bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR studies on the stereospecific polymerization of methyl vinyl ether. Part II. Polymerization by sulfuric acid–aluminum sulfate complex: Enantiomorphic catalyst sites model
Authors: Higashimura T. , Ohsumi Y. , Kuroda K. , Okamura S. 
Published: April 2003

AbstractHighly crystalline poly(methyl vinyl ether) (PMVE) was produced in toluene in a temperature range of 0 to −20°C. with the use of sulfuric acid–aluminum sulfate complex (SA catalyst). It was found from the NMR spectra that these polymers contained more than 50% of the triad isotactic fraction and the melting point of the unfractionated polymer was about 130°C. However, PMVE containing a large amount of the isotactic fraction was insoluble in nitromethane, so the triad tacticity of highly crystalline PMVE could not be quantitatively determined. The molecular weight of PMVE increased with increasing conversion and increasing polymerization temperature. This behavior is different from that in metal halide catalysts. Also, the stereoregularity of PMVE decreased with increasing monomer concentration. However, addition of a polar solvent and increasing the polymerization temperature had little effect on the stereoregularity of the polymer. The increase in the isotactic fraction at high catalyst concentration and the difference in the monomer composition in the copolymerization of methyl vinyl ether with 2‐chloroethyl vinyl ether by SA catalyst from that obtained by BF3·O(C2H5)2 suggest that the absorption of MVE on a catalyst surface is an important step in the propagation step by SA catalyst. The fraction of the triad tacticity calculated from the enantiomorphic catalyst sites model8 coincided with the experimental results. This fact shows that the steric structure of the adding monomer is determined only by the nature of the catalyst irrespective of the nature of a growing chain end. It is concluded, on considering also the results of the previous paper, that completely different factors can control the steric structure of a polymer even for the same monomer when different catalysts are used.
Pulse radiolysis studies of styrene
Authors: Metz D. J. , Potter R. C. , Thomas J. K. 
Published: April 2003

AbstractWe have applied the pulse radiolysis technique of studying short‐lived, radiation‐produced intermediates to a study of pure, dry liquid styrene. We have observed at least three distinct species. The most rapidly decaying species (τ1/2 = 4 μsec., λmax ≈ 370 mμ) exhibits an apparent first‐order decay which is slowed down in the presence of dry oxygen, occurs too rapidly to be measured in the presence of water, and has a temperature coefficient of approximately 1 kcal./mole between 25 and 45°C. We have tentatively identified the species as the styryl anion with a G value for formation of approximately 0.15. A second species (τ1/2 = 220 μsec. λmax ≈ 320–330 mμ) exhibits a first‐order decay which appears to be independent of oxygen and water. From its spectrum, we have tentatively identified it as the styryl radical. The third species (λmax ≈ 310 and 320 mμ) is relatively stable in the dark, but is radily photolyzed by the analyzing light of the usual experimental set‐up for pulse radiolysis studies. The formation of this species appears to be independent of the water and oxygen content of the styrene.
Polymerization of β‐isovalerolactone
Authors: Ciaperoni A. , Gechele G. B. , Mariani L. 
Published: April 2003

AbstractThe polymerization of β,β′‐dimethyl‐β‐propiolactone with various catalysts was investigated. A detailed study on the heterogeneous polymerization initiated by triethyl aluminum was carried out. A reaction mechanism is suggested on the basis of chemical analysis of the polymer.
Polymerization of aromatic nuclei. XII. Oligomerization of halobenzenes by aluminum chloride‐cupric chloride
Authors: Kovacic Peter , Uchic John T. , Hsu Li‐Chen 
Published: April 2003

AbstractPolymerization of chloro‐ and fluorobenzene by aluminum chloride‐cupric chloride produced highly colored oligomers. Chlorobenzene reacted under the standard conditions, i.e., 6/1/0.5 (molar ratio) of aromatic/catalyst/oxidant at 60°C. for 1 hr., to give a red solid in 14% yield. Evidence concerning the structure was obtained from elemental analyses, infrared and ultraviolet spectra, dechlorination, oxidation, solubility, molecular weight, and color. The data indicate that the backbone chain consists of an o‐polyphenyl structure with chlorine atoms situated at the 4‐positions. Polynuclear regions presumably comprise part of the structure. Molecular weight data pointed to an average of 10–12 units per chain. The coupled product from fluorobenzene was very similar to the chlorobenzene oligomer in most respects. In contrast to the chlorobenzene case, there was evidence of propagation occurring to some extent by attack ortho to the fluorine. Bromobenzene produced brominated p‐polyphenyl apparently by disproportionation to benzene which then functioned as the monomer. An oxidative cationic mechanism (σ polymerization) is proposed for the nuclear coupling.
Polybenzimidazoles. VI. Polybenzimidazoles containing aryl sulfone linkages
Authors: Narayan T. V. Lakshmi , Marvel C. S. 
Published: April 2003

