bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lithiation of diene polymers
Authors: Minoura Yuji , Shiina Kyo , Harada Hiroshi 
Published: April 2003

AbstractIt was found that the metallation of diene polymers with n‐butyllithium in n‐heptane takes place in the presence of a tert amine, i.e. N,N,N′,N′‐tetramethylethylenediamine. Butyllithium was added to the diene polymer in n‐heptane in the presence of an equimolar amount of the amine, and the mixture was allowed to react at 80°C. for 60 min. under nitrogen. As a result, 27% and 9% per monomer unit for polybutadiene and polyisoprene, respectively, were metallated. The effects of the concentrations of the diene polymer, butyllithium, and the amine on the reaction were studied at 80°C., and the reaction mechanism was discussed. The overall rate of metalation was proportional to the diene polymer concentration and to the square root of the butyllithium concentration. The overall activation energies of metalation were 6.6 and 8.4 kcal./mole for polybutadiene and polyisoprene, respectively. Many kinds of polymer derivative were obtained by treating the metalated polymers with various reagents, such as carbon dioxide, Michler's ketone, trimethylchlorosilane, triphenylchlorosilane, benzaldehyde, and pyridine.
Photochemical crosslinking of polypropylene
Authors: Kujirai C. , Hashiya S. , Furuno H. , Terada N. 
Published: April 2003

AbstractA study was carried to determine experimentally the crosslinking of irradiated polypropylene by ultraviolet rays in vacuo. Three methods of detecting crosslinking were used: measuring the degree of swelling in decalin at room temperature, measuring the gel fraction in a tetrachloroethylene solution of the irradiated sample, and comparing the infrared spectra before and after irradiation. It was found that as the time of irradiation increases, the degree of swelling decreases, whereas the gel fraction in tetrachloroethylene solution increases. This shows that the crosslinking reaction proceeds with time. On the other hand, the infrared spectra of the irradiated sample remained almost unchanged, which shows that different bond species can hardly be formed by irradiation in vacuo. From these facts it may be concluded that the measurements amply confirm the hypothesis. Furthermore, it is demonstrated that ash residue in polypropylene plays an important role in photocrosslinking; that is, the photochemical primary process of the reaction is the absorption of light by the ash residue.
Direct determination of crosslinking and chain scission in polymers
Authors: Kells D. I. C. , Koike M. , Guillet J. E. 
Published: April 2003

AbstractA direct method has been developed for determining G(crosslinks) for irradiated polymers using the analytical ultracentrifuge. The sedimentation velocity technique is employed to follow changes in the molecular weight of a narrow distribution polystyrene sample irradiated in vacuum with 60Co γ‐rays. It is shown that G(crosslinks) can be determined at low doses before significant structural changes have occurred in the polymer. At about one‐fifth of the gel dose G(crosslinks) was found to be 0.019 compared to a value of 0.040 obtained from gel‐sol fraction measurements. It is concluded that G(crosslinks) may increase with dose due to processes such as the addition of radicals to double bonds formed during the irradiation.
Liquid carbon dioxide as a solvent for the radiation polymerization of ethylene
Authors: Hagiwara Miyuki , Mitsui Hiroshi , Machi Sueo , Kagiya Tsutomu 
Published: April 2003

AbstractThe usefulness of liquid carbon dioxide as a solvent for polymerization of ethylene was studied. The effect of liquid carbon dioxide on the polymerization was investigated under conditions of the pressure of 400 kg./cm.2 over the temperature range 20–45°C. by using γ‐radiation and AIBN as initiators. The infrared spectrum of the polymers showed that carbon dioxide had little effect on the polymer structure. The polymers contained no combined carbon dioxide and only small amounts of vinylidene unsaturation. The methyl content of the polymers was 0.5–4.0 CH3/1000C. The polymer yield and molecular weight were found to be decreased by the addition of carbon dioxide in both polymerization by γ‐radiation and AIBN. The number of polymer molecules formed per unit time increased with the content of carbon dioxide in the γ‐ray polymerization, and was constant in the case of AIBN. The advantages of the use of liquid carbon dioxide as a solvent in this polymerization were also considered from the viewpoints of the continuous process, the separation of polymer, the stability of carbon dioxide to radiation, and commercial applications.
Kinetics of the γ‐radiation‐induced polymerization of ethylene in liquid carbon dioxide
Authors: Hagiwara Miyuki , Mitsui Hiroshi , Machi Sueo , Kagiya Tsutomu 
Published: April 2003

