bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental branching results for diene polymers by use of gel‐permeation chromatography
Authors: Ambler M. R. , Mate R. D. , Purdon J. R. 
Published: April 2003

AbstractBranching analyses in styrene–butadiene rubbers and polybutadiene rubbers have revealed large differences in branching between rubbers polymerized in different ways. The functionalities of several star‐branched solution‐polymerized styrene–butadiene rubbers were calculated and compared to their expected structures. Emulsion‐polymerized polybutadiene rubber and a series of solution‐polymerized polybutadienes made with different catalysts had different degrees of random branching, and evidence is presented indicating that the different available catalyst systems provide some latitude in making rubbers of different branching contents. Random branching analyses on a series of emulsion‐polymerized styrene–butadiene rubbers revealed the dependency of branching on molecular weight and molecular weight distribution. The influence of polymerization temperature on the branching of emulsion‐polymerized styrene–butadiene rubber was also studied.
Polymeric nitrile–palladium chloride complexes and their reaction with olefins
Authors: Kraus M. , Tomanová D. 
Published: April 2003

AbstractPolymers containing cyano groups connected to the polymeric chain by means of at least one methylene group adsorb palladium dichloride reversibly from its slightly acidic solutions and form surface complexes of the probable structure (CH2CN)2PdCl2. These complexes can adsorb gaseous olefins; ethylene is consumed continuously, but adsorption of propylene and 1‐butene reaches saturation. Additional ethylene can be added to the propylene or 1‐butene adsorbate. Hydrolysis of the surface olefinic complexes yields aldehydes, the ethylene complex giving acetaldehyde and butanal, the mixed ethylene–1‐butene complex giving acetaldehyde, butanal and hexanal.
Carbon‐13 NMR spectroscopy of acrylic monomer and Lewis acid complexes
Authors: Furukawa Junji , Kobayashi Eiichi , Nagata Shiro , Moritani Tōhei 
Published: April 2003

Abstract13C NMR spectra of acrylic monomers complexed with a Lewis acid were measured and their electronic structures discussed in relation to their alternating copolymerizability. The β‐carbon of acrylonitrile and methacrylonitrile showed a downfield shift due to the complex formation with the Lewis acid, while the α‐carbon showed an upfield shift and the nitrile carbon showed no significant shift. The degree of shift of olefinic carbons decreased in the following order: AlCl3 > EtAlCl2 > Et1.5AlCl1.5 > Et2AlCl > SnCl4, EtOAlCl2 > Et(EtO)AlCl, which seems to run parallel to the Lewis acidity and acid strength. On the other hand, the chemical shift of olefinic carbons of methyl acrylate, methyl methacrylate, and olefinic diesters was influenced little by complex formation with Lewis acids, whereas the carbonyl and alkoxyl carbons were deshielded significantly by the complex formation. These results are discussed in terms of electron distribution on the carbons and an alternating polymerization mechanism.
A new single‐step process for polybenzimidazole synthesis
Authors: Hedberg F. L. , Marvel C. S. 
Published: April 2003

AbstractAromatic benzimidazole polymers have been prepared by reaction of the corresponding tetraamine and diester in refluxing sulfolane or phenyl sulfone. The convenience of using these sulfone solvents together with the good yields, high viscosities and absence of crosslinking make this procedure an attractive new route to this class of polymers. The preparation by this procedure of poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole], poly‐[2,2′‐(p‐phenylene)‐5,5′‐bibenzimidazole], poly[2,2′‐(m‐phenylene)‐5,5′‐di(benzimidazole) ether], and poly[2,2′‐(m‐phenylene)‐5,5′‐di(benzimidazole) ketone] is described.
Photoisomerization of 1,2‐diphenylcyclopropane sensitized by polypeptides containing naphthalene groups in their side chain
Authors: Ueno Akihiko , Toda Fujio , Iwakura Yoshio 
Published: April 2003

AbstractPoly(γ‐1‐naphthylmethyl L‐ and DL‐glutamate) (PNLG and PNDLG) and copolypeptides of γ‐1‐naphthylmethyl L‐glutamate and γ‐benzyl‐L‐glutamate were used as sensitizers for isomerization of trans‐1,2‐diphenylcyclopropane. Quantum yields relative to that of 1‐methylnaphthalene were measured in dichloroethane (DCE) and dichloroacetic acid (DCA). The relative quantum yield in DCE was smaller than unity for PNLG, but greater than unity for PNDLG and copolypeptides. The result is discussed in terms of increased effective collisional radius and energy trapping by excimer formation. The relative quantum yields in DCA were close to unity except for the copolypeptides of higher γ‐benzyl L‐glutamate content. This suggests that the naphthalene groups act in the same manner as their monomeric counterparts in the random conformation and that the greater proportion of γ‐benzyl L‐glutamate in the copolypeptides lowers the quantum efficiency because trans‐1,2‐diphenylcyclopropane must penetrate through the polymeric medium in order to encounter the excited naphthalene.
Functional monomers and polymers. XIX. Copolymerization of vinyl monomers containing nucleic acid bases
Authors: Takemoto K. , Akashi M. , Inaki Y. 
Published: April 2003

