bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal polymerization of styrene in the presence of some ferrocene derivatives. II. Low concentrations of vinylferrocene and ethylferrocene
Authors: Tinker A. J. , George M. H. , Barrie J. A. 
Published: April 2003

AbstractStyrene has been polymerized thermally at 60°C in the presence of low concentrations of vinylferrocene and in the presence and absence of 2,2′‐azobisisobutyronitrile (AIBN). The polymerizations were studied in bulk and also in benzene solution. The thermal polymerization of styrene in the presence of ethylferrocene, but without added AIBN or solvent, was also examined. The bulk polymerizations exhibited high initial rates of polymerization followed by a decrease in rate. Initial rates of polymerization for bulk polymerizations in the absence of AIBN have been interpreted by means of a kinetic scheme involving propagation with styrene participating in a specific interaction with the ferrocene derivative and some kinetic parameters associated with this scheme have been evaluated. The decrease in the rate of polymerization is due to the formation of a retarder. The benzene solution polymerizations fitted a simple kinetic scheme and the transfer constant for vinylferrocene with respect to polystyryl radicals Cs, has been evaluated as 1.98 × 10−3.
Formation of free radicals in photoirradiated cellulose. VI. Effect of lignin
Authors: Hon Nyok‐Sai 
Published: April 2003

AbstractThe effect of lignin on free‐radical formation in photoirradiated pulp was studied by means of electron spin resonance spectroscopy. Samples were irradiated with light of wavelength longer than 3400 Å as well as longer than 2537 Å. Radical formation in aspen lignin was observed before and after irradiation with light of wavelength longer than 3400 Å. Upon irradiation, free radicals were formed in a pulp sample with 0% lignin content only when oxygen was present. On irradiation with light longer than 2537 Å, in the presence of nitrogen, oxygen, and under vacuum, free‐radical formation was found in all cases. The largest concentration of radicals was obtained under vacuum, the smallest in oxygen. It is evident that cellulose was protected from radiation by the presence of lignin. Increased aspen lignin content in pulp led to a decrease in the relative signal intensity of ESR spectrum, that is, a decrease of the yield of free radicals in the cellulose fraction in pulp. Irradiation with light in the presence of oxygen caused significant yellowing of the pulp sample, and these photooxidation and discoloration reactions occurred primarily on the surface of the sample irradiated.
Nonoxidative crosslinking reactions in natural rubber. I. Determination of crosslinking groups
Authors: Burfield D. R. , Gan S. N. 
Published: April 2003

AbstractThe presence of both epoxide and amine groups as integral constituents of the natural rubber macromolecule have been demonstrated, by application of an HBr double titration technique. The number of such groups is dependent on the clonal source of the rubber and is found to decrease on storage in step with an increase in the plasticity of the rubber. The groups are believed to be involved in nonoxidative crosslinking reactions which occur in rubber on storage. Possible crosslinking mechanisms are proposed.
Synthesis of polyhydrazides by ring‐opening polyaddition reaction of N,N′‐biisomaleimide with dihydrazine and dihydrazides
Authors: Ueda Mitsuru , Kanno Susumu , Imai Yoshio 
Published: April 2003

AbstractThe ring‐opening polyaddition reaction of N,N′‐biisomaleimide with a dihydrazine and dihydrazides was carried out in polar aprotic solvents at room temperature to afford a new class of polyhydrazides having inherent viscosities in the range of 0.1–0.5 in nearly quantitative yields. Almost all of the polyhydrazides were soluble in dimethylformamide, dimethyl sulfoxide, and other polar aprotic solvents. They did not show any clear melt temperature and began to decompose at around 200–300°C.
Isobaric temperature dependence of radical generation in poly(methyl methacrylate)
Authors: Szőcs F. , Plaček J. , Borsig E. 
Published: April 2003

AbstractIn this study the effect of temperature on the generation of free radicals accompanying the decomposition of benzoyl peroxide in poly(methyl methacrylate) was studied. The concentration of the chain‐end radicals was determined by the ESR method. The known nine‐line spectrum of the chain‐end radicals of poly(methyl methacrylate) was observed. This spectrum was affected by the contribution of chain radicals at higher temperatures. The dependence of the chain‐end radical concentration on the annealing temperature of polymer found for different pressures gives information on the conditions under which free radicals arise and decay in the temperature range between 90 and 170°C at pressures ranging from 2000 to 12000 atm.
Polyamide‐imides from 3′,4′‐dicarboxy‐4″‐chloroformyl terephthaloylphenone anhydride
Authors: Tagle L. H. , Neira J. F. , Diaz F. R. , Ramirez R. S. 
Published: April 2003

