bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some problems of nonequilibrium copolycondensation
Authors: Korshak V. V. , Vinogradova S. V. , Vasnev V. A. , Perfilov Yu. I. , Okulevich P. O. 
Published: April 2003

AbstractThe influence of the reactivity of the starting compounds and reaction conditions on the formation of the macromolecules of copolymers has been investigated for a nonequilibrium copolycondensation in solution by acceptor‐catalytic polyesterification. In the nonequilibrium copolycondensation in solution, copolymers with different distributions of units may be formed, depending on various factors. Introduction of all amounts of acid chloride (intermonomer) in the beginning of the nonequilibrium copolycondensation leads to the formation of copolymers with statistical distribution of the units independent of the difference in reactivity of the comonomers used. For synthesis of copolymers with a block structure by one‐stage nonequilibrium polycondensation in solution the initial comonomers must have different reactivities (r ≠ 1) and the rate of intermonomer introduction must be lower than that of its reaction with the more reactive comonomer. On varying the above factors, block copolymers with different lengths of block segments may be obtained.
Radiation‐induced polymerization of cyclohexene sulfide in the solid state
Authors: Hiramoto Tetsuo , Nishii Masanobu , Fiala Vladimir , Yamaoka Hitoshi 
Published: April 2003

AbstractRadiation‐induced solid‐state polymerization of cyclohexene sulfide has been investigated. Differential thermal analysis shows that this compound has a phase transition point at −74°C and behaves as a plastic crystal in the temperature range from −74 to −20°C (melting point). By rapid cooling, this plastic crystal was easily supercooled, and below −166°C a glassy crystal, i.e., a supercooled nonequilibrium state of plastic crystal, was obtained. In‐source polymerization proceeded in the plastic crystalline state. Postpolymerization of glassy crystalline monomer irradiated at −196°C occurred above −166°C (glass transition point) during subsequent heating.
Adsorption of polymers at the solution–solid interface. IX. Solution adsorption of nitrile rubbers on silicas
Authors: Clark P. J. , Howard G. J. 
Published: April 2003

AbstractThe adsorption of three acrylonitrile–butadiene random copolymers from two solvents has been studied: two pyrogenic silicas of differing surface areas, which had received several surface modifications, were used as adsorbents. Infrared spectroscopic studies confirm that the nitrile groups bond to the silica surface. The amount of copolymer adsorbed is related to the acrylonitrile content, which also controls the copolymer solubility: adsorptions are higher from benzene than from a better solvent, trichloroethylene. Vapor sorption of model compounds indicate how the adsorbent surface area and surface composition affect monolayer capacities: heats of adsorption are not markedly altered by the adsorbent modifications.
Poly‐α‐ester degradation studies. III. Effect of β‐chlorination on polymer degradation
Authors: Patterson A. , Sutton G. J. , Tighe B. J. 
Published: April 2003

AbstractThe thermal degradation of two β‐chlorinated versions of poly(isopropylidene carboxylate) has been studied by the combined thermogravimetric and gas evolution techniques described previously. Poly(3‐chloro‐2‐methyl‐2‐hydroxypropionic acid) was found to decompose by a predominantly first‐order process which was characterized by kinetic parameters similar to those obtained for poly(isopropylidene carboxylate). These are interpreted in terms of an intramolecular ester‐exchange process. As the reaction proceeds intermolecular elimination of hydrogen chloride leads to crosslinking and ultimately to the formation of a carbonaceous char. This process is much more marked in the randomly β‐chlorinated analog of poly(isopropylidene carboxylate). With this polymer, drastic deviation from first‐order behavior is observed in thermogravimetric results, even in the early stages of reaction. Gas evolution analysis, being more influenced by degradation fragments having an appreciable vapor pressure, yields reasonable first‐order data and indicates that the intramolecular interchange mechanism is still an important process. In general, the introduction of β‐chlorine atoms is seen to reduce the rate of thermal decomposition of poly‐α‐esters.
Poly(diphenylsiloxy)arylazines. I. Synthesis and characterization
Authors: Goldsberry R. E. , Adamson M. J. , Reinisch R. F. 
Published: April 2003