AbstractTaking into account the specific base–base interaction existing between nucleic acid molecules, we studied the free‐radical copolymerization of N‐β‐methacryloyloxyethyl derivative of uracil with that of adenine at 60°C in various solvents. N‐β‐Methacryloyloxyethyltheophylline as well as methyl methacrylate were used also as comonomers. From the data on the rates in different comonomer feed ratios and the r1 and r2 values obtained, copolymerizability was discussed in some detail. The results suggest that the interaction between uracil and adenine bases plays a role in the copolymerization behavior.
Radiation‐induced emulsion copolymerization of tetrafluoroethylene with propylene. IV. Effects of emulsifier concentration and dose rate
Authors: Matsuda Osamu , Okamoto Jiro , Suzuki Nobutake , Ito Masayuki , Danno Akibumi 
Published: April 2003

AbstractRadiation‐induced emulsion copolymerization of tetrafluoroethylene with propylene was carried out by batch operation with an initial molar ratio of tetrafluoroethylene to propylene of 3.0 in the emulsifier concentration range of 0.1 to 3.0% and in the dose rate range of 2 × 104 to 2 × 105 R/hr. The effects of emulsifier concentration and dose rate on the polymerization rate and the number‐average degree of polymerization are discussed in comparison with the Smith‐Ewart theory. The polymerization rate is proportional to the 0.26 power of emulsifier concentration and to the 0.7 power of dose rate. The degree of polymerization is independent of the emulsifier concentration and the dose rate above the critical micelle concentration (CMC) of the emulsifier. These results are not in agreement with the Smith‐Ewart theory. It is explained that the termination reaction is a degradative chain transfer of propagating radicals to propylene. On the other hand, the copolymerization in emulsion occurs either below the CMC or in the absence of emulsifier. Under these conditions, however, it is impossible to obtain a copolymer of high molecular weight at a high rate of polymerization because of the presence of a small number of polymer particles formed and the short interval of chain growth in the polymer particle.
Spectrophotometric investigation of the mechanism of polymerization of isobutylene with vanadium tetrachloride and visible light
Authors: Toman L. , Marek M. , Jokl J. 
Published: April 2003

AbstractThe spectra of n‐heptane solution of VCl4, isobutylene, and their mixture at temperatures ranging from +25 to −80°C in the range of wavelengths from 200 to 2000 nm were investigated. In the region of wavelengths of visible light (400–700 nm) in which the absorption of isobutylene alone and of VCl4 (concentration lower than 2.2 × 10−4 mole/l.) is practically zero, their mixtures exhibit an absorption which depends on the concentration of both components and on temperature. A colored complex of VCl4 and isobutylene is thus obtained, the concentration of which increases with decreasing temperature and is in equilibrium with that of the starting components. The polymerization of isobutylene under the experimental conditions investigated here probably is initiated with the isobutylene–VCl4 complex after its excitation with light or heat. At low temperatures (t < −20°C), when the polymerization of isobutylene with VCl4 virtually does not take place at all in the dark, only excitation with light is operative in the initiation, while at higher temperatures (t > +10°C) thermal excitation plays the predominant role.
Electron spin resonance studies on radiation graft copolymerization in polyethylene. II. Grafting initiated by allyl radicals trapped in irradiated polyethylene
Authors: Seguchi Tadao , Tamura Naoyuki 
Published: April 2003

AbstractThe regions trapping allyl radicals in irradiated polyethylene and the reactivity of the radicals with various monomers have been studied by electron spin resonance. Most of the allyl radicals are trapped in defects or surfaces of the crystallite, and only 10% of the radicals are trapped inside the crystallites. Since the reactivity of the allyl radicals depends on whether they come in contact with reactive monomers, the rate of reaction is related to the concentration of the monomers. When grafting reactions are initiated by allyl radicals, the rate of initiation is rapid and the rate of termination at the initial stage is also very fast. Consequently the yield of grafting increases at the initial stage but soon levels off, which is in contrast to the grafting behavior with alkyl radicals.
Coordination polymers from polycondensates and metal oxides. II. Effect of water molecules on the reactions of polyesters with Mgo and Zno
Authors: Vancsó‐Szmercsányi I. , Szilágyi Á. 
Published: April 2003