AbstractNovel polyamide‐imides were prepared from 3′,4′‐dicarboxy‐4″‐chloroformyl terephthaloylphenone anhydride and various aromatic and aliphatic diamines. The polymers were characterized by viscosity, infrared spectra, TGA, DSC, and elemental analysis. The thermal stability of the films was comparable to that of polyamide‐imides previously reported.
Polymerization of alkylene oxides with aluminum alkyl–strong phosphoric acid–lewis base catalyst
Authors: Kida Yasuji , Miura Yuichi , Shikata Kazuo , Azuma Keiichi 
Published: April 2003

AbstractPolymerization of epichlorohydrin (ECH) and copolymerization of propylene oxide–allyl glycidyl ether were studied by using a catalyst consisting of aluminum alkyl–strong phosphoric acid–Lewis base. This system showed high polymerization activity for alkylene oxides, and it was elucidated by x‐ray diffraction analysis that the resultant ECH polymer was completely amorphous. The polymerization was presumed to be of the coordinated anionic type. The physical properties of the vulcanized polymers were studied.
Temperature‐induced transformations of peroxide radicals formed in polytetrafluoroethylene with γ‐ray irradiation
Authors: Tagawa Tōru , Amemiya Hideo , Shinohara Isao , Hagiwara Miyuki , Kagiya Tsutomu 
Published: April 2003

AbstractAt 200°C, temperature‐induced transformations of peroxide radicals from CF2CF(OO·)CF2 (radical I) to CF2CFCF2 (radical 1) and CF2CF2OO· (radical II) to CF2CF2 (radical 2) in vacuo, and from I to II in oxygen atmosphere were observed. In these thermal transformations, the evolution of CO2 with a small amount of CO and CF2O was observed. Further, measurements of the heat of crystallization of the treated polytetrafluoroethylene suggest that a reduction of polymer molecular weight occurs during the transformations from I to 1 and I to II.
Inorganic coordination polymers. XVIII. Observations on brittle and flexible films of {Cr[OP(CH3)(C6H5)O]2[OP(C8H17)2O]}x
Authors: Nannelli Piero , Gillman H. D. , Block B. P. 
Published: April 2003

AbstractFilms of {Cr[OP(CH3)(CH6H5)O]2[OP(C8H17)2O]}x, formed during the reaction of {Cr(OH)[OP(CH3)(C6H5)O]2}x with dioctylphosphinic acid, are either brittle or flexible depending on the details of the preparation of the chromium(III) bisphosphinate precursor. Both kinds of film appear to contain mainly triple‐bridged chains. Differing degrees of randomness in distribution of the two kinds of phosphinate bridges and, hence, of the internally plasticizing octyl groups along the chain account for the observed differences in flexibility, x‐ray diffraction patterns, and birefringence. The observed intrinsic viscosities of 9–18 dl/g indicate that these trisphosphinates form microgels rather than true solutions. The thermal degradation of these films proceeds by the oxidation and cleavage of the organic side groups. Addition of antioxidants to the flexible films significantly increases the longevity of their flexibility at 200°C.
Study of radiation‐induced polymerization of vinyl monomers adsorbed on inorganic substances. IV. Dose rate and temperature dependences in the styrene–silica gel system
Authors: Fukano Kazuyuki , Kageyama Eiichi 
Published: April 2003

AbstractIn order to elucidate the mechanism of radiation‐induced polymerization of styrene adsorbed on silica gel, the effects of dose rate and irradiation temperature were studied in detail. Monomer conversion increased with increasing dose rate and temperature. At the same conversion, the percent grafting increased with decreasing dose rate and also with increasing temperature. In general, GPC spectra of graft polymers and homopolymers showed two peaks; the ratio of the two peaks changed with dose rate and irradiation temperature. The dose‐rate exponents of the polymerization rate of four peaks were different from each other. The activation energies of radical polymerization and cationic polymerization were about 2.6 kcal/mole and 0 kcal/mole, respectively. Based on the results obtained, a reaction mechansim is proposed.
Polymer degradation during radiation‐induced emulsion polymerization of styrene
Authors: Sato K. , Rudin A. , Huang R. Y. M. 
Published: April 2003

