexadiene) and aliphatic diamines. The reactions were carried out in high polar solvents such as N‐methylpyrrolidone (NMP) and N,N‐dimethylformamide (DMF). The mode of the polymerization reaction and the structure of the polymers were verified by studies of model compounds. The polymers thus obtained were conveniently utilized as coating and adhesive materials and were able to be cast into films.
Polymerization and crosslinking of epoxides: Base‐catalyzed polymerization of phenyl glycidyl ether
Authors: Banks P. , Peters R. H. 
Published: April 2003

AbstractThe anionic polymerization of 2,3‐epoxypropyl phenyl ether initiated by sodium methoxide and dimsyl sodium in dioxane and in dimethyl sulfoxide has been studied. Kinetic and dielectric constant measurements have been recorded, and a mechanism for the initiation reaction with dimsyl sodium has been put forward. Polymerization initiated with dimsyl sodium revealed almost total absence of sulfur in the polymer by endgroup analysis. The reaction was shown to be inhibited by oxygen. Molecular weight determinations have indicated a reaction involving transfer to give polymers of lower than calculated M̄n and a ratio of kp/ktr ratio of approximately 73. Gel‐permeation chromatography suggests a narrow molecular weight distribution in the polymers prepared.
A study on the mechanism of polyvinyl chloride stabilization by lead salts
Authors: Zilberman E. N. , Kulikova A. E. , Meiman S. B. , Okladnov N. A. , Lebedev V. P. 
Published: April 2003

AbstractInfrared spectroscopic and DTA measurements and chemical analysis have shown that during stabilization of PVC with organic and inorganic basic lead salts various reactions occur: (a) binding of the evolved HCl, by these salts with the formation of lead chloride and complexes, including HCl, which catalyze the PVC degradation; (b) complex‐forming reaction with the reactive PVC groups, which decreases the intensity of color of the polymer. In addition, with weak‐organic‐acid basic lead salts, exchange of labile Cl atoms for acid residues in PVC occurs, which results in an increase in inherent polymer stability.
Thermal degradation of copolymers of styrene and acrylonitrile. II. Reaction products
Authors: Grassie N. , Bain D. R. 
Published: April 2003

AbstractHydrogen cyanide is a minor product of degradation of copolymers of styrene and acrylonitrile. The liquid products have been separated and identified by combined gas chromatography and mass spectrometry (GC‐MS), as styrene, acrylonitrile, toluene, and benzene. The ratio of styrene to acrylonitrile monomers in the products is approximately twice that of the monomer units in the copolymers, and the ratios of styrene to toluene and benzene are the same as are obtained from pure polystyrene. These ratios were determined by using infrared spectral methods. The fraction of products volatile at the temperature of degradation but involatile at ambient temperature was also analyzed by using GC‐MS. A series of four dimers and four trimers were fairly reliably identified. The residual material from copolymers containing up to 33.4% acrylonitrile is always soluble in toluene. The 50/50 copolymer and its residues are insoluble in toluene. Yellow coloration develops in the residues from high acrylonitrile copolymers at advanced stages of degradation. Infrared and ultraviolet spectra suggest that this is due to conjugated unsaturation in the polymer chain backbone which may be associated with the liberation of hydrogen cyanide from the acrylonitrile units.
Thermal degradation of copolymers of styrene and acrylonitrile. III. Chain‐scission reaction
Authors: Grassie N. , Bain D. R. 
Published: April 2003