AbstractPolyester molecules containing free carboxyl end‐groups react with MgO and ZnO as polydendate ligands to form donor–acceptor complexes, followed by the increase in molecular weight of the original polyester. The role of water in these coordination reactions was studied. It was demonstrated that the water can catalyze the reactions by promoting an ionization effect. In some case it can coordinate to the metal compound and effectively compete with the other ligands present.
Influence of conformational changes of co(III)–poly‐N‐vinyl‐2‐methylimidazole complexes on electron‐transfer reactions of the complexes
Authors: Tsuchida Eishun , Shigehara Kiyotaka , Kurimura Yoshimi 
Published: April 2003

AbstractIn order to study the effect of conformational changes in electron‐transfer reactions of Co(III)–polymer complexes, cis‐[Co(III)(en)2LCl]Cl2, where the ligand L is PVI(poly‐N‐vinyl‐2‐methylimidazole) or NEI (N‐ethylimidazole), was prepared. Electrontransfer reactions with ferrous sulfate or FeEDTA2− were examined mainly with respect to the effects of the degree of coordination, ionic strength, composition of reaction solvent, in relation to the conformational changes. In the reduction by FeEDTA2−, an increase in the degree of coordination of Co(III)–PVI brought about an extreme increase in its reactivity, while it was almost unity in the reduction by ferrous sulfate. With an increase in the ionic strength, the reactivity decreased due to the electrostatic shielding in the reduction by FeEDTA2−. It was noticed that the reaction of Co(III)–PVI was much more enthalpically disadvantageous due to the shrinkage of the polymer chain than that of Co(III)–NEI, when neutral salts were added. In an aqueous alcoholic solvent, an increase in the alcohol concentration accelerated the reaction with FeEDTA2−, and especially in the reaction of Co(III)‐PVI, the maximum and minimum points of the reactivity were observed. On increasing the reaction temperature, the maximum and minimum points shifted to lower alcohol concentration. These phenomena are discussed in regard to the conformational changes of Co(III)–PVI.
Radiation‐induced emulsion polymerization of ethylene. VI. Continuous flow system
Authors: Senrui Shiro , Kodama Atsuro , Takehisa Masaaki 
Published: April 2003

AbstractThe radiation‐induced emulsion polymerization of ethylene in a continuous flow system was carried out at 100°C by using FC‐143 and potassium myristate. The polymer concentration in the latex during the course of the polymerization oscillated several times and then approached a steady‐state value in a few hours in the case of short residence time. The rate of polymerization was almost constant within the residence time range of 0.2–0.9 hr. This is explained by the kinetics assuming the same mechanism previously proposed in the batch system, that is, the number of polymer particles in this range is considered to be constant. Gel formation was observed at longer reaction times in spite of the continuous supply of myristate micelles, possibly because large polymer particles are produced in this stage. The concentration of carbonyl group in the polymer produced by chain transfer to absorbed myristate ion changes in the same way as the polymer concentration with reaction time. The methyl group in the polymer is produced mainly by chain transfer to the polymer, and the concentration is nearly constant during the polymerization except in the initial stage. The rate constants for the continuous polymerization were very different from the batch polymerization previously studied, despite their similarities in nature. The mass transfer rate of the emulsifier from the micelles to the polymer particles requires future study.
Modification of PVC. XXVI. Syntheses and photocrosslinking of polysulfide pendant poly(vinyl chloride)
Authors: Mori Kunio , Harada Hitoshi , Nakamura Yoshiro 
Published: April 2003

AbstractPoly(vinyl chloride) pendant with polysulfide (PS–PVC) having various degrees of substitution, various S substituents, and various numbers of atoms in the sulfur chain has been synthesized by the reaction of poly(vinyl chloride) with a thiol, sulfur, and triethylamine in dimethylformamide at 30°C for 0.4–5 hr. The photocrosslinking reaction has been investigated under ultraviolet irradiation at 250–450 mμ. The photocrosslinking reaction of PS–PVC is influenced by the degree of substitution, the nature of the S substituent, and the number of atoms in the sulfur chain. The degree of photocrosslinking r increased in the order, n‐C4H9 < n‐C8H17 < C6H5CH2 < i‐C3H7 < t‐C4H9. On the photocrosslinking of PS–PVC having two different S substituents, r increases in the similar order for aliphatic substituents and in the order NO2C6H4 < ClC6H4 < C6H5CH2 < CH3C6H4 < t‐C4H9C6H4 < C6H5 for the aromatic substituents. Further, r increases markedly with the increase of sulfur chain number for all PS–PVC. The chemical structure of the crosslinks and the crosslinking mechanism are discussed on the basis of the results.
Photochromic behavior of copolymers of indolinospirobenzopyrane methacrylic derivatives
Authors: Verborgt J. , Smets G. 
Published: April 2003