AbstractStyrene was polymerized in emulsion with initiation by γ‐rays at a dose rate of 0.6 Mrad/hr. Polymerization rates were as expected from previous reports by others. No branching or crosslinking was detectable, and the Mw/Mn ratio of the polystyrene did not change significantly during the course of the polymerization reaction. The molecular weight of the product polymer decreased with increasing conversion, in contrast to the behavior of chemically initiated emulsion polymerizations. Monomer‐free polystyrene does not degrade under the same radiation conditions, and the progressive decrease of polymer molecular weight with conversion is shown to result from the presence of monomer.
Siloxane‐modified heterocyclic polymers
Authors: Breed L. W. , Wiley J. C. 
Published: April 2003

AbstractFully aromatic, siloxane‐modified polybenzimidazoles and polybenzoxazoles were prepared by a single‐stage melt polymerization and characterized. These polymers, which have good solubility in pyridine and N‐methylpyrrolidinone, undergo thermooxidative decomposition above 300°C. Model compounds for these two classes as well as polypyromellitimides were also prepared.
Effect of gegen ion in cationic polymerization and copolymerization of trioxane
Authors: Chen Catherine S. Hsia 
Published: April 2003

Abstractp‐Chlorophenyldiazonium hexafluorophosphate
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has been reported to be a superior catalyst for cationic polymerization and copolymerization of trioxane as compared to boron trifluoride dibutyl etherate (BF3·Bu2O)1. In the present investigation the effect of anions derived from elements in Group VA, AsF and SbF, has been ascertained. It has been concluded that p‐chlorophenyldiazonium hexafluoroarsenate
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is also a superior catalyst to boron trifluoride dibutyletherate (BF3·Bu2O), while p‐chlorophenyl‐diazonium hexafluoroantimonate
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is inferior.Copolymers with the highest polymer yield (>95%) and molecular weight (intrinsic viscosity = 4 to 5) were obtained with
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Simple dependences on catalyst concentration have been observed to hold for a wide catalyst concentration range ([M]/[C]) = (1 to 20) × 105:

For
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the same relationships hold. However, the polymer yield (75%) and molecular weights (intrinsic viscosity ≃1) are considerably lower while the extent of chain transfer is higher. Furthermore, the polymerization proceeds with explosive violence.The quantitative aspects resulting from polymerization, for the most part, can be interpreted in terms of the extent of dissociation of the propagating ions.
Degradation of polymer mixtures. VI. Blends of poly(vinyl chloride) with polystyrene
Authors: Dodson B. , McNeill I. C. 
Published: April 2003

AbstractThe degradation of films containing both PS and PVC has been examined by TVA and TG. Stabilization of both polymers, more notably PS, is observed, but the degradation products are the same as when the polymers are degraded alone. Molecular weight measurements indicate a more rapid decrease in the molecular weight of PS when PVC is present. The possibility of grafting or other processes leading to chlorine incorporation in PS has been excluded by the results of experiments using 36Cl‐labeled PVC. The mechanisms of possible interactions between the degrading polymers are discussed. Processes involving reaction of chlorine radicals with PS at lower temperatures and reaction of PS radicals with the residue of PVC dehydrochlorination or its decomposition products at higher temperatures appear probable.
Urea‐formaldehyde resins: NMR study on base‐catalyzed reaction of formaldehyde with urea in deuterium oxide
Authors: Tomita Bunichiro , Hirose Yoshiyuki 
Published: April 2003

AbstractHigh‐resolution nuclear magnetic resonance has been used in order to investigate the base‐catalyzed reaction of formaldehyde with urea in deuterium oxide. We investigated the effects of temperature and concentration on the chemical shift of glycol species in formalin under basic condition. Assignment of all the signals appearing in the addition reaction was completed. The formation of N,N‐dimethylolurea, uron, monomethyloluron, and dimethyloluron was observed for the first time, as well as the formation of monomethylolurea, N,N′‐dimethylolurea, and trimethylolurea, which had been observed previously: the formation of presumptive tetramethylolurea could not be observed. The rate constants and equilibrium constant for urea, monomethylolurea, N,N′‐ and N,N‐dimethylolurea, and trimethylolurea were estimated by analysis of the decomposition reactions of monomethylolurea and N,N′‐dimethylolurea.
Determination of interaction parameter χ1, for poly(vinyl alcohol) and water in gels crosslinked from solutions
Authors: Peppas Nikolaos A. , Merrill Edward W. 
Published: April 2003

AbstractThe Flory interaction parameter χ1 of poly(vinyl alcohol)‐water systems has been estimated as a function of temperature and volume fraction of PVA, the polymer having been crosslinked from solutions of the same in water. Values are reported for temperatures between 0°C and 90°C and polymer volume fractions between 0.03 and 0.12.
Free‐radical polymerization of vinylferrocene. II. Spectroscopic and physical properties
Authors: George M. H. , Hayes G. F. 
Published: April 2003