AbstractThe chain‐scission reaction which occurs in copolymers of styrene and acrylonitrile has been studied at temperatures of 262, 252, and 240°C. Under these conditions volatilization is negligible, and chain scission can be studied in virtual isolation. At 262°C three kinds of chain scission are discernible, namely, at weak links which are associated with styrene units, “normal” scission in styrene segments of the chain and scission associated with the acrylonitrile units. The rate constants for normal scission and scission associated with acrylonitrile units are in the ratio of approximately 1 to 30. The molecular weight of the copolymer has no effect on the rates of scission. At 252°C the same general behavior is observed for the copolymers containing up to 24.9% acrylonitrile. The 33.4% acrylonitrile copolymer is anomalous, however. At 240°C the trends observed at 262°C appear to break down completely although individual experiments are quite reproducible. This behavior at the lower temperatures is believed to be associated with the fact that the melting points of the various copolymers are in this temperature range. Thus the viscosity of the medium, which should be expected to have a strong influence on the chain scission reaction, will be changing rapidly with temperature, copolymer composition, and molecular weight in this temperature range.
Molecular weight development in constant‐rate styrene emulsion polymerization
Authors: Grancio M. R. , Williams D. J. 
Published: April 2003

AbstractContinuously uniform latices were applied in an experimental study of molecular weight development in constant‐rate styrene emulsion polymerization. The formulation around which this study centered exhibited Smith‐Ewart, case II kinetics from zero to about 60% conversion with a constant conversion rate of 13 ± 2%/hr and a final particle diameter of 2300 Å. By utilizing an inhibitor perturbation technique, we directly confirmed that free radicals are generated from K2S2O8 by a first‐order process with 100% efficiency. We further confirmed that, in contrast to current theories for constant rate polymerization, both the instantaneous values of M̄n and M̄v may increase 6‐ to 9‐fold. Little or no chain branching is evidenced. We interpret these findings to mean that radicals are not utilized with 100% efficiency in emulsion polymerization.
Poly‐2‐oxazolidones: Preparation and characterization
Authors: Herweh J. E. , Whitmore W. Y. 
Published: April 2003

AbstractPoly‐2‐oxazolidones were synthesized by the 1,3‐cycloaddition of bisglycidyl ethers to diisocyanates with the use of N,N‐dimethylformamide and lithium chloride as solvent and catalyst, respectively. A variety of arylene and alkylene diisocyanates and coreactant bisepoxides were used in the polymer‐forming reaction. The polymers, obtained in high yield, were generally soluble in methylene dichloride, chloroform, N,N‐dimethylformamide, and dimethyl sulfoxide. They had intrinsie viscosities up to 0.42 dl/g and could be cast into films. In several cases molecular weights were determined by vapor pressure osmometry. The poly‐2‐oxazolidone based upon 1,6‐hexamethylene diisocyanate and the bisglycidyl ether of isopropylidene diphenol gave the highest molecular weight. Confirmation that the base unit of the polymers contains the 2‐oxazolidone ring was obtained by elemental analysis, infrared and NMR spectroscopy. The poly‐2‐oxazolidones synthesized were found to be amorphous by x‐ray diffraction. Thermogravimetric analyses indicated that a majority of the poly‐2‐oxazolidones were stable in dry air up to 300°C. In a number of cases Tg's were also determined by using differential scanning calorimetry.
Polymerization of vinyl monomers by diphenylsulfone–potassium complexes
Authors: Hirahara Takuji , Sugimura Takaaki , Minoura Yuji 
Published: April 2003

AbstractDiphenylsulfone (DPSO2) was found to react with an equimolar amount of potassium in tetrahydrofuran (THF), dimethoxyethane (DME), or diglyme (DG) at reflux or an elevated temperature to yield a reddish‐black solution, giving an electron spin resonance (ESR) signal. The signal was attributed to the formation of relatively labile DPSO2 anion radical. The apparent effects of solvents on the reactivity of DPSO2 with potassium depended on the polarities and the solvation powers: benzene ≅ toluene ≅ dioxane ≪ tetrahydrofuran < monoglyme < diglyme. The monopotassium complex was found to react further with another molecular amount of the metal to yield a dark blue solution giving no ESR signal.The monopotassium complex initiated the polymerization of acrylonitrile (AN). It did not, however, initiate the polymerization of methyl methacrylate (MMA), styrene (St), or isoprene (IP). The active species of the monopotassium complex that initiated the polymerization of AN was found from analyses of the reaction products and the infrared spectrum of oily oligomer of AN obtained by the complex to be potassium benzenesulfinate. The dipotassium complex was found to initiate the polymerization of MMA, St, IP and AN. The active species of the dipotassium complex that initiated the polymerization of MMA, St, or IP was found from analyses of the reaction products and the infrared spectrum of the oily oligomer of MMA obtained by the complex to be phenyl potassium.
Calorimetric investigation of polymerization reactions. IV. Curing reaction of polyester fumarate with styrene
Authors: Horie Kazuyuki , Mita Itaru , Kambe Hirotaro 
Published: April 2003

