bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of solvent polarity and cocatalyst structure in the cationic polymerization of 3,3‐bis(chloromethyl) oxetane
Authors: Penczek I. , Penczek St. 
Published: April 2003

AbstractIn the cationic polymerization of 3,3‐bis(chloromethyl)oxetane induced by BF3 the solvent polarity (toluene, methylene chloride, ethylene chloride, nitrobenzene, and nitromethane) does not influence the ktr/kp ratio, where ktr stands for the rate constant of chain transfer to polymer. Increase of the overall polymerization rate is due mainly to the increase of ki. The application of the steady‐state conditions in which the slow formation of the active centers is compensated by the unimolecular chain transfer to polymer allowed the determination of ktr/kp ratios for several chain‐transfer agents of low molecular weight. Alcohols and ethers of different basicities were used. It was established that the ktr/kp ratio is a linear function of −pKa of the chain‐transfer agents.
Use of carbon suboxide to obtain block and graft copolymers. I. Grafting of carbon suboxide on polyamide 6
Authors: Bukowski Andrzej , Porejko Stanislaw 
Published: April 2003

AbstractPolyamide 6 in the form of film was grafted by gaseous carbon suboxide in the form of toluene solutions. The influence of temperature on the extent of grafting was studied. It was concluded that in a sufficiently high temperature a copolymer of high structure appears. The influence of substances that initiate homopolymerization of suboxide upon the course of grafting reaction was studied. It was found that the substances do not increase the effectiveness of grafting. However a significant increase of effectiveness of grafting is produced by introducing into the reaction environment some small quantities of methanol. By the addition of methanol a graft copolymer of a maximum effectiveness of 43.1% was obtained. The copolymer was subjected to further tests and appeared to be c.l. poly(amide‐6–g‐carbon suboxide). Additional tests indicated that the polyamide film graft with carbon suboxide shows some interesting properties.
A polyamide from anthraquinonediketene
Authors: Dutt Prabir K. , Marvel C. S. 
Published: April 2003

AbstractA polyamide has been synthesized by condensing anthraquinonediketene with m‐phenylenediamine (η = 0.62; 0.5% concentration in dimethylacetamide, 30°C). The polymer was not thermostable but decomposed rapidly above 275°C.
The morphology of the monomer–polymer particle in styrene emulsion polymerization
Authors: Grancio M. R. , Williams D. J. 
Published: April 2003

AbstractA heterogeneous model for the monomer–polymer particle in styrene emulsion polymerization is presented. In this model, the growing particle consists of an expanding polymer‐rich core surrounded by a monomer‐rich shell which serves as the major locus of polymerization. This core‐shell model was suggested by kinetic studies with continuously uniform latices which showed that the systems of interest were of the Smith‐Ewart case II type but that the dynamic—as opposed to equilibrium swelling—particle monomer concentrations were continuously variable. Supporting evidence for the suggested morphology was obtained by electron microscope observation of ultrathin sections of latex particles.
Ethylene polymerization catalysis over chromium oxide
Authors: Hogan J. P. 
Published: April 2003

AbstractA study of the nature of polymerization catalysis over CrO3–silica and of the nature of the polyethylene obtained is presented. A fixed surface chromate (or possibly dichromate) species was shown to be activated for polymerization by an oxidation–reduction reaction with the monomer or with other reactive compounds such as CO. A change in catalyst color from orange to blue occurred simultaneously, and an indigoblue color was present only during ethylene addition, indicating involvement of Cr d orbitals. A spectacular chemiluminescence, due to excitation of oxygen, occurred when CO‐treated catalyst was exposed to air. Active site population and the rate at which each site produced polymer molecules were calculated. A reaction mechanism compatible with the experimental data is depicted.
Double‐bond isomerization and hydrogenation in polyethylene with soluble nickel catalysts
Authors: Witt D. R. , Hogan J. P. 
Published: April 2003