AbstractThree photochromic 3,3‐dimethyl‐6′‐nitroindolinospirobenzopyran methacrylic derivatives have been synthesized, namely, 1‐methyl 8′‐methacryloxymethyl (A), 1‐(β‐methacrylamidoethyl) (B), and 1‐(β‐methacryloxyethyl) (C). They have been copolymerized with methyl, isobutyl, and n‐propyl methacrylates. The photochromic behavior of these copolymers in the solid state has been compared to that of the homologous isobutyric compounds dissolved in corresponding polymeric matrices. The kinetics of decoloration were resolved in three simultaneous first‐order reactions with rate constants k1, k2, and k3. The influence of the polarity of the polymeric matrix and of the photochrome incorporation has been examined. The rates of decoloration of the copolymers with isobutyl and n‐propyl methacrylate are very sensitive to the glass transition temperature Tg; the activation energy of decoloration increases markedly above Tg, from 19.8 to 36.5 kcal; below Tg the entropy of activation is strongly negative (around ‐20 e.u.), above Tg strongly positive. These effects are interpreted on the basis of an increasing chain segment mobility above Tg.
Inorganic coordination polymers. XVI. Zinc(II) phosphinate polymers containing polyphenylene and poly(phenylene oxide) side groups
Authors: Nannelli Piero , Gillman H. D. , Monsimer Harold G. , Advani Shyam B. 
Published: April 2003

AbstractThe synthesis and characterization of a series of new phosphinic acids and the zinc polymers prepared from them are reported. These compositions are characterized by the presence of short polyphenylene and poly(phenylene oxide) chains as side groups. Some of the zinc derivatives were found to be tractable polymers with good thermal stability.
Photopolymerizations initiated by oxime derivatives
Authors: Il Hong Sung , Kurosaki Toshikazu , Okawara Makoto 
Published: April 2003

AbstractA number of ester, urethane, and carbonate derivatives of biacetyl monooxime, dimethylglyoxime, and ketone oxime, were synthesized and their photolyses studied by means of ultraviolet spectroscopy. Most of the oxime derivatives photolyzed easily upon UV irradiation. Among them, however, only the free radicals formed by photolysis from the ester and carbonate of biacetyl monooxime could effectively initiate the polymerization of a vinyl monomer such as methyl methacrylate. Based on the results obtained from the monomeric reactions, syntheses of grafting polymers were made. Graft polymers were obtained by using a copolymer of methyl methacrylate and methacrylic acid–biacetyl monooxime ester (copolymer I) and that of methyl methacrylate and vinyl benzioc acid–biacetyl monooxime ester (copolymer II) in good yield and without the formation of homopolymer. It was also found that when copolymer I was employed as a grafting polymer, a considerable amount of main‐chain scission was seen, but no chain degradation was noted in the case of copolymer II. Photocrosslinking was attempted by using these copolymers in the presence of divinyl benzene. It was confirmed that copolymer II was photocrosslinkable, whereas copolymer I underwent photodegradation.
Aspects of the synthesis and the properties of linear poly‐2,5‐dimethylbenzylenes
Authors: Peppas Nikolaos A. , Valkanas George N. 
Published: April 2003

AbstractPolydimethylbenzylenes, \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} [C_6 H_2 (CH_3 )_2 CH_2 \rlap{--} ]_n$\end{document}, have been obtained by polycondensation of the monochloromethyl, acetoxymethyl, and methoxymethyl derivatives of p‐xylene, via an acid‐catalyzed reaction in anhydrous acetic acid and in 1‐nitropropane. In the highly ionizing solvent acetic acid, because of ionic depolymerization, chain growth takes the form of an equilibrating polycondensation, of a maximum number‐average molecular weight of 2200. In the noninteracting solvent 1‐nitropropane, the molecular weight distribution is more random, and soluble polymers of number‐average molecular weight up to 3900 are formed. The polycondensation reaction in 1‐nitropropane is also initiated by perchlorate salts, in support of the suggestion of a “hot carbonium ion” propagation mechanism. The results are explained by a cataionic polycondensation reaction, yielding crystalline “living polymers” of high structural purity.
Low‐angle x‐ray estimation of macromolecular parameters of the scattering particles in Agave sisalana
Authors: Ratho T. , Patel A. , Singhal O. P. 
Published: April 2003