AbstractFour new polybenzimidazoles with aryl sulfone linkages between the recurring units have been prepared in order to study their thermal stability and solubility properties. The polymers prepared were high molecular weight materials with good thermal stability.
Synthesis of polyamides by the polyaddition of bisimidazoline with dicarboxylic acids
Authors: Kagiya Tsutomu , Izu Masatsugu , Hatta Masakazu , Matsuda Takehisa , Fukui Kenichi 
Published: April 2003

AbstractN,N′‐Dipropionylethylenediamine was synthesized by the ring‐opening addition reaction of 2‐ethyl‐2‐imidazoline with propionic acid at 220°C. By applying this reaction to polymerization, polyamides were synthesized by the ring‐opening polyaddition reaction at 220°C. of 1,4‐bis(imidazoline‐2‐yl)butane with adipic acid, succinic acid, sebacic acid, and terephthalic acid. The reaction product of 1,4‐bis(imidazoline‐2‐yl)butane with adipic acid, which was proposed to be nylon 26, was compared with an authentic sample of nylon 26 and shown to possess a very similar infrared spectrum and melting point.
Xylene‐stream method for obtaining thin polyethylene specimens for electron microscopy
Authors: Kubota Katsuya 
Published: April 2003

AbstractA new technique is described for obtaining thin specimens from melt‐crystallized polyethylene surface for studying the lamellar structure with the electron microscope. The specimen was first backed with carbon–gelatin backing and then the polyethylene side was exposed to a temperature‐controlled xylene stream. After dissolving most of the specimen, a very thin layer of polyethylene which shows certain aspects of the original lamellar structure was obtained. Stereoscopic micrographs revealed the structure of polyethylene consisting of curved layers, concave, convex and other forms. These curved layers were identified by analysis of the Bragg fringes to be the crystalline lamellae. A special pattern resembling a spider in shape caused by a spherical crystal was investigated.
Low molecular weight by‐products in the Ziegler polymerization of higher terminal olefins
Authors: Aubrey D. W. , Barnatt A. 
Published: April 2003

AbstractFor the polymerization of n‐octadecene‐1 with catalysts derived from titanium tetrachloride and triethylaluminum, it has been shown that, in addition to polymerization of the olefin, the formation of isomerized olefin occurs. The latter is predominantly trans‐n‐octadecene‐2 and its formation is favored by increase in Al:Ti mole ratio, in catalyst concentration, and in reaction temperature. It has also been shown that 1,1‐disubstituted ethylene is present in the nonpolymeric reaction products. The influence of added trans‐n‐octadecene‐2 or trans‐n‐octadecene‐7 on the polymerization of n‐octadecene‐1 has been studied, and it is shown that the 2‐isomer has the more pronounced effect on polymer yield and intrinsic viscosity. It has also been shown that no significant copolymerization of terminal with nonterminal octenes or octadecenes occurs under these conditions. Results indicate that, in polymerizations of this kind, the interaction of catalyst with isomerized monomer is probably an important factor in determining polymer yield and molecular weight. The isomerization reaction is also of interest as a general preparative method for trans‐2‐olefins.
Some new polymeric semiconductors
Authors: Paushkin Ya. M. , Vishnyakova T. P. , Nisova S. A. , Lunin A. F. , Omarov O. Yu , Markov Yu. Ya , Machus F. F. , Golubeva I. A. , Polak L. S. , Patalakh I. I. , Stychenko V. A. , Sokolinskaya T. A. 
Published: April 2003