AbstractPolyethylene exhibits an increase in melt viscosity (melt index drop‐off) when subjected to extreme thermal treatment. Although stabilizers and antioxidants do not prevent this change it has been possible to stabilize high‐density polyethylene by isomerization or hydrogenation of the polymer unsaturation. A soluble nickel octoate–triethylauminum complex was an active catalyst system for these reactions. A triethyl‐aluminum/nickel ratio of three appeared optimum for maximum activity. Of particular interest regarding this catalyst system was the fact that the terminal vinyl unsaturation of the polymer had to be isomerized to some internal position before hydrogenation commenced. However, when this catalyst system was impregnated on a predried silica or when butyllithium was substituted for triethylaluminum, both isomerization and hydrogenation occurred simultaneously. The addition of a light olefin such as ethylene to the reaction mixture slowed the overall reaction until most of the ethylene had been hydrogenated. At this point the isomerization–hydrogenation reaction path previously mentioned commenced.
Post‐irradiation free‐radical reactions in poly(ethylene terephthalate)
Authors: Campbell D. , Monteith L. K. , Turner D. T. 
Published: April 2003

AbstractExposure of poly(ethylene terephthalate) to γ‐rays results in the formation of radical I, radical II (tentatively), and to an unassigned radical (III) which is responsible for a
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central peak in the ESR spectrum. It is believed that completely amorphous samples of polymer contain radicals II and III. On heating, the radicals decay, and the relative proportion of radical III increases. The kinetics of the overall decay process were followed by measuring the decrease in peak height with time. After an initially rapid reaction the decay of the radical population conformed to second order kinetics. An Arrhenius plot of the logarithm of specific rate versus 1/T indicated two lines which intersected at 72°C, which is close to the glass transition temperature. The activation energies were 112 kcal/mole above 72° and roughly 25 kcal/mole below 72°C. Reference to reports in the literature suggests that this decay can be explained by long‐range movement of the polymer molecules, even in the glassy solid. The decay of radical I in the crystalline regions of an oriented sample was shown to follow first‐order kinetics. As the decay occurs at temperatures as low as 100°C (the melting point is about 260°C), it seems that decay by normal physical movement is unlikely. The results might be explained by invoking the hypothesis of chemical migration of free radical sites by hydrogen atom hopping.
A convenient technique for determination of reactivity ratios
Authors: Mano Eloisa B. , De Almeida Roberto Riva 
Published: April 2003

AbstractA new technique to determine the reactivity ratios for monomers is described. It is based on vapor‐phase chromatography and can be used for any volatile monomer. A new simplified equation was deduced which permits the direct use of the retention times to obtain the pair r1r2. The method is suggested for use in determination of the molar ratios of the chemical units in the polymer chain, regardless of chemical composition or constitution. The simplicity of this technique allows its use for monomer–polymer systems composed of any number of volatile monomers. The validity of this method was checked by using the pair methyl methacrylate–styrene. This technique is also being applied to the study of kinetics in polymerizations, since it allows the measurements of several samples taken from a single experiment.
Charge‐transfer complexing in polymer mixtures. IV. Acceptor polymers from nitrophthalic acids and their mixtures with donor polymers from aryliminodiethanols
Authors: Sulzberg Theodore , Cotter Robert J. 
Published: April 2003

AbstractA series of electron acceptor polyesters was prepared from 5‐nitroisophthalic, nitroterephthalic, and 4,6‐dinitroisophthalic acids. Those polymers prepared at high molecular weight were tough, soluble, linear materials of well‐defined structure. These materials were mixed with electron‐donor polymers based on aryliminodiethanols where the aryl group was phenyl, p‐anisyl, 2,5‐dimethoxyphenyl, and 3,4,5‐trimethoxyphenyl. The effects of the mixtures on the mechanical, spectral, viscometric, and conductive properties were studied and compared to the component polymers.
Polymerization of monolayers of vinyl and divinyl monomers
Authors: Beredjick N. , Burlant W. J. 
Published: April 2003

AbstractMonolayer balance techniques have been used to study “two‐dimensional” polymerization of monomolecular films of octadecyl methacrylate and a divinyl ester. Polymerizations were initiated with ultraviolet radiation, and reaction rates and properties of the product evaluated from surface pressure–area isotherms. The polymerization rate of the acrylate in argon is linear up to 70% conversion; the product obtained in this way exhibits an isotherm which may reflect the packing and orientation of the starting monolayer. Rate data for the divinyl system—the product of which should be a sheet‐like, two‐dimensional analog of a network system—exhibit no unusual features.
Syntheses and reactions of ferrocene‐containing polymers. III. Cyclopolymerization of 1,1′‐divinylferrocene
Authors: Kunitake Toyoki , Nakashima Toshihide , Aso Chuji 
Published: April 2003