AbstractThe spectroscopic and physical properties of poly(vinylferrocene) prepared by free‐radical polymerization in benzene are discussed. The results obtained in these studies are in accord with the kinetic analysis of the polymerization reactions in benzene. ESR spectroscopy shows that the polymer is paramagnetic and contains a species which is identified by Mössbauer spectroscopy as an ionically bound complex of Fe(III) in a high spin (3d5) configuration. The concentration of this species is shown to be dependent upon kinetic parameters. Magnetic susceptibility measurements show that the polymer does not contain any oxidized ferromagnetic impurities. Infrared spectroscopy indicates that the polymer contains vinylidene groups. The presence of these groups is explained by chain transfer to monomer followed by reinitiation. Ultraviolet spectroscopy also suggests the presence of unsaturation in the polymer. Gel‐permeation chromatography indicates that poly(vinylferrocene) is branched even at low conversions. The effect of transfer reactions and the intramolecular electron transfer termination of the chain radical on the structure of poly(vinylferrocene) is discussed. The glass transition temperature and thermal stability of the polymer are also examined.
Application of ESCA to polymer chemistry. VIII. Surface structures of AB block copolymers of polydimethylsiloxane and polystyrene
Authors: Clark D. T. , Peeling J. , O'Malley J. M. 
Published: April 2003

AbstractThe surface morphology of a number of films of AB block copolymers of polydimethylsiloxane and polystyrene was examined by ESCA and contact angle measurements. In all cases the immediate surface is shown to consist of an essentially pure polydimethylsiloxane component. By comparing the intensities of elastic peaks corresponding to photoionizations from core levels without energy loss for polydimethylsiloxane and polystyrene with those for the block copolymers and by consideration of shake‐up phenomena specific to the polystyrene component, an estimate of the thickness of the polydimethylsiloxane outer layer of the latter may be obtained. This is shown to vary between ∼13 and 40 Å, depending on the method of formation of copolymer film.
Synthesis of light‐sensitive arenesulfonylazido polycarboxylic acids
Authors: Ulrich Henri , Stuber F. A. , Peters G. M. , Sayigh A. A. R. 
Published: April 2003

AbstractSeveral light‐sensitive arenesulfonylazido polycarboxylic acids were synthesized by a one‐step reaction of a polymeric anhydride with a light‐sensitive monofunctional alcohol, or by the reverse reaction, i.e., reaction of a polymeric alcohol with a light‐sensitive monofunctional anhydride. The polycarboxylic acids are soluble in polar organic solvents and in aqueous base. Neutralization of part of the carboxyl groups gives rise to the formation of water‐soluble polymers. Coreaction of poly(maleic anhydride‐co‐methyl vinyl ether) with 2‐hydroxyethyl 4‐sulfonylazidocarbanilate and 2‐hydroxyethyl trans‐2,5‐dimethoxystilbene‐4′‐carbamate produces a light‐sensitive polycarboxylic acid with “built‐in” sensitizer.
Anionic polymerization. IV. Effect of crown ethers on alkylsodium initiator
Authors: Cheng Tai Chun , Halasa Adel Farhan 
Published: April 2003

AbstractThe polymerization of butadiene and copolymerization of butadiene‐styrene with alkylsodium catalyst modified by crown ethers in hydrocarbon solvent has been investigated. This catalyst system produced polybutadiene of high viscosity (2.0–5.0) and high vinyl content (80%) in high conversion (75–95%). These results are in contrast to those obtained with aliphatic ether‐modified alkylsodium polymerization which typically gives products of low molecular weight and at low conversion. The copolymerization of butadiene‐styrene with alkylsodium catalyst modified by crown ethers gave a copolymer which did not contain block styrene. Although the copolymer did not contain block styrene, there was an unusually high level of incorporation of styrene in the copolymer at low conversion. This behavior is quite different from either modified organolithium or unmodified organosodium initiators, in which the styrene is uniformly and randomly incorporated along the chain.
Polymerization of coordinated monomers. XI. Structure and reactivity of the ternary molecular complex composed of stannic chloride, methyl methacrylate, and styrene
Authors: Komiyama Makoto , Hirai Hidefumi 
Published: April 2003