AbstractThis paper deals with some new methods for synthesis of the polymeric semiconductors by conjugated reactions and also with electrophysical properties of the polymers. Elimination of hydrogen halides from α,β‐dihalo derivatives by bases (calcium oxide or tertiary amines) yields polymers with conjugated bonds. The reaction proceeds at 200–300°C. under atmospheric or elevated pressures, acetylenes being the intermediates. α,β‐Dihalo compounds with calcium carbide above 150°C. produce polyacetylenic copolymers by elimination of two moles of hydrogen halide, also by generating acetylene from calcium carbide. The identical reaction (elimination of water) was observed between carbonyl compounds and calcium carbide. Elimination of water from monoand bifunctional phenols in the presence of zinc chloride under pressure above 200°C. yields polyphenylenes and polyhydroxyphenylenes, dehydrobenzene (benzyne) and hydroxybenzyne being intermediates. The polyhydroxyphenylenes prepared have a degree of polymerization from 4–5 to several thousand and are of interest as intermediates for thermostable resins, inhibitors etc. Linear polycyanamide and polycyanic acid were first prepared by polycondensation of urea with ammonium bicarbonate in the presence of zinc chloride. Analogous polymers were obtained from the ring‐opening polymerization of melamine and cyanuric acid. The polymers show good semiconductor and ion‐exchange properties. Polycondensation of ketones with ammonium bicarbonate also gave conjugated polymers. Thus, organometallic polymers were prepared from acetyl‐ and diacetyl ferrocene. We have also studied electrophysical, magnetic, and catalytic properties of the conjugated polymers prepared by the new methods. The electrical conductivity of the best specimens ranged from 10−3 to 10−6 ohm−1 cm.−1; the number of electrons unpaired was 1018–1019 spins/g.
Studies in cyclocopolymerization. III. Copolymerization of divinyl ether with certain nitrogen‐containing alkenes
Authors: Butler George B. , Vanhaeren Gerard , Ramadier Marie Francoise 
Published: April 2003

AbstractThe copolymerization of divinyl ether with fumaronitrile (A), tetracyanoethylene (B), and 4‐vinylpyridine (C) has been studied, azobisisobutyronitrile being used as initiator. The compositions of the copolymers were calculated from their nitrogen and unsaturation content. Over a wide range of initial monomer composition, the mole fraction of A in the copolymers lies in the range 0.55–0.63, and the copolymers contained only 2–3% unsaturation, indicating a high degree of cyclization. The composition of the copolymers of B indicated that cyclization occurred to only a small extent, as the copolymers contained rather high unsaturation content. The values of r1 = 0.23 and r2 = 0.12 were obtained. The mole fraction of C in the copolymers lies between 0.85 and 0.998. If the assumption is made that r1 ⋍ rc ⋍ 0 and there is predominant cyclization, r2 = 32.0 in this case. The difference in the composition of the copolymers is attributed to the difference between the electron density of the double bonds in A, B, and C.
Synthesis of 1,4,5,6,7,7‐hexachloro‐ and hexabromobicyclo‐[2,2,1]‐5‐heptene‐2‐carboxylic acid vinyl esters and copolymerization with acrylonitrile
Authors: Kovacs J. , Marvel C. S. 
Published: April 2003

Abstract1,4,5,6,7,7‐Hexachloro‐ and hexabromobicyclo‐[2,2,1]‐5‐heptene‐2‐carboxylic acid vinyl esters have been prepared by esterification of the Diels‐Alder addition products of hexachloro‐ and hexabromocyclopentadiene with acrylic acid. These monomers have been copolymerized with acrylonitrile to yield flame‐retardant polymers. Copolymers having a chlorine content up to 18.35% or a bromine content up to 6.35% burn, but copolymers containing 25.0% or more of chlorine or 9.83% or more of bromine do not support combustion.
Grafting of polyacrylonitrile to granular corn starch
Authors: Brockway C. E. , Seaberg P. A. 
Published: April 2003

AbstractAcrylonitrile grafts readily to granular corn starch in aqueous slurry when initiated by hydrogen peroxide plus activator. Prime evidence for grafting lies in the ease of separating PAN from starch in high yield when the initiator is azobisisobutyronitrile rather than peroxide. Grafting efficiencies are determined by extraction with appropriate solvents: dimethylformamide for homo‐PAN, and boiling water for ungrafted starch. Grafting efficiencies of PAN range from 78 to 95%, M̄n values for grafted PAN are 4,000 to 90,000, and frequency of attachment of side chains range from 300 to 1100 glucose units per chain. Increasing the monomer level, at fixed initiator concentration, tends to result in longer rather than more frequent side chains. AN behaves much as has been previously found for MMA, but the somewhat more efficient grafting at more frequent intervals and the more nearly uniform distribution of polymer in the starch granule suggest that AN penetrates the starch granule more readily than MMA.
Some considerations of the kinetics of the acid hydrolysis of poly‐ and oligosaccharides. Part III. The disaccharides 2‐O‐(α‐D‐glucopyranosyluronic acid)‐D‐xylose, 2‐O‐(4‐O‐methyl‐α‐D‐glucopyrano‐syluronic acid)‐D‐xylose, and 2‐O‐(4‐O‐methyl‐α‐D‐glucopyranosyl)‐D‐xylitol
Authors: Meller Alexander 
Published: April 2003