Abstract1,1′‐Divinylferrocene was polymerized with BF3OEt2 and AIBN initiators. Polymers were separated into benzene‐soluble and benzene‐insoluble fractions, the latter probably being crosslinked. The polymers obtained with BF3OEt2 were shown by infrared and NMR spectroscopy to contain both cyclized (70–80%) and uncyclized units, whereas the radical polymer consisted of more than 96% cyclized units. The benzene‐soluble fraction of the cationically obtained polymer softened at temperatures below 150°C, but the insoluble fraction decomposed at 240°C. The radical polymers were stable up to 250–280°C (dec).
Number of crosslinked monomer units per weight‐average primary chain at the gel point in the emulsion polymerization of 1,3‐dienes
Authors: Dannals L. E. 
Published: April 2003

AbstractWithout new assumptions, it is demonstrated that at the gel point in mercaptanregulated, 1,3‐diene emulsion polymerizations, the number of crosslinked monomer units per weight‐average primary chain is larger than one. The divergence of this number from one increases as the nonrandomness of the crosslinked monomer units distribution and the heterogeneity of primary chain size increase. According to the available experimental data, this number ranges from 1.11 to 1.29. Crosslink density values and rate constants of crosslinking to propagation, which were calculated assuming this number to be one, are consequently increased. It is also demonstrated, for postulated systems, that this number may be larger or smaller than one, depending on the type of nonrandomness of the crosslinked monomer units distribution. In either case, the divergence of this number from one also increases as the nonrandomness of the crosslinked monomer units distribution and the heterogeneity of primary chain size increase.
Studies on the polymerization of methyl methacrylate activated by azobisisobutyramidine
Authors: Gupta Satyendra Nath , Nandi Uma Shankar 
Published: April 2003

AbstractKinetic studies on methyl methacrylate polymerization were carried out with watersoluble 2,2′‐azobisisobutyramidine (ABA). The rate of polymerization was proportional to the square root of the initiator concentration in the solvents chloroform, methanol, and dimethyl sulfoxide (DMSO), which confirms the bimolecular nature of the termination reaction. The monomer exponent was unity in chloroform but in methanol and DMSO the rate of polymerization passed through a maximum when plotted against the monmer concentration. This behavior in methanol has been attributed to be due to the enhanced rate of production of radical with increasing proportion of methanol. The rate of decomposition of the ABA has been observed to be faster in methanol than in chloroform. The situation becomes more complicated with DMSO, which was found to reduce the value of δ = (2kt)1/2/kp in methyl methacrylate polymerization. The rate of polymerization was observed to be highly dependent on the nature of the solvent, the rate increasing with increased electrophilicity of the solvent. The dependence of Rp on the solvent has been explained in the light of the stabilization of the transition state due to increased solvation of the basic amidine group of the initiator with the increased electrophilicity of the solvent.
Radiation‐induced postpolymerization of trioxane in the solid state. II. Kinetic study of radiation‐induced postpolymerization of trioxane in dry and high‐vacuum system
Authors: Ishigaki Isao , Ito Akihiko , Iwai Tadashi , Hayashi Koichiro 
Published: April 2003

AbstractA kinetic study of the radiation‐induced postpolymerization of trioxane in the solid state has been made. Trioxane was purified by sublimation through Ag2O and Na–K alloy in vacuo and was both irradiated and polymerized in a super‐dry system under high vacuum. In the present study it was found that the initial rate of polymerization is larger than that reported previously. It is reasonably suggested that the postpolymerization of trioxane consists of two stages, i.e., a very large rate at the first stage and a relatively small one at the second stage. By using the kinetic scheme proposed previously kinetic parameters at the second stage were determined. It was found that trioxane can be postpolymerized even at a temperature below 30°C with good reproducibility and that the overall activation energy of the polymerization was less than 15 kcal/mole. No chain‐transfer reaction seems to occur except at low temperatures. These results have been discussed in comparison with data reported previously.
Phenylated imide–quinoxaline copolymers
Authors: Augl J. M. 
Published: April 2003

AbstractPhenylated, ordered imide–quinoxaline copolymers of high oxidative‐thermal stability were prepared by one‐step solution condensation of aromatic tetraamines with N,N′‐bis(4‐benzilyl)pyromellitimide. Polymerization in m‐cresol leads to high molecular weight polymers that remain soluble. Thermal gravimetric analysis and isothermal decomposition at 400°C shows that these polymers are as stable as polyimides or polyquinoxalines. The polymer decomposition temperatures range between 495 and 550°C, depending upon structure. Also, the rate of isothermal decomposition at 400°C in air showed a strong dependency of weight loss on structure. Tough films were cast from solution.
Polymers containing anthraquinone units: Benzimidazole and benzothiazole polymers
Authors: Kokelenberg Hendrik , Marvel C. S. 
Published: April 2003