AbstractThe γ‐radiation‐induced polymerization of ethylene with the use of liquid carbon dioxide as a solvent, was studied from the viewpoint of kinetics. The polymerization was carried out at conversions less than 10% under the pressure ranging from 100 to 400 kg./cm.2, dose rates 1.3 × 104−1.6 × 105 rad/hr., and temperatures of 20–90°C. The concentration of carbon dioxide varied up to 84.1 mole‐%. The polymerization rate and the polymer molecular weight were observed to increase with reaction time. This observation, however, becomes less pronounced with increasing concentration of carbon dioxide and with rising temperature. The exponents of the pressure and the dose rate were determined to be 2.3 and 0.85 for the rate, and 2.0 and −0.20 for the molecular weight, respectively. From the kinetic considerations for these results, the effect of carbon dioxide on the initiation and termination reaction in the polymerization was evaluated.
Emulsion polymerization. II. Review of experimental data in the context of the revised Smith‐Ewart theory
Authors: Gardon J. L. 
Published: April 2003

AbstractTables are presented for convenient calculation of the basic parameters of the revised Smith‐Ewart theory. For the methyl methacrylate (MMA)/sodium lauryl sulfate (SLS)/K2S2O8, and for the styrene/SLS/K2S2O8 reaction mixtures parameters are presented from which the absolute values of the following quantities can be conveniently calculated for any temperature, soap, and initiator concentration: particle number, particle radius, conversion where particle nucleation stops, rate and molecular weight in interval II, the interval after completion of particle nucleation and before the disappearance of monomer droplets. The theoretical predictions are compared to new experimental data and to those from the literature. The available data confirm the theoretical prediction that particle nucleation stops after a very small amount of polymer is formed, of the order of 0.01 cc. polymer/cc. water in most recipes. The theory and experiments are in good qualitative agreement for the conversion rate prior to completion of particle formation: the conversion rate rises with time and, when particle nucleation stops, it levels off. Excellent quantitative agreement can be obtained between theoretical and experimental particle size values. In the experiments of this laboratory the SLS concentration was varied 60‐fold, the K2S2O8 concentration was varied 140‐fold and the difference between theoretical and experimental poly(MMA) particle radii was always less than about 20%. Similar good agreement was obtained for polystyrene over the temperature range 30–90°C. Some polystyrene data from the literature with carboxylic soaps give just as good fit as the data with SLS of this laboratory. The predicted proportionality between particle number and the product of 0.6 power of soap concentration and of 0.4 power of initiator concentration was observed for several monomers. The theoretical predictions for the rate and molecular weight obtained in interval II are valid only for relatively low initiator and high soap recipes. For recipes for MMA and styrene the rate data are in good agreement with those calculated from the theory. The theory also correctly predicts the order of magnitude of the experimental molecular weights. For several monomers the rate and molecular weight vary with initiator and soap concentrations in a manner close to theoretical predictions.
Cationic polymerization of cyclic dienes. V. Polymerization of the methylcyclopentadiene
Authors: Kohjiya Shinzo , Imanishi Yukio , Okamura Seizo 
Published: April 2003

AbstractMethylcyclopentadiene (MCPD) has been polymerized with cationic catalysts in toluene solution at −78°C. to a white powdery polymer, whose intrinsic viscosity in benzene solution at 30°C. ranged from 0.1 to 0.5. The comparison of the rate of homopolymerization of MCPD with that of cyclopentadiene (CPD) and the copolymerization of MCPD and CPD indicated that MCPD is much more reactive than CPD. It was suggested that the high stability of cycloalkenyl cation is responsible for the high reactivity of cyclic dienes. Infrared and NMR spectroscopy on polymethylcyclopentadiene showed that almost all of the monomer units in polymethylcyclopentadiene produced under the present conditions have a trisubstituted double bond. The mechanism of the initiation reaction in the polymerization of cyclic dienes is also discussed.
Electron‐transfer polymers. XXX. Preparation of poly(1‐vinyl‐3,4,6‐trimethyl‐2,5‐benzoquinone)
Authors: Nakabayashi Nobuo , Wegner Gerhard , Cassidy Harold G. 
Published: April 2003

