bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of macroradical reactivity by an electron paramagnetic resonance method
Authors: Bresler S. E. , Kazbekov E. N. , Saminskiĭ E. M. 
Published: April 2003

AbstractThe formation of macroradicals in the mechanical degradation of polymers gives the means for the direct kinetic determination of macroradical reactivity (reaction of the macroradicals with each other and with various low molecular substances). The free radical concentration was determined by means of EPR spectroscopy. With the aid of this method a study was made of the characteristic reactions such as removal of a hydrogen atom, addition, etc.
Synthesis and polymerization of polyacrylic esters
Authors: Kefeli T. Ya. , Korolev G. V. , Filippovskaya Yu. M. 
Published: April 2003

AbstractThe method of telomerization has been employed in the synthesis of the telomer homologs of polyacrylate esters with successively increasing degrees of polymerization (n) and of telomers differing in the nature of the polyester chain. Compounds have been synthesized of the general formula
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where R and R1are alkyl or aryl radicals and n = 2, 4, 8, and 20. With changes in (n) from 2 to 20 the structural viscosity of the polyacrylate esters increased from 150 to 8000 centistokes (at 20°), the specific gravity from 1.213 to 1.308, and nD20 from 1.515 to 1.5479. The presence of double bonds in the molecules of the polyacrylate esters synthesixed made it possible to carry out their polymerization (hardening) in the presence of radical chain initiators with the formation of glassy or elastic, insoluble, nonmelting polymers of sufficient thermal stability and endowed with a number of valuable properties so as to be of considerable practical potentiality. The changes in physical properties of the reaction system (gelation, gradual increase in density and finally the formation of a glass structure) in the course of the polymerization beginning from the very early stages (the gelation point is reached at 5–10% conversion) are responsible for a number of specificities in the kinetics of the hardening of polyacrylate esters. Owing to this we undertook a detailed investigation of the polymerization kinetics under widely varying conditions. Polymerization in bulk takes place autocatalytically, since with increasing degree of structuration in the course of polymerization the rate of diffusion of free radical diminished, leading to a decrease in rate of chain termination. The rate of reaction begins to diminish markedly only at large extents of polymerization. A study has been made of the effect of diluting the reaction mixture with an inert solvent, of the initiation rate, nature of the initiating agent, temperature, chemical structure of the initial polyacrylate ester, as well as of the addition of inhibiting agents on the polymerization kinetics. The results obtained have been discussed from the standpoint of the capacity of the system for structuration under the various conditions of reaction. The heats of hardening of the polyacrylate esters with successively increasing distance between their values have been discussed with respect to the reaction mechanism.
Preparation of new types of linear polymers by the polyrecombination reaction
Authors: Korshak V. V. , Sosin S. L. , Alekseeva V. P. 
Published: April 2003

AbstractIn an extension of previously reported studies of the use of the polyrecombination reaction to synthesize high molecular weight compounds, it has been shown for the first time that this method yields linear polymers without any significant formation of threedimensional structures. Such polymers may be synthesized from compounds containing a methylene group in the α‐position to the benzene ring, carboxyalkyl or carboxyphenyl groups. On treatment of diphenylmethane with tert‐butyl peroxide, a linear polymer of molecular weight 10,000‐900,000 (depending on the quantity of peroxide used) was obtained. Linear polymers in the form of benzene‐soluble powders were also obtained from benzyl benzoate (molecular weight 400,000), methyl phenylacetate, etc. The composition and structure of the polymers obtained were confirmed by chemical analysis and infrared spectroscopy. The relation between the molecular weight of the polymer and the amount of peroxide consumed in the reaction was also established. If groups capable of serving as branching centers in the polymer (e.g., methyl groups in ditolylmethane) are present in the starting compounds, three‐dimensional products are formed along with the linear polymers.
Polymeric organotin compounds
Authors: Shostakovskiĭ M. F. , Kalinina S. P. , Kotrelev V. N. , Kochkin D. A. , Kuznetsova G. I. , Laine L. V. , Borisova A. I. , Borisenko V. V. 
Published: April 2003

