bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymérisation “basse pression” de l'ethylène en préasence de noir de carbone
Authors: Donnet J. B. , Wetzel J. P. , Riess G. 
Published: April 2003

AbstractThe polymerization of ethylene with Ziegler‐Natta catalysts in the presence of carbon black has shown three characteristic features both with a heterogeneous catalyst, AlBu3TiCl4, and with a soluble catalyst, Cl2Ti(C5H5)2AlEt2Cl. They are, in order of increasing importance: reactivity of the organoaluminum derivatives with surface chemical groups of the carbon black, adsorption of a certain amount of organoaluminum compounds on the carbon black surface, and influence of the specific surface of carbon black, which controls the dispersion degree of the catalytic system. Furthermore, it was possible to obtain polyethylene by this procedure, containing different amounts and different types of carbon black.
Polymerization of cyclobutene rings. VI. Influence of the organometallic compound of the Ziegler‐Natta catalysts on the mechanism of polymerization of cyclobutene and 3‐methylcyclobutene
Authors: Dall'Asta G. 
Published: April 2003

AbstractThe polymerization of cyclobutene and 3‐methylcyclobutene in the presence of Ziegler‐Natta catalysts was studied especially in view of the influence of the metal alkyls on the course of polymerization. Several metal alkyls of the main groups I–IV of the periodic table of elements were investigated, vanadium halides being used as transition metal compounds. The influence of the metal alkyl was found not to be limited to the activity of the catalyst system, which is maximum for aluminum alkyl, but also to extend to the polymerization mechanism. Depending on the metal alkyl, the two cyclobutene monomers can in fact be polymerized by two different mechanisms, i.e., by opening of the double bond or by ring opening with retention of the double bond. No migration of the double bond is involved in these polymerizations. An interpretation of the different experimental observations is tentatively proposed, and the relationship with the stereospecific polymerization of the α‐olefins is stressed.
Polymerization of cyclobutene rings. VII. Polymerization of bicyclo[4,2,0]octa‐7‐ene and bicyclo[3,2,0]hepta‐2,6‐diene with Ziegler‐Natta catalysts and with group VIII metal halides
Authors: Dall'Asta G. , Motroni G. 
Published: April 2003

AbstractThe polymerization of bicyclic olefins containing a cyclobutene and a higher‐membered ring was studied by using Ziegler‐Natta systems as well as group VIII metal halides as catalysts. Only the cyclobutene moiety of the monomers proved reactive in polymerization, whereas the higher‐membered ring moieties enter unchanged in the polymer chains as side groups. In spite of the considerable bulkiness of the monomers, homopolymerization by opening of the double bond as well as by ring opening take place readily. Steric isomerism of the monomer units and the problem of the site of opening of the cyclobutene ring are discussed.
Cationic polymerization of α,β‐disubstituted olefins. IV. Stereospecific polymerization of propenyl alkyl ethers catalyzed by BF3·O(C2H5)2 and Al2(SO4)3–H2SO4 complex
Authors: Higashimura T. , Kusudo S. , Ohsumi Y. , Mizote A. , Okamura S. 
Published: April 2003

AbstractThe cis‐ and trans‐propenyl alkyl ethers were polymerized by a homogeneous catalyst [BF3·O(C2H5)2] and a heterogeneous catalyst [Al2(SO4)3–H2SO4 complex]. Methyl, ethyl, isopropyl, n‐butyl and tert‐butyl propenyl ethers were used as monomers. The steric structure of the polymers formed depended on the geometric structures of monomer and the polymerization conditions. In polymerizations with BF3·O(C2H5)2 at −78°C., trans isomers produced crystalline polymers, but cis isomers formed amorphous ones except for tert‐butyl propenyl ether. On the other hand, highly crystalline polymers were formed from cis isomers, but not from the trans isomers in the polymerization by Al2(SO4)3–H2SO4 complex at 0°C. The x‐ray diffraction patterns of the crystalline polymers obtained from the trans isomers were different from those produced from the cis isomers, except for poly(methyl propenyl ether). The reaction mechanism was discussed briefly on these basis of these results.
Cationic polymerization of α,β‐disubstituted olefins. V. Reactivity of propenyl alkyl ethers in cationic polymerization
Authors: Higashimura T. , Kusudo S. , Ohsumi Y. , Okamura S. 
Published: April 2003