AbstractVarious macromolecular parameters of Agave sisalana (sisal) fiber were investigated by the low‐angle x‐ray scattering method. The well known Kratky camera of the latest design was utilized for the experimental measurements. The sample studied was a densely packed colloidal system belonging to a general micelle system, and the theories of Kratky and Kratky and Porod were utilized to estimate the parameters. Pore analysis of the substance yields a value for the specific inner surface of the dispersed phase of 0.406 × 10−1 m2/cm3; the transversal length is the same as the length of inhomogeneity, 107.31 Å, and the length of coherence is 342.21 Å. The air fraction of the scattering particles was found to be 0.01%.
Further studies on the ultraviolet graft copolymerization of maleimide by vapor‐phase method
Authors: Hayakawa Kiyoshi , Kawase Kaoru , Yamakita Hiromi 
Published: April 2003

AbstractGraft copolymerization of maleimide onto polyethylene and ethyl cellulose films by using its sublimation vapor was carried out under ultraviolet irradiation in the presence or absence of air; the effect of air or additives on the grafting reaction and on the nature of the grafted films was investigated. The extent of grafting gradually approached a fixed value, in spite of the continuous ultraviolet irradiation. Air retarded the grafting reaction but did not suppress the reaction nor alter the final extent of grafting. Benzoquinone showed no inhibiting effect on the grafting. The grafted polymaleimide was found to be amorphous, even though ultraviolet irradiation produces a highly crystalline homopolymer in the solid phase as well as in the liquid phase. The results were discussed in comparison with those of the vapor‐phase grafting under γ‐ray irradiation; the reaction is attributed to the vapor–crystal equilibrium of monomer and to the formation of short‐chain crosslinks.
Block polymers from isocyanate‐terminated intermediates. II. Preparation of butadiene–ϵ‐caprolactam and styrene–ϵ‐caprolactam block polymers
Authors: Hergenrother William L. , Ambrose Richard J. 
Published: April 2003

AbstractPolystyrene–nylon 6 and polybutadiene–nylon 6 block copolymers have been prepared from isocyanate‐terminated prepolymers. From extraction and fractionation data the products obtained were found to be mixtures of both homopolymers and pure block copolymer. The polybutadiene–nylon 6 copolymers are extremely pliable at ambient temperatures even at high ϵ‐caprolactam contents (70–80 wt‐%). This is true even though these copolymers show a crystalline melting point at 213°C similar to poly‐ϵ‐caprolactam. Presumably this unusual behavior occurs because of the nature of the synthesis which renders the butadiene portion of these copolymers the continuous phase. Plasticity measurements indicate that pliability is dependent on the molecular weight of the block poly‐ϵ‐caprolactam.
Luminescence from thermally oxidized model amides in relation to nylon 66 degradation
Authors: Allen N. S. , McKellar J. F. , Phillips G. O. 
Published: April 2003

AbstractFluorescence and phosphorescence are observed following the mild thermal oxidation of two model compounds for nylon 66. Both emissions are remarkably similar in structure and in wavelength location to the corresponding emissions normally observed from the commercial polymer. Although the fluorescence could not be characterized, the phosphorescence exhibits several features which are clearly consistent with that of a nπ* carbonyl emission. The role of carbonyl groups in the thermal and photochemical oxidation of nylon 66 is discussed.
Influence of the low molecular weight amides on the dynamic behavior of polymers
Authors: Kotlik P. , Heidingsfeld V. , Zelinger J. 
Published: April 2003

AbstractDependence of the dynamic shear modulus G′ and mechanical damping tan δ was measured for mixtures of low molecular amides with VC/VAc copolymer and polystyrene, respectively. A new secondary relaxation was found, which in some cases depends on content of moisture. The effect of molecular structure and concentration of amide is shown.
Effect of photochemical oxidation on polypropylene phosphorescence
Authors: Allen N. S. , McKellar J. F. , Phillips G. O. , Wood D. G. M. 
Published: April 2003

AbstractPhosphorescence from polyolefins was studied from the aspects of excitation and emission wavelength and lifetime. Effects of photochemical oxidation on polypropylene phosphorescence are discussed in contrast to the effects of thermal oxidation.