AbstractThe time‐averaged orientation of styrene in the ternary molecular complex composed of stannic chloride, methyl methacrylate, and styrene was determined by use of the chemical shift changes of the protons in the methyl methacrylate on the ternary molecular complex formation. The observed chemical shift change for each of the protons in the methyl methacrylate is expressed by the weighted average of the shifts due to the anisotropic shielding of the benzene ring of styrene for conformations I and II, using the common statistical weight. Conformations I and II correspond to the cis and trans rotational isomers, respectively, of methyl methacrylate with respect to the rotation of the methoxymethyl group around the carbonyl carbon‐ether oxygen bond. Extended Hückel calculations were made on the methyl methacrylate monomer coordinated to stannic chloride and styrene monomer as well as the growing radicals corresponding to the monomers. The energy levels of the frontier orbitals of the species were determined by use of the ionization potentials, the absorption maxima, and the results of the extended Hückel calculations. The high reactivity of the ternary molecular complex is discussed in terms of the interactions between the frontier orbitals of the styrene and those of the coordinated methyl methacrylate.
Synthesis of polyphthalamides by ring‐opening polyaddition reaction of N,N′‐disubstituted bisphthalisoimides with diamines
Authors: Ueda Mitsuru , Kanno Susumu , Imai Yoshio 
Published: April 2003

AbstractThe ring‐opening polyaddition reaction of N,N′‐disubstituted bisphthalisoimides with various diamines in amide‐type solvents at room temperature afforded polyphthalamides having inherent viscosity of up to 0.26 in excellent yields. Some of the polymers thus obtained are a new class of ordered alternating copolyphthalamides. These polyamides were soluble in polar aprotic solvents, as well as in acidic solvents. They showed relatively low melt temperature in the range of 120–220°C and further low level of thermal stability.
Free radicals in γ‐irradiated poly‐α‐methylstyrene
Authors: Mawaziny Sheila , Arafa Salah , Iskandar Magdy F. , El‐Subee Maher Z. 
Published: April 2003

AbstractElectron spin resonance (ESR) spectra were observed at −160°C and at room temperature for γ‐irradiated poly‐α‐methylstyrene. The spectrum observed at room temperature has been attributed to the radical species while that at −160°C results from the same radical and superposition of the spectrum due to the radical ĊH2‐C(CH3)(C6H5)‐. The radicals which are stable at room temperature could be used to graft vinyl acetate.
Chain scission efficiency of some polymers in γ‐radiation
Authors: Ouano A. C. , Johnson D. E. , Dawson B. , Pederson L. A. 
Published: April 2003

AbstractThe G values of poly(methyl methacrylates) (PMMA), polycarbonates, and a polylactone for γ‐radiation were determined by using a computer‐assisted GPC as the primary tool for the measurement of the number‐average molecular weights M̄n. The accuracy and precision of the automated GPC were found to have a normalized standard deviation (σ/M̄n) of less than 7%. The G value of PMMA was determined to be essentially independent of molecular weight. For low molecular weight polymers, some nonlinearity in the I/M̄n versus dosage plot was observed at low dosage, i.e., about 1 Mrad.
Polymerization of hexamethylcyclotrisiloxane with a biscatecholsiliconate. I. Nature of polymerization
Authors: Lee C. L. , Johannson O. K. 
Published: April 2003

AbstractPolymerization behavior of hexamethylcyclotrisiloxane (D3) in toluene solution with the use of benzyltrimethylammonium bis(o‐p;henylenedioxy)phenylsiliconate as a catalyst, dimethyl sulfoxide as promoter, and adventitious moisture as initiator was investigated. The polymerization system gives a linear difunctional polymer, HO(Me2SiO)xH, with a molecular weight which is inversely proportional to the amount of water reacted rather than to the amount of catalyst employed. The polymerization in the presence of H2O gives rise to molecular weight distributions very close to Poisson distributions. The normalized experimental GPC curve agrees very well with the theoretical GPC curve calculated from the polymerization scheme:
\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm H}_2 {\rm O} + ({\rm Me}_2 {\rm SiO})_3 \to {\rm HO}({\rm Me}_2 {\rm SiO})_3 {\rm H}} \\ {{\rm HO(Me}_{\rm 2} {\rm SiO)}_{\rm 3} {\rm H} + {\rm N(Me}_{\rm 2} {\rm SiO)}_{\rm 3} \to {\rm HO}({\rm Me}_2 {\rm SiO})_{3(n + 1)} {\rm H}} \\ \end{array} $$\end{document}
Polymerization carried out in the combined presence of H2O and ROH, where R is Me or Me3Si, gives rise to bimodal molecular weight distributions. The resulting polymers consist of HO(Me2SiO)2xH and RO(Me2SiO)xH. The molecular weight of the former is twice that of the latter, and their proportion depends on the ratio of H2O to ROH. The system is a special type of “living” polymer.