AbstractTo elucidate the effect of the introduction of a methyl group in the β‐position of a vinyl monomer, propenyl alkyl ethers were copolymerized with vinyl ethers having the same alkoxy group. Propenyl alkyl ethers with an unbranched alkoxy group (ethyl or n‐butyl propenyl ether) were more reactive than the corresponding vinyl ethers. This behavior is quite different from that of β‐methylstyrene derivatives. However, propenyl alkyl ethers with branched alkoxy groups at the α carbon atom (isopropyl or tert‐butyl propenyl ether) were less reactive than the corresponding vinyl ethers. Also, cis‐ isomers were more reactive than the trans isomers, regardless of the kind of alkoxy group and the polarity of the solvent.
Base‐catalyzed hydroxymethylation of phenol by aqueous formaldehyde. Kinetics and mechanism
Authors: Zavitsas Andreas A. , Beaulieu Raymond D. , Leblanc John R. 
Published: April 2003

AbstractThe effects of formaldehyde and hemiformal equilibria on the rates of the base‐catalyzed and hydroxymethylations of phenol by aqueous formaldehyde have been treated quantitatively. A kinetic model treating all seven simultaneous, parallel, consecutive, and competing reactions, as well as the equilibria, has been shown to apply to a wide variety of the conditions and to data from other works. Concentration‐induced solvent effects on the rates and on the ortho/para‐substitution patters have been studied. The temperature dependence of the rate constants, both for dilute systems and systems composed primarily of phenol and aqueous formaldehyde, has been determined.
Polymerization of 2,2,2‐trifluoroethyl vinyl ether
Authors: Chiklis C. K. , Haas H. C. 
Published: April 2003

AbstractThe polymerization of 2,2,2‐trifluoroethyl vinyl ether by six different catalyst systems was examined. Low‐temperature studies (−78°C) with boron trifluoride etherate catalyst in hydrocarbon and chlorinated solvents slowly yielded low molecular weight polymers which were amorphous and noncrystallizable upon cold drawing. Under similar conditions, polymerizations with boron trifluoride gas were spontaneous, quantitative, and gave relatively high molecular weight, form‐stable, amorphous polymer. Heterogeneous polymerizations with chromium trioxide crystals in toluene at 68°C and bulk reactions with ethylmagnesium bromide–carbon tetrachloride catalyst at 40°C failed to produce polymer. Room temperature runs with triisobutylaluminum–titanium tetrachloride catalyst gave amorphous, tacky material. Aluminum hexahydrosulfate heptahydrate (AHS) initiated polymerizations conducted at 25 and 60°C gave low yields of mixtures of amorphous and crystalline polymers, the ratio depending upon the polymerization solvent employed. The infrared spectra and x‐ray diffraction intensity curves of crystalline and amorphous poly(trifluoroethyl vinyl ether) are reported and compared herein for the first time.
1,5‐Polymerization of 1‐thioacylaziridines
Authors: Iwakura Yoshio , Nabeya Aiko , Nishiguchi Takeshi 
Published: April 2003

AbstractFour thioacylaziridines, 1‐thioaroyl‐, 1‐(N‐phenylthiocarbamyl)‐, 1‐(aryloxythiocarbonyl)‐, and 1‐(aryldithiooxycarbonyl)aziridines, were found to undergo 1,5‐polymerization to giving polymers of polyiminothioether, polyisothiourea, polyiminothiocarbonate, and polyiminodithiocarbonate structure, respectively. The 1,5 polymerization may be explained by the kinetic factors rather than the thermodynamic ones.
Cupric sulfate–hydrazine system as an initiator of vinyl polymerization. II. Polymerization of methyl methacrylate in aqueous solution in the absence of oxygen
Authors: Bond Joan , Lee P. I. 
Published: April 2003

AbstractThe cupric sulfate–hydrazine system has been used to initiate the aqueous solution polymerization of methyl methacrylate at pH 9.25 in the absence of oxygen. There is no decomposition of hydrazine on the surface of the reduced cupric hydroxide until a flocculant precipitate is formed (cupric sulfate concentration of about 10−3 mole/1). Below this concentration, the initiating reaction occurs solely in solution, the rate of polymerization decreasing when the reaction mixture becomes depleted in cupric ions. When a suitable surface area of the precipitated polymer is attained, adsorption and decomposition of hydrazine occurs on its surface, causing further initiation of polymerization.
Polymerization studies on allylic compounds. III. α(substituted methyl)styrenes
Authors: Baldwin M. G. , Reed Samuel F. 
Published: April 2003