AbstractThe curing reaction of polyester fumarate with styrene was investigated with a differential scanning calorimeter (DSC) operated isothermally. The change in rate of cure was followed over the whole range of conversion. The rate of cure is accelerated by the gel effect to about ten to fifty times the rate of model copolymerization of diethyl fumarate with styrene. This autoacceleration is much enhanced for systems with higher crosslinking densities and at lower temperatures. The results confirm that both termination and propagation steps of the curing reaction are controlled by diffusion of polymeric segments and monomer molecules over almost the whole range of conversion. The final extent of conversion is short of completion for isothermal cure and even for postcure of polyester fumarate with styrene because of crosslink formation. The final conversion of isothermal cure decreases with increasing crosslinking density and shows a maximum with increasing reaction temperature. This temperature dependency of the final conversion is caused by the difference in the activation energies for two propagation rate constants kpf and kps, which were evaluated to be 7–10 and 5–8 kcal/mole, respectively, for the intermediate stage of the curing reaction.
Studies on polyesterification reactions: Calculation of the rates of reverse reactions
Authors: Vancsó‐Szmercsányi I. , Makay‐Bödy E. , Szabó‐Réthy E. , Hirschberg P. 
Published: April 2003

AbstractReactions between dicarboxylic acids and diols in the melt and leading to an equilibrium yield quantitative results which may be applied to the kinetics of some partial reactions of polyesterification. The relationship of the rate constants of the forward and the reverse reaction as well as of the equilibrium constant furnish valid results both in the absence of catalyst and in the presence of acid or basic catalysts. The values obtained for the energy of activation of the forward and the reverse reaction and of the overall reaction (13 ± 1 kcal/mole) also are in good agreement.
Polymérisation et copolymérisation cationiques des methylindenes
Authors: Maréchal Ernest 
Published: April 2003

AbstractA study of cationic polymerization and copolymerization of methylindenes has been carried out by experimental methods and by means of quantic chemistry. The study showed a great variation among initiators in efficiency for the various monomers. The study of the effect of temperature on polymerization was carried out for dimethyl‐5,7‐indene. Polymerization enthalpies and reactivity ratios were determined; the values that were obtained allowed a classification of methylindenes with regard to their reactivity toward a single cation. Total electron densities, free valences, and mobile bond orders, frontier electron densities, and superdelocalizabilities on position 1 and 2 were calculated for all methylindenes. In determining location energies of the electronic double bond in position 2 and the stabilization energies at the time of the attack by a cation, a theoretical classification of the monomers with respect to their reactivity in cationic polymerization was obtained. The agreement between calculation and experimental results is shown to be satisfactory.
Mechanism of the polymerization of trifluoroacetaldehyde initiated by azobisisobutyronitrile
Authors: Busfield W. K. , Humphrey R. W. 
Published: April 2003

AbstractThe polymerization of fluoral initiated by the photolyzed decomposition of azobisisobutyronitrile at low temperature has been studied. Up to 2% conversion, the effect of radical scavengers and the order with respect to initiator and light intensity indicate that the reaction occurs by a conventional radical polymerization mechanism. At about 2% conversion autoacceleration sets in and the rates become irreproducible. This is explained by typical occlusion phenomena. Tracer studies show that polymer prepared at high conversion contains initiator fragments indicating that primary propagation is by monomer addition to radicals. The reaction mechanism is discussed.
Prehump in the gel‐permeation chromatography fractionation of pulp cellulose acetate
Authors: Tanghe L. J. , Rebel W. J. , Brewer R. J. 
Published: April 2003