AbstractRate equations have been formulated for the formation and depletion of the hydrolysis product(s) of the title disaccharides. They are based on the assumptions that (1) the rate of acid hydrolysis of the disaccharides is according to first order, and (2) the rate of depletion of the hydrolysis product(s) is constant in the early periods while it approaches first order in the more advanced stages of the reactions. By using experimental rate data from the literature the rate constants of the hydrolysis of the disaccharides and of the depletion of the hydrolysis product(s) have been computed. The validity of the assumptions underlying the rate equations advanced has been confirmed by (a) the agreement between experimental and calculated values and (b) the similar values for the rate constant of the depletion of xylose formed in the hydrolysis of the two biouronic acids. Also discussed are some implications arising from the magnitude of the hydrolysis rate constant of methylaldobiouronic acid and of the depletion rate constant of xylose in relation to complete hydrolysis of polysaccharides.
α,ω‐Glycols from copolymers of isobutylene and 2,5‐dimethyl‐2,4‐hexadiene
Authors: Hecht J. K. , Marvel C. S. , Campbell T. W. 
Published: April 2003

AbstractIsobutylene has been copolymerized with 2,5‐dimethyl‐2,4‐hexadiene using a boron trifluoride catalyst in petroleum ether solution. Ozonization of the products followed by reduction with lithium aluminum hydride has furnished polyisobutylene glycols in good yield.
Cyclocopolymerization of bicyclopentene and other dicyclic dienes with sulfur dioxide to fused ring systems
Authors: Meyersen Klaus , Wang Jean Y. C. 
Published: April 2003

AbstractThe synthesis and cyclocopolymerization with sulfur dioxide of four 1,5‐ and 1,6‐dienes (bicyclopentene, bicyclohexene, dicyclopentenyl ether, and dicyclohexenyl ether) and one tetraene (quartercyclopentene) is described. Under optimum conditions, completely soluble copolymers are obtained from bicyclopentene in high conversions at temperatures down to −39°C. Bicyclohexene also gave soluble copolymers, but in a by far slower reaction and in low conversion. Quartercyclopentene does copolymerize, but as expected, gives only insoluble polymers. The two compounds with 1,6‐diallyl ether structure, dicyclopentenyl ether and dicyclohexenyl ether, failed to polymerize. The influence of initiator, temperature, reaction medium, diene concentration, etc., on the properties of the polymers was studied in detail for copolymerizations of bicyclopentene. Only a very limited number of peroxides in unusual large quantities was found to be effective in initiating this copolymerization. The reaction is further limited to a narrow choice of solvents, e.g,. diethyl ether and tetrahydrofuran, in order to obtain soluble products. Polymerization could not be achieved in ethanol, benzene, methylene chloride, dimethyl sulfoxide, and tetramethylene sulfone; excess sulfur dioxide yields only dark and insoluble products. Diene concentrations of below 0.3 wt.‐% are normally required to obtain poly(bicyclopentene sulfones) which are soluble in dimethyl sulfoxide, tetramethylene sulfone, or sulfuric acid. Polymerization can be carried out from room temperatures down to −39°C.; optimum results are generally obtained around 0°C. Inherent viscosities of 1.72 (0.5 g./100 ml. dimethyl sulfoxide) have been measured. X‐ray diffractions are those of amorphous polymers.
Kinetics of the solution polymerization of dioxolane in the presence of water
Authors: Kučra Miloslav , Hladký Eduard , Majerová Karla 
Published: April 2003

AbstractWater acts as a cocatalyst in the polymerization of dioxolane initiated by the ion pair ∼Si⊕HSO4⊖. The dependence of the reaction rate on the water concentration exhibits a maximum, the width of which strongly depends on the concentration of dioxolane. The change of the coordinates of the maximum and its shape with the decrease of the monomer concentration causes the reaction rate to decrease with increasing conversion. The point at which the slope of the conversion curve changes is a function of initial concentration of water. There is a very fast decrease of the concentration of free water in the polymerizing system. The consumption of water is associated with some peculiarities. The amount of free water which remains in the system is a function of the concentration of the original initiator. The ratio [H2O]∞/[initiator] is constant over a rather broad range of initial concentration of water.
Radiation‐induced solid‐state polymerization in binary systems. IV. Solid‐state polymerization in the glassy phase
Authors: Kaetsu Isao , Tsuji Kozo , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