AbstractThe free‐radical polymerization of a series of α‐(substituted methyl)styrenes was investigated. These compounds were found to be inactive in homopolymerizations but copolymerized with methyl methacrylate and styrene with a retarding effect. Copolymerization characteristics were followed by rate and viscosity measurements.
Syndiotactic and isotactic poly(tert‐butylethylene oxide)
Authors: Price Charles C. , Fukutani H. 
Published: April 2003

AbstractThe rate of polymerization of t‐BuEO by t‐BuOK in DMSO is about one‐tenth that of propylene oxide. The slow rate of propagation was accompanied by considerable chain transfer. In the absence of solvent, the polymer obtained was crystalline, different from the isotactic form and therefore must be syndiotactic. The NMR spectra indicate the isotactic polymer exists in solution preferentially in the skew1 form, while syndiotactic is about 60% skew1, 40% skew2. Amorphous polymer accompanying isotactic exists about 50% in the trans conformer, by NMR data.
Calorimetric investigation of polymerization reactions. I. Diffusion‐controlled polymerization of methyl methacrylate and styrene
Authors: Horie Kazuyuki , Mita Itaru , Kambe Hirotaro 
Published: April 2003

AbstractThe rate of bulk polymerization of methyl methacrylate and styrene was determined directly, continuously and over the whole range of conversion with a differential scanning calorimeter (DSC) operated isothermally. At the later stages of the accelerated polymerization of methyl methacrylate, a previously unknown inflection or peak in the rate of polymerization was observed. The variation of the rate after the onset of the gel effect, including this peculiar inflection, was interpreted on the basis of the diffusion behavior of monomer molecules and polymeric radicals in the polymer–monomer system, their diffusion rates being predicted from the free volume theory. The final conversion at which no further polymerization proceeds was determined for both monomers. It was affirmed quantitatively that the final conversion has a close relation with the transition of the polymer–monomer system from a viscous liquid to a glassy state.
Synthesis and investigation of properties of repeatedly grafted copolymers (pemosors)
Authors: Korshak V. V. , Mozgova K. K. , Egorova Yu. V. 
Published: April 2003

AbstractRepeatedly grafted copolymers (pemosors) were obtained by grafting one and the same or different vinyl monomers onto heterochain polymers in a radical reaction. As starting polymers films of polyethylene terephthalate and poly‐ε‐caproamide were used. Styrene and methyl methacrylate were the grafted vinyl monomers. It has been shown that pemosors could be formed in yields of 500–1000% (of the starting sample weight) by multiple grafting on vinyl polymer. Pemosors differ in appearance both from the starting polymers and the single‐graft copolymers. Investigations of pemosor samples by electron microscope showed that the morphological structure of the surface was appreciably affected, the changes being more significant with increasing content of the grafted polymer. X‐Ray studies and NMR data on pemosors showed that multiple grafting of vinyl monomers does not change the crystal structure of the starting polymers, affecting only the supermolecular structure of the outer layer. Pemosors are polymers of a new type, differing in their properties from the starting polymers and the single‐graft copolymers. The grafting character and penetration depth of the grafted monomer depend on the packing compactness of the supermolecular structure of the polymeric base as well as on the chemical nature of the starting polymers and monomers. Pemosors possess considerable chemical resistance and withstand prolonged boiling in 40% alkali solution.
Hydrazine‐based polyimides and model compounds
Authors: Dine‐Hart R. A. 
Published: April 2003

AbstractThe reaction of hydrazine hydrate with aromatic anhydrides may give either N‐amino imides or cyclohydrazides. The conditions that favor the formation of N‐aminoimides, in which the imide contains respectively a 5‐ and 6‐membered ring, are discussed. These compounds may be reacted with aromatic anhydrides to give N‐N‐linked imides. The properties of a number of model compounds and polymers are described, and it is shown that those compounds which have alternating 5‐ and 6‐membered imide rings give the maximum oxidative stability in air at 400°C.
Investigation of the change in the fine structure of Valonia cellulose upon wet heating and mercerization
Authors: Okajima Saburo , Kai Akira 
Published: April 2003

AbstractA Valonia cellulose (NV), a cellulose II derived from NV by mercerization (MV), and a cast cellulose II film (F) were deuterated repeatedly (wetting‐drying cycle) in vapor phase at 25°C; the integrated deuteration time amounts to 5 × 105 min. A region C, which cannot be attacked by the exchange reaction, exists in NV and MV, amounting to 80 and 18% in the respective samples. In the case of F, it could not be determined exactly due to the too large scattering of the data. On heating in liquid D2O for 5 or 10 min., OD groups develop within C above 190 and 170°C in NV and MV, respectively. Above 190°C. the exchange is larger in NV than in MV. These OD groups within the pre‐existing crystallites begin to disappear after treating with NaOH solution at the concentration at which cellulose begins to be converted to alkali cellulose I. The resistant OD groups developed within the amorphous and intermediate regions are rehydrogenated by the more dilute alkaline solutions.
Thermal degradation of nadic methyl anhydride‐crosslinked novolac epoxy resin
Authors: Freeman Eli S. , Becker Aaron J. 
Published: April 2003