AbstractGPC chromatograms of cellulose acetate made from wood pulp customarily show a shoulder or small separate peak at the high end of the DP distribution. Material isolated from this “prehump” area is considerably enriched in mannose and xylose, and the size of the prehump in acetates from different pulps correlates with the amount of hemicellulose in the pulp. Prehump is not ordinarily found in cellulose acetate made from linters but was induced by adding mannan at the start of the acetylation, or by prolonging the acetylation beyond the time when the cellulose acetate sulfate triester is first formed. Products of poor solubility, as indicated by increased haze and false viscosity, resulted in both cases. Prehump was reduced in pulp cellulose acetate by many of the steps which give products of improved solubility: mercerization of cellulose prior to acetylation, use of more sulfuric acid catalyst, replacement of part of the acetic acid with methylene chloride during acetylation, and by removal of a small amount of high viscosity or poorly soluble material by fractional precipitation.
Polymerization ofcis‐ andtrans‐cinnamonitriles by anionic catalysts
Authors: Kobuke Yoshiaki , Fueno Takayuki , Furukawa Junji 
Published: April 2003

Abstractcis‐ andtrans‐cinnamonitriles were polymerized in the presence of various anionic catalysts such as Grignard reagent, alkali metal naphthalenes, and calcium zinc tetraethyl. It was found that both monomers undergo concurrent geometrical isomerization as well as polymerization. Investigation on the calcium zinc tetraethyl catalyst showed that thetrans‐nitrile had polymerizability noticeably greater than that of thecisisomer. Polymers resulting from these isomeric monomers had different microstructures. These results seem to be interpretable in terms of the four‐centered coordination model of the transition state.
Production of organometallic polymers by the interfacial technique. X. Influence of the nature of base employed on the synthesis of polysilylalkylene (arylene) diamines
Authors: Carraher Charles E. 
Published: April 2003

AbstractThe influence of base type on polymerization and on polymer properties in the synthesis of polysilylalkylene(arylene)diamines by a modified interfacial system was investigated. The modified system utilizes 2,5‐hexanedione or acetonitrile in place of the usual aqueous solvent. Protonation of both diamine and amine groups in the polymer chain is important when NaOH or diamine itself is employed as the base. Protonation is unimportant when triethylamine is used. In triethylamine systems the highest yield is formed with the silane containing the most electron‐deficient silicon, and the highest molecular weight products are formed with the least sterically hindered silane. When NaOH or diamine itself is employed there is no apparent correlation between silane and amine electronic or steric nature and any of the measured polymer properties. As diamine solubility decreases, polymer yield increases.
Self‐regulating polycondensations: Ordered aromatic polyamide‐esters
Authors: Preston J. 
Published: April 2003

AbstractThe polycondensation of aminophenols with diacid chlorides was examined to determine if the amide‐ester polymers obtained are random or ordered. All of the evidence obtained points to the conclusion that ordered copolymers indeed are prepared and that a “self‐regulating” polymerization process is operating by virtue of the considerably greater reactivity of aromatic amino groups relative to phenol groups. The first step of the reaction involves the in situ preparation of a diphenol‐amide which undergoes further condensation. The diphenol‐amide intermediate may be isolated or reacted in situ. In addition to the ordered polymer from a given aminophenol and a single diacid chloride, ordered copolymers from two different diacid chlorides were prepared in which the diacid moieties appear in an alternating fashion; the structure of such polymers depends on the order of addition of the diacid chlorides. Corresponding polymers also may be prepared from the preformed diphenol‐amide monomers. The molecular weights of certain of the polymers were sufficient for the preparation of films which could be hot‐stretched severalfold. Interfacial polycondensations gave polymers of higher inherent viscosities than did solution polymerizations when aminophenols or diphenol‐amide monomers were condensed with diacid chlorides.
Photo‐oxidation of polymers without light: Oxidation of polybutadiene and an ABS polyblend with singlet oxygen
Authors: Kaplan M. L. , Kelleher P. G. 
Published: April 2003