AbstractThe synthesis of poly(diphenylsiloxy)arylazines and the preparation of the necessary aromatic aldehyde and azine precursors are described. This new family of polymers was prepared by a modified melt‐condensation reaction of hydroxyl‐substituted phenyl‐and naphthylazines with bis(anilino)diphenylsilane. The resulting polymers have been characterized by elemental analysis, gel‐permeation chromatography, vapor‐phase osmometry, and absorption spectroscopy. Assignment of a polymer backbone composed of alternating diphenylsiloxane and arylazine moieties was made on the basis of the infrared absorption bands and by comparison of the fluorescence and absorption spectra of the polymers with those of model compounds. The molecular weight of the polymers was found to depend on temperature, reaction time, and the ratio of monomers. The formation of low molecular weight products was avoided by maintaining reaction temperatures below the decomposition point of the arylazine and by keeping the ratio of silylamine to arylazine at about 3:1. Molecular weights as high as 38,000 and extents of conversion of 85% were obtained by the described melt condensation procedure. The molecular weight of another member of the family was increased from 4600 to 8100 by a post‐polymerization scheme, involving the reaction of aromatic hydroxyl and anilinosilane endgroups. Significant crosslinking via ortho hydroxyl groups during the polymerization of tetrahydroxyarylazines can be ruled out because of the solubility of the polymers in chloroform or tetrahydrofuran and on the basis of their fluorescence spectrum.
Mechanism of thermal decolorization of benzospirans in some amorphous polymeric matrices
Authors: Kryszewski M. , Łapienis D. , Nadolski B. 
Published: April 2003

AbstractThe photochromic effect has been investigated for three compounds of the benzospiran group dissolved in amorphous polymers: poly(methyl methacrylate), poly(n‐butyl methacrylate), poly(vinyl acetate), and poly(vinyl n‐butyrate). The kinetics of the thermal bleaching reaction above Tg of the matrix follow a first‐order equation due to the averaging of free volume distribution related to the diffusion of segments in viscoelastic state. A more complex mechanism of decolorization below Tg has been considered from the point of view of unequal, discrete distribution of environments in which the photochromic molecules exist in the glassy matrix. A change of the activation energy and the mechanism of color decay on passing through Tg is not a rule (PVB), which shows, that for a polymer having long, flexible chains, secondary glass transition phenomena play a decisive role. In the case of glassy polymers (PMMA), the photochromic effect of benzospirans may be employed to determine Tβ. It seems, that in addition to steric restrictions for trans–cis isomerization in the decolorization process one must consider the interactions of photochromic molecules with the matrix as well as their chemical nature.
Mechanism of alternating copolymerization of polar and hydrocarbon polymers
Authors: Golubev V. B. , Zubov V. P. , Georgiev G. S. , Stoyachenko I. L. , Kabanov V. A. 
Published: April 2003

AbstractRadical copolymerization of butyl methacrylate with 2,3‐dimethylbutadiene in the presence of Al(C2H5)2Cl or ZnCl2 results in alternating copolymers. The nature of active centers and the mechanism of polymerization in these systems have been studied by means of ESR measurements in combination with calorimetry at low temperatures. The active centers are monoradicals propagating by alternative addition of single monomer molecules; thus the reaction can be described in terms of a conventional kinetic scheme of radical additional polymerization. Participation of binary donor—acceptor complexes of the monomers in the reaction has not been confirmed. Similar conclusions have been drawn for the other alternating system studied, maleic anhydride–2,3‐dimethylbutadiene. The feasibility of formation of alternating copolymers in the studied systems by the conventional mechanism of binary radical copolymerization has been confirmed by qualitative quantum‐chemical treatment of the propagation reactions with due account to the donor–acceptor interactions in the transition state.
Polymerization of isoprene initiated by the reaction products of zirconium allylic complexes and titanium chlorides
Authors: Kormer V. A. , Vasiliev V. A. , Kalinicheva N. A. , Belgorodskaya O. I. 
Published: April 2003

AbstractReaction of (all)4Zr with TiCl4 involves the migration of the allyl ligands to titanium which is accompanied by the reduction of titanium to a tri‐ and divalent state and the formation of diallyl. The reaction products are found to initiate polymerization and oligomerization of isoprene. The course of the isoprene reactions and the properties of the resulting polymers are determined by the nature of the complexes formed. The reaction products of TiCl4 or TiCl3 with (all)2ZrCl2 initiate cationic polymerization of isoprene. Complexes resulting from the reaction of TiCl3 with (all)4Zr or (all)3ZrCl lead to cis‐1,4‐polyisoprene.
Regularities of diene copolymerization by coordination catalytic systems and the mechanism of stereoregulation
Authors: Dolgoplosk B. A. , Beilin S. I. , Korshak Yu. V. , Makovetsky K. L. , Tinyakova E. I. 
Published: April 2003