Abstract1‐Vinyl‐3,4,6‐trimethyl‐2‐methoxy‐5‐hydroxy‐benzene (I) was prepared in good yield by the Wittig reaction from the corresponding chloromethyl compound. It could be polymerized cationically to low molecular weight material. The polymer could be oxidized to poly(1‐vinyl‐3,4,6‐trimethyl‐2,5‐benzoquinone) (III) and could be reduced to the corresponding hydroquinone. Compound (I) was acetylated at the phenolic hydroxyl group and polymerized. The acetyl group was quantitatively reduced with lithium aluminum hydride, and the resulting polymer could be oxidized quantitatively to (III). Its molecular weight was a little higher than that prepared directly from (I).
Kinetics of the polymerization of tetrahydrofuran in the presence of water
Authors: Kučera M. , Hladký E. , Majerová K. 
Published: April 2003

AbstractThe polymerization of tetrahydrofuran was studied with regard to the presence of polar and nonpolar compounds, or well‐solvating and poorly solvating compounds, respectively. Tetrahydrofuran is highly nucleophilic, with a high solvation ability. It is capable of activating the native initiator itself and can be polymerized without any added cocatalyst. The addition of water to the tetrahydrofuran–initiator system decreases the polymerization rate. However, the dependence of the polymerization rate on the concentration of water in the dilute tetrahydrofuran runs through a maximum. The reaction rate is a function of the position of an equilibrium established during the solvation of initiator. All components of the system take part in the establishment of equilibrium.
Polymerization of styrene with VCl4–aluminum alkyls
Authors: Anand L. C. , Dixit S. S. , Kapur S. L. 
Published: April 2003

AbstractPolymerization of styrene has been carried out with VCl4–AlEt3 and VCl4–Al(i‐Bu)3 catalyst systems. These two systems have been found to behave in a similar manner but their behavior is different from those systems where VOCl3 has been used instead of VCl4. Reaction is first order with respect to monomer concentration for both the systems and first order with respect to catalyst in the case of VCl4–AlEt3. In the case of VCl4–Al(i‐Bu)3, the rate of polymerization is independent of catalyst concentration but intrinsic viscosities increase with increasing catalyst concentration. The average valence of vanadium in the catalyst complexes has been discussed in relation to nature of catalyst sites. Activation energy and effect of diethyl zinc support the anionic mechanism for the two systems.
Study of Ziegler‐Natta catalysts. Part I. Valence state and polymerization activity
Authors: Kollár L. , Simon A. , Osváth J. 
Published: April 2003

AbstractPolymerization at temperatures lower than the temperature of catalyst formation induces no changes in the solid phase of the catalyst formed by Al(C2H5)3 + TiCl4. In polymerizations with catalysts of this class, maximum activity is observed when the titanium component of the catalyst is trivalent. Any different behavior indicates the presence of aluminum alkyl chlorides in the liquid phase of the catalyst.
Solid‐state initiation of polymerization of N‐vinylcarbazole by gases
Authors: Meyers R. A. , Christman E. M. 
Published: April 2003

AbstractChlorine gas has been shown by previous investigators to initiate the polymerization of solid N‐vinylcarbazole at room temperature, giving a maximum yield of 66% polymer after 18 hr. This initiation of polymerization of N‐vinylcarbazole without the application of heat, by a gas, is the only solid‐state initiation other than those that are radiation‐induced known to us. This study was undertaken in order to determine both the scope and the mechanism of the room‐temperature solid‐state initiation of vinyl polymerization of N‐vinylcarbazole by gases. The gases (HCl, Cl2, and N2O4) were absorbed by solid N‐vinylcarbazole, giving very rapid exothermic polymerization: HCl, 37% polymer yield, M̄n 2500; Cl2, 50% polymer yield, M̄n 4703; N2O4, 91% polymer yield, M̄n 7073. The gases NOCl, BF3, and HBr were not absorbed by N‐vinylcarbazole and did not initiate polymerization. The N2O4‐initiated polymerization, which gave a high yield of polymer, was complete within 5 min. after introduction of gas. This polymerization method and the resulting polymer compared favorably with conventional peroxide‐initiated melt polymerization and the polymer obtained thereform. The mechanism of gas‐initiated polymerization, which was studied with introduction of inhibitors, appears to be classically cationic in nature.
Dehydrochlorination reactions in polymers. Part III. Vinylidene chloride–styrene copolymers
Authors: Haldon R. A. , Hay J. N. 
Published: April 2003