AbstractIn an attempt to synthesize soluble polymers, diphenyl 1,5‐anthraquinonedicarboxylate was treated with 3,3′‐dimercaptobenzidine and 3,3′‐diaminobenzidine under various conditions. Although the ester reacted readily, side reactions prevented the formation of high molecular weight compounds. It was thought that at the elevated temperatures required for reaction, the quinone group was involved in a type of Schiff's base formation. The thermal stability of the polymers was evaluated. Model compounds were prepared and their absorption spectra were compared with those of the polymers. It was observed that 1,5‐anthraquinonebibenzimidazole‐2 formed a stable product with acetic acid. Some of the polymers could be solubilized by reduction with sodium dithionite in alkali, but no useful fibers were produced from these solutions.
Polyamides: Decarboxylation and desamination in nylon 6 equilibrium polymer
Authors: Reimschuessel H. K. , Dege G. J. 
Published: April 2003

AbstractRate and extent of both decarboxylation and desamination in the temperature range of 250–290°C were studied on equilibrium polymers obtained by the hydrolytic polymerization of ε‐caprolactam. Mechanisms have been proposed that are characterized by the participation of the equilibrium monomer in the considered decomposition reactions. The mechanisms suggested accommodate both the experimental results of this study and findings of previous investigations as reported in the literature.
Synthesis of homologous monomers and polymers of carbazole, phenothiazine and dibenzazepine
Authors: Gipstein Edward , Hewett William A. , Need Omar U. 
Published: April 2003

AbstractMonomers and polymers of 3‐vinyl‐N‐ethylcarbazole, 3‐vinyl‐N‐methylphenothiazine, 3,7‐divinyl‐N‐methylphenothiazine, N‐acrylylcarbazole, N‐acrylylphenothiazine, and N‐acrylyl‐ and N‐methacrylyldibenzazepine have been synthesized. The synthetic procedures for preparing the monomers and polymers are described.
Importance of the singlet–triplet transition of ethylene in its photopolymerization in the presence of oxygen
Authors: Hagiwara Miyuki , Okamoto Hidemasa , Kagiya Tsukasa , Kagiya Tsutomu 
Published: April 2003

AbstractThe rate of the photopolymerization of ethylene initiated by a mercury are lamp was investigated under a pressure of 400 kg/cm2 at 30 ± 5°C by varying the wavelength of incident light. Ethylene was found to polymerize by ultraviolet light below about 3500 Å. The yield decreased gradually as the wavelength became longer, and no polymer was obtained at wavelength greater than 3900 Å. The addition of a small amounr (<100 ppm) of oxygen promoted the polymerization. Ultraviolet absorption spectat measured for the mixture of ethylene and a small amount of oxygen displayed several absorption peaks in the region 2700–3500 Å. The absorption began at about 3680 Å and became stronger with the concentration of oxygen. The average separation between the peaks was about 1000 cm−1. The spectra were also measured for oxygen containing a small amount of ethylene. Similar absorption peaks with those described above were observed. On the basis of these results, it was pointed out that an excited triplet ethylene is formed under the irradiation of light due to a perturbing effect of oxygen contained in ethylene monomer and the reaction between the excited ethylene and oxygen is important in initiating the polymerization.
Stereospecific polymerization of isobutyl vinyl ether by AIR3–VCl3·LiCl catalyst. II. Effects of polymerization conditions on polymerization
Authors: Joh Yasuhi , Yuki Heimei , Murahashi Shunsuke 
Published: April 2003