AbstractA study has been conducted of the relative reactivity of a series of dienes (butadiene, isoprene, 2,3‐dimethylbutadiene, cyclohexadiene‐1,3), as well as of butadiene and styrene, in copolymerization by various coordination catalyst systems based on transition metals: nickel, cobalt, titanium, chromium, molybdenum, and tungsten. The microstructure of homopolymers and copolymers of dienes has been investigated. Regularities have been established in the mutual influence of the comonomers on the microstructure of a polymer chain. Experimental data on the influence of the concentration of diene monomer, and electron‐donating and electron‐accepting compounds on the microstructure of polydiene chain have been used in discussing the alternative mechanisms of stereoregulation in diene polymerization by active centers of the π‐allyl type.
Viscosity study of radiation chemistry of polystyrene
Authors: Chau T. C. , Rudin Alfred 
Published: April 2003

AbstractThe effects of γ‐radiation on aqueous polystyrene emulsions were followed by measurements by intrinsic viscosities of soluble polymer in toluene. Estimates of incipient gel dose from intrinsic viscosity data do not coincide closely with those from measurements of gel content. This uncertainty and those in molecular weight averages make it difficult to assign a precise value to G(crosslink), even when the scission crosslinking ratio in the particular system is reliably known. The intrinsic viscosity of sol polymer in the postgel region decreases with increasing dose to an asymptotic value. The decrease is as expected if larger molecules are progressively linked into the gel network and the asymptote may be attributable to cyclization. Present theories of branching do not seem to be applicable for quantitative estimation of scission/crosslinking ratios caused by irradiation of polystyrene. This is probably connected with deficiencies in the theoretical connection between radius of gyration and intrinsic viscosity in good solvents. Diallyl fumarate and diallyl maleate increased crosslinking rates, but only at low doses. Chain scission was enhanced by addition of 1,2‐dichloroethylene and 2,5‐dimethylhexane‐2,5‐dihydroperoxide.
Molecular complexes of sulfur dioxide with organic carbonates
Authors: Rooney M. L. , Best D. J. , Davis E. G. 
Published: April 2003

AbstractSpectroscopic studies made on the bisphenol A polycarbonate–sulfur dioxide system showed evidence of interaction between polymer and penetrant. Equilibrium studies made on solutions of sulfur dioxide and organic carbonates chosen as monomer analogs showed that complexes of the donor–acceptor type were formed, and that at temperatures of 15°C and less the stoichiometry of these was greater than 1:1. The procedures described are compared with those used in other donor–acceptor studies, and the results observed from the equilibrium studies are interpreted by using data reported for other sulfur dioxide–donor systems.
Fibers from polyblends containing nylon 6 as basic component. I. Melt spinning and physical properties of blend fibers
Authors: Kitao Toshio , Kobayashi Hiroshi , Ikegami Seiji , Ohya Seigo 
Published: April 2003

AbstractFive series of two‐component blend filaments, comprising nylon 6 (N6) and nylon 66 (N66), nylon 610 (N610), nylon 11 (N11), nylon 12 (N12), or poly(ethylene terephthalate) (PET), were prepared by using a research spinning machine and a conventional drawing machine. The microstructure and the physical properties of the resultant filaments were evaluated with a tensile tester, a optical microscope, a density‐gradient column, and a DTA instrument. When both components were mixed homogeneously so that they would form a three‐dimensional network, the tensile properties of the blend filament were at least equivalent to the values predicted from those of both components. On the other hand, as in the cases of 30/70 and 70/30 N6–PET, when the minor component was discretely distributed as short fibrils in the matrix of the major component, the blend filament had an extremely weak tenacity. A supertenacity filament was obtained from 50/50 N6–N610. The marked increase of the tensil strength and the initial modulus of 50/50 N6–N610, about 12 g/den and 520 kg/mm2, respectively, may be due to a significant increase in the crystallinity and the orientation of the blend.
Radiation‐induced copolymerization of isobutyl vinyl ether with trichloroethylene
Authors: Du Plessis T. A. , Thomas A. C. 
Published: April 2003