AbstractA systematic study of the effect of styrene units on the thermal stability of vinylidene chloride copolymers was made. In general, the copolymers were more easily dehydrochlorinated than the homopolymer. The copolymers eliminate HCl at rates that could only be interpreted in terms of styrene group activation. However, the elimination rate fell too rapidly with reaction extent to be accounted for by concentration changes or weak links and was consistent with retardation by the reaction products. The elimination was a radical process and accompanied by chain scission and crosslinking in competition.
Part II. Pyrolysis of a tetrafluoroethylene–acrylonitrile copolymer
Authors: Fock J. 
Published: April 2003

AbstractThe pyrolysis of copolymers obtained by radiation‐induced grafting of acrylonitrile onto polytetrafluoroethylene has been studied. Infrared spectroscopy shows disappearance of CN and appearance CN absorptions, indicative of the conjugation of the nitrile groups in the polyacrylonitrile segments. Aromatization is suggested by the appearance of aromatic CH absorption and by the disappearance of aliphatic CH absorption in the infrared spectra, as well as by the decrease of the C/H ratio and the constancy of the N content during exposure to 280°C. shown by elementary analysis. Melting and remelting was studied by differential thermal analysis with respect to temperature, extent, and shape of peak area. An increase in the melting temperature proportional to the content of acrylonitrile in the copolymer was explained in terms of entropy effects. The melting peak obtained after grafting appears as a doublet. The latter disappears after annealing for 14 hr. at 300°C. and does not reappear on crystallization or on remelting. In addition, the areas obtained on first and repeated meltings shows a decrease which is proportional to the content of grafted polyacrylonitrile. These results are taken as an indication of an exothermic reaction involving crosslinking. The rate of disappearance of the CN absorption reaches a maximum at the melting temperature. It seems that the exothermic reaction occurring in the crystalline region is identical with “propagation crosslinking” suggested by Grassie and Hay. It is concluded that an interesting new type of polymeric material has been found.
The preparation of polysiloxane–vinyl monomer graft and block copolymers
Authors: Minoura Yuji , Shundo Minoru , Enomoto Yasushi 
Published: April 2003

AbstractIn another paper the radical polymerization of styrene in the presence of various chlorosilanes was investigated, and polystyrenes having chlorosilyl groups as endgroups were obtained. In the present work attempts were made to obtain polysiloxane styrene graft and block copolymers from chlorosilyl polystyrenes. Block copolymers were obtained with dichlorosilane and graft copolymers with tri‐ and tetrachlorosilanes. In the latter case the insoluble fractions increased, if a suitable stopper, such as butanol or trimethylchlorosilane [(CH3)3SiCl], was not used in the condensation reaction. Methyldichlorosilane was used for the preparation of the graft copolymer, because the SiH bond was more effective than the SiCl bond for the chain transfer reaction.
Molecular weight distribution of liquid poly(ethylene glycols): Determination by gas chromatography
Authors: Fletcher J. P. , Persinger H. E. 
Published: April 2003

AbstractThe molecular weight distribution of liquid polyethylene glycols 200, 300, and 400 can be determined by gas chromatography by using trimethylsilyl ether derivatives. The relative response factors for the first five members of the homologous series were determined experimentally. Attempts are made to extrapolate the experimental data to relative response factors for higher members of the homologous series.
Polymerization of isocyanates. III. Chemical behavior and structure of polyisocyanates
Authors: Iwakura Yoshio , Uno Keikichi , Kobayashi Norio 
Published: April 2003

AbstractThe chemical behavior of polyisocyanates was investigated. Dissociation of the polymer to the monomer was observed directly by infrared spectra. Aminolysis of the polymer gave cyclic trimer and asymmetric urea as reaction products, and the formation of the latter was ascribed to the reaction of amine with the monomer dissociated from the polymer. It was concluded that polyisocyanates are composed of disubstituted amide structure only.
Aromatic polydiketopiperazines
Authors: Iwakura Yoshio , Izawa Shin‐Ichi , Hayano Fusakazu 
Published: April 2003

AbstractAromatic polydiketopiperazines have been prepared from bis‐2‐chloroacetamides of aromatic diamines in the presence of an epoxide as HCl acceptor and a quaternary ammonium halide catalyst. The structures of the polymers were characterized by infrared and NMR spectra. These polymers were soluble in organic acids such as formic acid, dichloroacetic acid, and trifluoroacetic acid but insoluble in common organic solvents such as dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. Thermogravimetric analysis indicated that these polymers decomposed at 300–340°C.
Infrared studies of stereoregular polymerization of methyl methacrylate and methacrylonitrile by organometallic compounds
Authors: Fujimoto Taketoshi , Kawabata Nariyoshi , Furukawa Junji 
Published: April 2003