AbstractIn recent years much evidence has been accumulated to implicate electronically excited oxygen (1Δg) molecules as the agent responsible in photosensitized oxidations for the formation of allylic hydroperoxides from olefins and of endoperoxides from 1,3‐dienes. Little regarding the mechanistic aspects of the photo‐oxidative degradation of polybutadiene (PBD) is known, however. To determine if electronically excited oxygen (1Δg) molecules can oxidize PBD, the ABS polyblend and standard samples of PBD's containing high trans, high cis, and high vinyl content were treated in homogeneous solution at low temperature with chemically produced singlet oxygen in situ. The source of the singlet oxygen was the triphenylphosphite‐ozone adduct. Studies by spectroscopy, elemental analysis, viscosity determinations, and gel measurements showed only the cis‐ and the trans‐PBD were susceptible to oxidation; no chain scission was involved in the attack of cis‐ and trans‐PBD by singlet oxygen; the oxidation of the cis PBD involved the initial formation of hydroperoxides which on thermal decomposition yielded gel. The trans‐PBD was found to oxidize but apparently by a mechanism different from that of cis‐PBD. Initial singlet oxygen attack of ABS proceeds by oxidation of the PBD portion of the polyblend. It was also observed that when only a small amount of the double bonds in the cis‐PBD polymer had been oxidized to hydroperoxides, subsequent thermal treatment of this sample resulted in gross structural changes in the whole polymer.
Polymers containing anthraquinone units: Polycondensations 1,2,5,6‐tetraaminoanthraquinone with some tetrachloroquinoxaline compounds
Authors: Banihashemi A. , Marvel C. S. 
Published: April 2003

AbstractNew ladder and partial ladder aromatic heteropolymers have been synthesized from 1,2,5,6‐tetraaminoanthraquinone, 2,3,7,8‐tetrachloro‐1,4,6,9‐tetraazaanthracene, 2,2′‐3,3′‐tetrachloro‐6,6′‐diquinoxaline, 2,2′,3,3′‐tetracholoro‐6,6′‐diquinoxalyl ether and 2,2′,3,3′‐tetrachloro‐6,6′‐diquinoxalyl sulfone. The polycondensations were carried out in solution and in melt. The inherent viscosities of polymers were in the range of 0.1‐0.44. These polymers were highly colored, showed good thermal stability and were soluble in concentrated sulfuric acid and methanesulfonic acid. The structures of the polymers were established by comparison with model compounds.
Copolymerization of aryldiazomethanes
Authors: Smets G. , Bourtembourg A. 
Published: April 2003

AbstractSeveral aryldiazoalkanes (M2) have been copolymerized with phenyldiazomethane (M1) in toluene‐methanol solution at 40°C, namely, the p‐chloro‐, p‐methoxy‐, p‐mesyl‐o and ‐p‐methyl‐, 2,4‐ and 3,4‐dichlorophenyldiazoalkanes, and the α‐ and β‐ naphthyl‐diazoalkanes. The copolymerization parameters r1 and r2 have been evaluated. By plotting 1/r1 against the Hammett σ values a negative ρ values was found equal to −0.88. From cationic copolymerizations carried out at −78°C in the presence of boron trifluoride‐diethyl ether as catalyst a similar plot of 1/r1 against σ gives a value of ρ equal to −0.82. The negative sign and the agreement between these ρ values demonstrates the cationie mechanism of the methanol polymerization and copolymerization of aryldiazoalkanes.