AbstractThe physicochemical high‐temperature reactions of a nadic methyl anhydride‐cross‐linked novolac epoxy resin were investigated by means of differential thermal analysis, thermogravimetric analysis, and by other analytical procedures. The thermogravimetric study revealed that decomposition involving weight loss occurred in two stages. Chemical analysis showed that the major gaseous products formed during weight loss were 2‐methylcyclopentadiene, carbon dioxide, and carbon monoxide. The formation of a fine mist of solid particles was observed during the second stage of degradation. Changing various experimental parameters affected the degradation processes. The kinetics of degradation were also investigated. The method of Freeman and Carroll was used to find that a zero‐order rate law was followed at the beginning of both first and second stages of reaction. The activation energy associated with the major portion of the first stage of weight loss was 15 kcal/mole. There was good agreement between the observed reaction rates and the reaction rates calculated from a theoretical model which depended on desorption as the rate‐controlling step. The activation energy for the beginning of the second stage of weight loss was 24 kcal/mole. By using DTA, the heat of exothermal reaction during this latter phase of decomposition was evaluated as 65 cal/g.
Emulsion polymerization. VI. Concentration of monomers in latex particles
Authors: Gardon J. L. 
Published: April 2003

AbstractNonpolymerizing latex particles surrounded by an aqueous phase saturated with monomer absorb only a finite amount of monomer, even if the monomer is a good solvent for the polymer, because the surface energy of each particle increases on swelling. At equilibrium the change in surface energy and the free energy of mixing exactly balance. Equations based on this thermodynamic principle predict with good accuracy the saturation swelling of crosslinked and uncrosslinked latex particles and the partitioning of monomer between the aqueous phase and latex particles at partial saturation. The available experimental data on swelling of latex polymers with monomers are reviewed. Earlier papers assumed that during emulsion polymerization the monomer concentration in the latex particles is independent of conversion as long as monomer droplets are present. This assumption is shown to be a justifiable approximation. The thermodynamics of the swelling of latex particles with a blend of two monomers is presented. The calculations indicate that copolymerization in emulsion should define reactivity ratios differing from those of homogeneous copolymerization by not more than 40% if the solubility of the comonomers in water is low. The reactivity ratio scheme is strictly applicable to emulsion copolymerization if the solvent properties of the two comonomers are identical.
Study on modification of polymers with the aid of the Schmidt reaction
Authors: Ravve A. 
Published: April 2003

AbstractA study of the Schmidt reaction on several polymers with pendant carboxylic and ketone moieties was carried out. Four polymers were used as starting materials: (1) poly(methyl vinyl ketone), (2) poly(acrylic acid), (3) a copolymer of methyl vinyl ketone and acrylic acid, and (4) a copolymer of styrene and acrylic acid. Most reactions were conducted in an acetic acid medium with the exception of one reaction on poly(acrylic acid) which was done in dioxane and another on copolymer of styrene and acrylic acid done in chloroform. It was found that a Schmidt reaction on poly(acrylic acid) in acetic acid solution will lead to intermolecular reactions of the intermediate with the solvent in preference to reactions with neighboring carboxyl groups on the polymer backbone. A tendency of poly(acrylic acid) to form cyclic anhydrides under these reaction conditions interferes with the yield of acetamide units.
Aminobutadienes. X. Polymerization and copolymerization of 2‐phthalimidomethyl‐1,3‐butadiene
Authors: Murata Kenichi , Terada Akira 
Published: April 2003

AbstractThe polymerization and copolymerization of 2‐phthalimidomethyl‐1,3‐butadiene were investigated. This monomer was easily polymerized by benzoyl peroxide catalyst in bulk or in solvent, and by γ‐radiation in the solid state to give polymers having a softening point of 135–145°C. Although these resulting polymers did not give x‐ray diffraction patterns, they showed crystalline patterns by electron diffraction. On the other hand, cationic polymerization with the use of boron trifluoride diethyl etherate in chloroform was attempted, but no formation of the polymer was observed. Also, this monomer was easily copolymerized with styrene in N,N‐dimethylformamide. The monomer reactivity ratios and Alfrey‐Price Q and e values calculated from the copolymerization data of this monomer (M1) with styrene (M2) were r1 = 2.0 ± 0.13, r2 = 0.15 ± 0.02, and Q1 = 2.78, e1 = 0.30.
Soluble high polymers from allyl methacrylate
Authors: Higgins J. P. J. , Weale K. E. 
Published: April 2003