AbstractInfrared spectra of reaction mixtures of methyl methacrylate or methacrylonitrile with an equimolar amount of organometallic compounds were investigated in relation to the stereoregulating ability of the catalysts in polymerization. It was found that the carbonyl or nitrile stretching frequency correlated with the stereoregularity of polymers prepared with the corresponding catalysts; i.e., the higher the frequency, the higher the isotacticity. From these results a mechanism of isotactic polymer formation was proposed, in which catalyst counterion was located near the carbonyl group in polymer terminal and that of monomer to be reacted, and consequently the isotactic polymerization is facilitated.
Contribution to the study of the mechanism of curing of unsaturated polyester resins
Authors: Fijolka Paul , Shahab Yousif 
Published: April 2003

AbstractThe mechanism of copolymerization of monomethyl and dimethyl maleates and fumarates with styrene was studied by analysis of the conformation of the acid units of the resulting copolymers. The absorption bands for CO stretching and OH stretching in the spectra of the copolymers are fully identical. They are quite different from the spectra of the copolymers obtained from maleic anhydride and styrene that are subsequently treated with absolute methanol to give the monoester which is then esterified with diazomethane to give the diester. The acid units of the copolymers derived from maleic anhydride exist in a gauche configuration; copolymers derived from fumaric units exist in a trans conformation. The identity of copolymers derived from maleic units with those derived from fumaric units but not with those derived from maleic anhydride indicates that the first step in the copolymerization of the maleic units is an isomerization to fumaric units, which are actually the genuine comonomers.
Investigation of reactions in carboxyl‐terminated polybutadiene and tris‐[1‐(2‐methyl)aziridinyl] phosphine oxide
Authors: Strecker R. A. , Tompa A. S. 
Published: April 2003

AbstractThe functionalities of a series of carboxyl‐terminated polybutadiene samples (CTPB) were calculated from an infrared spectroscopic study of the samples reacting to the gel point with tris‐[1‐(2‐methyl)aziridinyl] phosphine oxide (MAPO), Epon X801, and glycerol. Identical functionalities were calculated when Epon X801 and glycerol were used as curing agents. Higher functionalities for CTPB with MAPO were due to additional reactions that MAPO underwent with hydroxyl groups and water, present in carboxyl‐terminated polybutadiene, and with itself (homopolymerization). Rate constants were calculated for the homopolymerization of MAPO in Nujol, in nonfunctional polybutadiene, and in CTPB. The homopolymerization resulted in an increase and then a gradual decrease in MAPO functionality, which was in agreement with that predicted from theoretical considerations.
Preparation and copolymerization of vinyl 10,11‐epoxyundecanoate
Authors: Chow Roberta C. L. , Marvel C. S. 
Published: April 2003

AbstractVinyl 10,11‐epoxyundecanoate has been copolymerized with vinyl chloride and vinyl acetate to give film‐forming copolymers which are readily converted to insoluble materials.
Monomer reactivity ratios for the copolymerization of styrene with 1,2,4‐trivinyl and p‐divinylbenzenes
Authors: Wiley Richard H. , Ahn Tae‐Oan 
Published: April 2003

AbstractThe copolymerization kinetics of 1,2,4‐trivinylbenzene (TVB) with styrene do not clearly resemble those of o‐, m‐, or p‐divinylbenzene (DVB), structural elements of which are present in TVB. A control determination of the reactivity ratios for the styrene‐p‐DVB pair under different conditions (70°C., pre‐gel point conversion), run for comparison with the TVB data, show values (r1 = 0.77; r2 = 1.46) similar to those previously recorded (r1 = 0.77; r2 = 2.08).
Electron spin resonance study of the radiation‐induced polymerization of N‐vinylcarbazole
Authors: Ayscough P. B. , Roy A. K. , Croce R. G. , Munari S. 
Published: April 2003

AbstractWhen crystals of N‐vinylcarbazole are γ‐irradiated at 77°K., the ESR spectrum observed before warming consists of three peaks attributed to a radical–cation with the unpaired spin associated mainly with the nitrogen atom. Above 90°K. polymerization occurs, initiated by the cation, and the spectrum changes to that of an alkyl type of radical, NĊHCH2, trapped in the polymer. Single crystals were used for a detailed analysis of the nuclear hyperfine parameters of the observed radicals.