AbstractThe radiation‐induced polymerization of glass‐forming systems containing monomers has been investigated. It was found that irradiation below the second‐order transition temperature Tg of the systems causes no in‐source polymerization but causes a rapid postpolymerization on warming above the Tg after initial irradiation below the Tg. The post‐polymerization was followed by differential thermal analysis and ESR spectra. It is caused above the Tg by the release of peroxy radicals trapped below the Tg, and its rate is proportional to the irradiation dose to some extent, often is explosively high, and brings about a remarkably large temperature rise by accumulation of polymerization heat. Irradiation above the Tg causes rapid in‐source polymerization which is accelerated by the high viscosity of the monomeric system between Tg and Ts (WLF temperature) compared to crystal or ordinary solution polymerization. The temperature dependence of the in‐source polymerization of glassy systems shows a peak between the Tg and Ts which may be the result of competing effects of the rate increase by the decreased termination near Ts and the rate decrease by the decreased propagation caused by the diffusion prevented near the Tg. The degree of polymerization was also investigated. The temperature dependence of the degree of polymerization of the polymers obtained by in‐source polymerization shows a peak similar to that of the temperature dependence of conversion. Unusually large values of the Huggins constant k' are noted between Tg and Ts. The degree of polymerization of the polymer obtained by post‐polymerized increases with the increase of irradiation dose and the polymerization rate; this may be the result of decreased chain transfer to nonpolymerizable components.
Effect of reaction medium on copolymerization of acrylonitrile and methyl acrylate
Authors: Izumi Zenzi , Kitagawa Hideji 
Published: April 2003

AbstractThe copolymerization of acrylonitrile (AN) with methyl acrylate (MEA) has been investigated in three types of polymerization, i.e., emulsion polymerization in water with a water‐soluble initiator, suspension polymerization in water with an oil‐soluble and water‐insoluble initiator, and solution polymerization in dimethyl sulfoxide (DMSO). Monomer reactivity ratios at 50°C. for AN and MEA are found to be r1 = 0.78 ± 0.02, r2 = 1.04 ± 0.02 in emulsion polymerization; r1 = 1.02 ± 0.02, r2 = 0.70 ± 0.02 in DMSO solution polymerization; r1 = 0.75 ± 0.05, r2 = 1.54 ± 0.05 in suspension polymerization. The large differences found in the reactivity ratios may be attributed to the different ratio of concentration of two monomers in the loci of polymerization. Chemically, AN is somewhat more reactive than MEA as shown by the reactivity ratios in DMSO. In the case of the suspension polymerization, the MEA/AN ratio in the polymer particles in which polymerization occurs may be higher than that in the total phase. Experimental results of the emulsion polymerization show that the emulsion polymerization of AN occurs both in the particles and in water. In addition, rates of the copolymerization of AN with MEA have also been investigated.
Reactivity of ester groups on insoluble polymer supports
Authors: Letsinger R. L. , Jerina D. M. 
Published: April 2003

AbstractA study was made of the comparative rates of reaction of active ester functional groups (p‐nitrophenyl and 2,4‐dinitrophenyl esters) situated on three types of insoluble support polymers and on small, soluble analogs of the polymer molecules. The supports consisted of a styrene—divinylbenzene bead‐type polymer (2% DVB), a styrene—divinylbenzene popcorn polymer (0.2% DVB), and a popcorn polymer with 2,3‐dimethylbutadiene and substituted styrene units in the chain. p‐Nitrophenyl benzoate and 2,4‐dinitrophenyl p‐isopropylbenzoate were used as soluble analogs. Rates of aminolysis by small molecules (2‐aminoethanol and n‐tetradecylamine) in pyridine and of solvolysis in alcohols catalyzed by both small (N‐methylimidazole) and large (polyvinylimidazole) molecules were determined. With the small amines, finely divided particles of popcorn and bead type styrene polymers reacted at about the same rate, which was approximately 1/5 the rate of reaction of the homogeneous analogs. With a high molecular weight reagent, polyvinylimidazole, the heterogeneous reactions were much slower and the popcorn polymer reacted faster than the bead polymer. In catalyzed solvolyses, the styrene popcorn derivative reacted faster in benzyl alcohol and slower in 1‐hexanol than the dimethylbutadiene popcorn polymer derivatives.
Determination of tacticity in poly(vinyl chloride) by infrared spectroscopy
Authors: Štokr J. , Schneider B. , Kolínský M. , Ryska M. , Lím D. 
Published: April 2003

AbstractFrom the temperature dependence of infrared spectra of poly(vinyl chloride) samples prepared by different methods, the intensity of the band at 690 cm.1 (proportional to the number of isotactic diads in the sample), as well as that of the tacticity‐independent CH stretching band, was found to be independent of the crystallinity of the sample. These lines were therefore applied for the tacticity determination in poly(vinyl chloride), measured in the form of KBr pellets. The numerical tacticity value was obtained from the known values of absorbance coefficients of SCH and SHH type CCl stretching bands in solution, and from the shape of the spectrum.