AbstractThe radiation‐induced copolymerization of isobutyl vinyl ether with trichloroethylene was investigated in the temperature range from −50°C to 100°C over a wide range of comonomer compositions. A copolymer was obtained in which the monomers alternate with regularity along the polymer chain over essentially the entire range of comonomer compositions. Both the rate of copolymerization and the number‐average molecular weight of the resulting copolymer were found to depend strongly on the initial comonomer composition. The monomer reactivity ratios were determined and correspond well with calculated values. An apparent activation energy of 3.2 kcal/mole was obtained for the copolymerization process which exhibits a dose rate dependence of 0.72. The number‐average molecular weight was found to be strongly dependent on the irradiation temperature, reaching a maximum value at 5°C.
Inorganic coordination polymers. XII. Chromium(III) tris(phosphinates)
Authors: Nannelli Piero , Block B. P. , King J. P. , Saraceno A. J. , Sprout O. S. , Peschko N. D. , Dahl G. H. 
Published: April 2003

AbstractCohesive films of a series of chromium(III) tris(phosphinates)[Cr(OPRR′O)(OPR″‐R‴O)(OPR*R**O)]y in which the side groups on the phosphorus are alkyl, phenyl, and/or hydrogen groups have been prepared by reaction casting or by hot pressing. The preparative reaction appears to involve conversion of an aquahydroxo or hydroxo chromium(III) bis(phosphinate) to an intermediate hydroxo bis(phosphinate) containing coordinated phosphinic acid followed by an intrachain reaction leading to the tris(phosphinate). Tensile strengths of the chromium(III) tris(phosphinates) range from 100 to 5600 psi, elongations from less than 1 to 100%. Thermogravimetric data indicate that major decomposition occurs at temperatures from 200 to 435°C in air and from 410 to 510°C in nitrogen. Infrared spectra and physical properties are interpreted to support a structure for the chromium(III) tris(phosphinates) which is based on linear, triple‐bridged chains. The presence of octyl or other long alkyl side groups on the phosphorus improves the physical properties, presumably by internal plasticization, but leads to decreased thermal stability.
Alternating copolymerization of dienes with α‐olefins
Authors: Furukawa Junji , Tsuruki Shigenori , Kiji Jitsuo 
Published: April 2003

AbstractAlternating copolymerization of butadiene with several α‐olefins and of isoprene with propylene were investigated by using a mixture of VO(Acac)2, Et3Al, and Et2AlCl as catalyst. The alternating copolymerization ability of the olefins decreases in the order, propylene > 1‐butene > 4‐methyl‐1‐pentene > 3‐methyl‐1‐butene. The study on the sequence of the copolymer of isoprene with propylene by ozonolysis reveals that the polymer chain is reasonably expressed by the sequence \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_{\rm 2} \hbox{--} {\rm CH} \hbox{=\hskip-1pt=} {\rm C(CH}_{\rm 3}) \hbox{--} {\rm CH}_{\rm 2} \hbox{--} {\rm CH(CH}_{\rm 3}) \hbox{--} {\rm CH}_{\rm 2} \rlap{--}]_n $\end{document}. NMR and infrared spectra indicate that the chain is terminated with propylene unit, forming a structure of C(CH3)CH2C(CH3)CH2 involving a vinylene group.
γ‐Radiolysis of ketone polymers. II. γ‐Irradiation of styrene–methyl vinyl ketone copolymers
Authors: Slivinskas J. A. , Guillet J. E. 
Published: April 2003

Abstractγ‐Radiolysis of copolymers of styrene and methyl vinyl ketone shows that the introduction of pendant carbonyl groups markedly increases the G(s) value as compared to the homopolymer of styrene. The G(x) value is only slightly affected. These efficiencies are determined by employing an established statistical theory for random crosslinking and scission coupled with gel‐permeation chromatography as the analytical tool required to follow the changes in the MWD of polymers. Also the G(H2) values are unaltered by the introduction of carbonyl groups in polystyrene. These results are in marked contrast to the effects of carbonyl groups in polyethylene when subjected to γ‐radiolysis and can be attributed to the protective role played by the aromatic phenyl groups in polystyrene.
The influence of fine structure on the pyrolysis of cellulose. II. Pyrolysis in air
Authors: Basch A. , Lewin M. 
Published: April 2003