AbstractThe effect of polymerization conditions such as aging time of the catalyst, polymerization temperature, polymerization time, monomer concentration, and catalyst concentration on the polymerization of isobutyl vinyl ether was intensively studied by using the VCI3·LiCl–Al(i‐Bu)3 system at an Al(i‐Bu)/VCl3·LiCl ratio of 6 at which the cationic polymerization by VCl3·LiCl is sufficiently depressed. About 10 min aging of the catalyst in the presence of monomer yields a fairly stable catalytie system. The optimum polymerization temperature is around 30°C. The conversion increased with increasing monomer concentration, whereas the stereospecificity of polymerization decreased. Unexpectedly, the conversion decreased as total catalyst concentration increased. This phenomenon is explained by considering the deactivation of catalytic sites by the excess of Al(i‐Bu)3. A reasonable mechanism from kinetic considerations is that two molecules of Al(i‐Bu)3 deactivate the catalytic site in an equilibrium reaction. This deactivation is understandable by considering that the coordination of two molecules of Al(i‐Bu)3 will occupy all the coordination positions of vanadium, so that there is no room for coordination of monomer coming to the catalytic site.
Effects of mercaptides on anionic polymerization. II. Polymerization of acrylonitrile initiated by mercaptides
Authors: Hirahara Takuji , Minoura Yuji 
Published: April 2003

AbstractThe polymerization of acrylonitrile by the several alkali metal mercaptides was investigated. The initiation reaction was found spectroscopically and by the sodium fusion method to proceed in a Michael‐like form similar to a cyanoethylation reaction. From the results of the copolymerization of acrylonitrile and methyl methacrylate by the mercaptides, it was found that the mercaptides behaved as the anionic initiators. The effects of the counterions on the rate of polymerization were found to increase with increasing the electropositivites in the order of Li < Na < K. A negative overall activation energy was obtained, −2.2 kcal/mole, in the temperature region of −30°C to +20°C. The catalytic reactivities of the mercaptides were smaller than those of the corresponding oxygen analogs, except in the case of the phenyl substituent. Only in the case of the phenyl substituent, thiophenoxide was found to be much more effective than phenoxide, phenyl‐SNa ≫ phenyl‐ONa. The catalytic reactivities of the various sodium mercaptides were also determined to follow not only the basicities of the nucleophiles, but also the polarizabilities as follows: tert‐butyl‐SNa ≈ n‐dodecyl‐SNa > phenyl‐SNa > n‐octyl‐SNa > isopropyl‐SNa > n‐propyl‐SNa > ethyl‐SNa. The enhanced reactivity of thiphenoxide in spite of the low pKa value was attributed to the higher polarizability based on the low α effect.
Copolymerization of styrene and butadiene in emulsion. II. Relative rates of crosslinking and propagation
Authors: Burnett G. M. , Cameron G. G. , Thorat P. L. 
Published: April 2003

AbstractFor the styrene–butadiene emulsion copolymerization (71 parts butadiene:29 parts styrene) the ratio of the rate coefficients for crosslinking, kx, and propagation, kp, have been determined at 5, 15, and 25°C by using an adaption of the method of Morton and co‐workers. These ratios yield a value of 4.85 kcal/mole for the difference in activation energy between crosslinking and propagation, Ex − Ep. Since the relative frequency of crosslinking and propagation depends upon the copolymer composition, and hence upon the free monomer ratio and the temperature, the range of application of these data is more limited than in a simple homopolymerization.
Thermal degradation of polymers with phenylene units in the chain. IV. Aromatic polyamides and polyimides
Authors: Ehlers G. F. L. , Fisch K. R. , Powell W. R. 
Published: April 2003

AbstractThe breakdown mechanism of an aromatic polyamide and four polyimides has been studied under vacuum in the temperature range of 375–620°C, by using techniques described earlier, involving collection and analysis of volatile products as well as analyses of residues at different temperatures. The decomposition of the polyamide up to 375°C yielded predominantly carbon dioxide, while between 375 and 450°C about equal amounts of carbon dioxide and carbon monoxide formed. Hydrogen is the major product between 450 and 550°C, along with hydrogen cyanide, methane, and carbon monoxide. The major reaction at the lower temperatures seems to be the cleavage of the linkage between the carbonyl group and the ring, with subsequent formation of a carbodiimide linkage via isocyanate intermediates, and liberation of carbon dioxide. Alternatively, cleavage between the carboxyl and the NH‐group leads to the formation of carbon monoxide. Carbon dioxide and carbon monoxide are also the major volatile decomposition products of the polyimides at the lower temperatures. The primary cleavage reaction is believed to be the rupture of the imide ring between a carbonyl and nitrogen, with subsequent formation of isocyanate groups. The latter react with each other to form carbodiimide linkages and carbon dioxide, while the remaining benzoyl radical is the source for carbon monoxide.