AbstractAllyl methacrylate has been polymerized by free‐radical methods and found to yield a soluble polymer in carbon tetrachloride, dioxane, and diallyl ether solutions. The overall rate equation in diallyl ether is Rp = k[ln]0.7[M]1.6. It is suggested that propagation and cyclization reactions proceed only via addition to the methacrylyl groups of the monomer. Some degradative chain transfer occurs with the allyl groups, and it is considered that the solvents may ensure the production of soluble polymers by reactions in which allyl–radical side chains are terminated without crosslinking.
1,2‐Dinitrile polymers. I. Hompolymers and copolymers of fumaronitrile, maleonitrile, and succinonitrile
Authors: Liepins R. , Campbell D. , Walker C. 
Published: April 2003

AbstractHomopolymers and copolymers of fumaronitrile, maleonitrile, and succinonitrile have been prepared by using medium high temperature free‐radical initiators. Black, nonfusible but soluble polymers were obtained. The spectroscopic and chemical evidence indicated a structure containing α‐pyrrolenine rings and no free nitrile groups in the fumaronitrile and maleonitrile polymers and 1‐pyrroline rings and free nitrile groups in the succinonitrile polymers. The polymers possessed good thermal stability, free spin concentration of 1017–1018 spins/g, and an ac conductivity at room temperature in nitrogen of 10−6 to 10−8 ohm−1 cm−1.
Metal‐containing initiator systems. IV. Polymerization of methyl methacrylate by systems of some activated metals and organic halides
Authors: Otsu Takayuki , Yamaguchi Masami 
Published: April 2003

AbstractA study of the polymerization of methyl methacrylate initiated by the binary systems of some activated metals and organic halides has been made. It was found that the initiator activities of these systems were greatly dependent on the kind and the preparation or activation method of the metals (i.e., oxidation potential, surface area, and purity), and also on the kind of organic halides (i.e., bond‐dissociation energy of their carbon–halogen bonds). From the kinetic studies of the polymerization at 60°C with the system reduced nickel–carbon tetrachloride, the rate of polymerization was found to be proportional to the monomer concentration and to the square root of concentration of both nickel and carbon tetrachloride at the lower concentration range of carbon tetrachloride, indicating that the system induced the radical polymerization. A similar conclusion was also obtained from the copolymerization with styrene with this system at 60°C, i.e., the resulting copolymer composition curve was in agreement with that obtained with azobisisobutyronitrile (AIBN). The apparent overall activation energy for the methyl methacrylate polymerization with this system was estimated to be 7.5 kcal/mole, which was considerably lower than that with AIBN. On the basis of the results obtained, an initiation mechanism for the polymerization with these initiator systems is presented and discussed.
Olefin polymerizations and copolymerizations with aluminum alkyl–cocatalyst systems. I. Cocatalysis with brönsted acid systems
Authors: Kennedy J. P. 
Published: April 2003

AbstractCertain aluminum alkyls and aluminum dialkyl halides in conjunction with suitable simple cocatalysts generating proton or carbonium ion exhibit high polymerization activity and produce high molecular weight polyolefins, diolefins and/or copolymers at comparatively high temperatures. In this paper we report our investigations with AlEt2Cl–Brönsted acid systems used for polymerizing isobutylene and copolymerizing isobutene‐isoprene mixtures for high molecular weight products. The cocatalyst is not specific in these reactions. Highly active systems can be obtained with HCl, HBr, CCl3COOH, etc. Evidently proton donors in general (Brönsted acids) may function as cocatalysts in this system. The sequence of polymerization initiation activity of various Brönsted acids in conjunction with AlEt2Cl is HCl, HBr ≫ HF, H2O > CCl3COOH ≫ CH3OH > CH3COCH3. The effect of temperature on the molecular weights was studied. In contrast to linear plots of log molecular weight versus 1/T, obtained for polyisobutylene or isobutylene‐isoprene copolymers with conventional Friedel‐Crafts halides in the −30 to −100°C range, this Arrhenius plot showed a marked maximum near −70°C for polymers prepared with AlEt2Cl–HCl catalyst systems. Features of this polymerization reaction are discussed.