AbstractThe pyrolysis of purified celluloses in air at 251°C was studied. The pyrolysis was found to obey first‐order kinetics, and the rate constants correlated with the crystallinities, orientations and accessibilities of the samples. The results are interpreted in terms of an oxygen‐catalyzed decomposition, with the accessibility of oxygen to the cellulose determining the rate of pyrolysis. The production of levoglucosan under conditions approaching combustion was shown to be a function of the crystallinity and orientation of cellulose. Some levoglucosan appears to be produced from the less ordered regions.
Polymerization of methyl methacrylate initiated by tri‐n‐butylborane–organic halide systems
Authors: Yoshikuni M. , Asami M. , Iwabuchi S. , Kojima K. 
Published: April 2003

AbstractThe polymerization of methyl methacrylate (MMA) initiated by tri‐n‐butylborane (TBB) was studied in the presence of various organic halides (R′X). It was found that R′X accelerated the polymerization of MMA. Aliphatic halides were more effective than aromatic halides. Cocatalytic effects of butyl halides decreased in the order: n‐BuI > n‐BuBr > n‐BuCl; n‐BuBr ⋍ sec‐BuBr > i‐BuBr > tert‐BuBr. In the polymerization of MMA by TBB‐n‐BuI, the initial rate of polymerization was found to be proportional to the concentration of MMA and to the square root of the concentration of TBB‐n‐BuI. The apparent activation energy was 5.3 kcal/mole. From this and other results, it was assumed that the polymerization of MMA by this initiator system proceeds by a radical mechanism via a weak complex between TBB and R′X; alkyl radicals are formed by the interaction of R′X with TBB. The TBB–R′X system can initiate the polymerization of MMA and AN, but is ineffective in the polymerization of styrene.
Heat‐resistant polymers containing bipyridyl units. I. Polyimides
Authors: Kurita Keisuke , Williams Roy L. 
Published: April 2003

AbstractPolyimides containing bipyridyl units were synthesized. The bipyridyl units were successfully incorporated by polymerization of various bipyridyl diamines with aromatic tetracarboxylic acid dianhydrides. The resulting polyamic acids had inherent viscosities in the range 0.07 to 2.26, and they were converted to the polyimides by thermal cyclization. The polyimides containing the bipyridyl units exhibited varying degrees of solubility in dimethylacetamide and m‐cresol and were found to be very soluble in dichloroacetic acid.
Photo‐copolymerization of methacryloyl‐L‐valine methyl ester, methacryloyl‐D‐valine methyl ester, and maleic anhydride
Authors: Nishihara Koji , Sakota Naokazu 
Published: April 2003

AbstractPhotocopolymerization of methacryloyl‐L‐valine methyl ester (L‐MAVM), methacryloyl‐D‐valine methyl ester (D‐MAVM) and maleic anhydride (MAn) was carried out in dioxane at 25°C without initiator at an initial total concentration of the three monomers of 1 mole/1.; the molar ratio of MAn in the feed to the sum of L‐ and D‐MAVM was 1 : 1 in all cases. The copolymer with a 1 : 1 molar ratio of MAVM and MAn was always obtained regardless of the feed molar ratio of L‐ and D‐MAVM. The circular dichroism (CD) spectra of the copolymer before and after hydrolysis showed a linear relationship between the monomer unit ellipticity at 222 nm and the molar feed ratio of L‐ and D‐MAVM and suggested the induction of an asymmetric center into the polymer main chain. The results also indicated that the configuration of the induced asymmetric carbon atoms would be arranged according to that of fed MAVM monomer.
Reaction of nitrogen dioxide with linear polyurethane
Authors: Jellinek H. H. G. , Wang T. J. Y. 
Published: April 2003

AbstractLinear polyurethane has been exposed to nitrogen dioxide over a temperature range from 15 to 60°C at pressures of 20 and 2 mm Hg, respectively. Normal random‐chain scission of urethane links takes place accompanied by a limited amount of random crosslinking. These crosslinks are eventually irreversibly scissioned again. At the same time, carbon dioxide is evolved, and the infrared spectra of the polymer films change during exposure, indicating disappearance of urethane linkages and formation and decay of nitro and nitroso groups along the polymer backbone. The overall reaction is diffusion‐controlled at least down to a film thickness of 10 μ. All energies of activation of the various processes are relatively small as expected for a diffusion controlled process. Tentative mechanisms have been proposed agreeing well with experimental results.