AbstractOrganotin monomers and polymers are becoming of increasing importance. Of especial theoretical and practical interest are polymers of organotin materials. In the present report results are described of studies carried out in the Laboratory of Vinyl Compounds of the Institute of Organic Chemistry of the Academy of Sciences, USSR and in the Plastics Institute of the State Committee on Chemistry of the Council of Ministers, USSR. The syntheses of a number of organotin polymers are reported, in particular, of the organotin polymethyl methacrylates from trialkyl (or aryl) stannyl methacrylates R3SnOCO(CH3)CH2 and dialkyl (or aryl) stannylene dimethacrylates R2Sn[OCOC(CH3)CH2]2 and copolymers based on these. The high molecular compounds obtained by polymerization of the organotin esters are a new class of vinyl polymers with the structure:
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Organotin esters copolymerize with various unsaturated monomers such as methyl methacrylate, styrene, acrylonitrile, cyclopentadiene, etc. The copolymers are mechanically strong, transparent materials. They represent considerable barriers to the passage of x‐rays. The organotin esters R3SnOCOC(CH3)CH2 and R2Sn[OCOC(CH3)CH2]2 containing the alkyl radicals amyl, hexyl and higher groups polymerize at room temperature in the absence of catalysts to form soft and elastic polymeric materials. In the report a number of properties of another class of organotin polymers, namely, dialkyl (or aryl) stannones (R2SnO)n are discussed. It is suggested that they are high molecular compounds. Their x‐ray diagrams and the results of other physicochemical analyses are examined. A study of their Debye x‐ray diagrams showed that they have a regularly oriented structure. They are highly reactive and are sources for the preparation of new organotin compounds. Some of their physicochemical properties are described.
On the mechanism of ionic polymerization
Authors: Veselý K. 
Published: April 2003

AbstractThis lecture is devoted mainly to individual elementary reactions, especially those of chain growth taking place on a pair of ions, and termination in ionic polymerization. Two mechanisms of chain growth are possible and are known to occur: first, a gradual chain growth taking place at the ion pair (as is known in the case of “living” polymers), second, chain growth taking place at free ions. The velocity of chain growth is controlled by a number of factors amongst which may be cited the following (a) The type of the chemical bond in the monomer which undergoes cleavage during polymerization. In this respect the author correlates results of kinetic measurements (partly his own and partly other authors' data) relating to the bonds >CC< (in isobutylene, styrene), >CO (in formaldehyde), and (in octamethylcyclotetrasiloxane, OTS). (b) The size and type of ions forming the ion‐pair. Here different anions are compared for their effects on the cationic polymerization of isobutylene and, similarly, different cations are compared for their effects on the anionic polymerization of OTS. (c) The ability of monomer to form complexes with the ion‐pair at which growth occurs. During the anionic polymerization of OTS the free orbital of the Si atom of the monomer is directly engaged in the dissociation of the terminal ion‐pair . The role of the aromatic nucleus in the polymerization of styrene falls within the same category. More detailed data on the dissociation of ion pairs have been obtained by the study of electrical conductivities of catalyst‐cocatalyst systems on the one hand and of systems involving monomer on the other. The study of electrical conductivities in the presence of a monomer was carried out in the anionic polymerization of OTS which is characterized by relatively low rates of polymerization. Here it was possible to prove the active part played by the monomer in the dissociation of the ion‐pair at which chain growth takes place. The termination reaction on the other hand is also influenced by a number of factors. Among the most important factors is the acidity (or basicity) of the growing ion which decides whether the actual step is one of transfer or termination. By way of an example one may draw the attention to the difference in behaviour of water on the polymerization of the CC bond on one hand, that of the CO bond on the other. The reactivity of the very strong cations (of anions ) is sufficient for even relatively strong bases (or acids) to add irreversibly. As an example one may show the action of various bases in the cationic polymerization of isobutylene and that of acids in the anionic polymerization of OTS. In conclusion, absolute rates of the individual elementary reactions and the new possibilities opened by the study of electrical conductivities of monomer‐containing systems are discussed.
The mechanism of polymerization of ε‐aminocaprolactam catalyzed by phosphoric acid
Authors: Geleji F. , Szafner A. , Holly Z. , Szollar L. 
Published: April 2003

AbstractThe polymerization of caprolactam in the presence of water has been studied by several authors. In the papers of Wiloth, Hermans, and Mathes, the attention was essentially devoted to the temporary production of aminocaproic acid, which polymerizes progressively by a condensation mechanism. It was demonstrated that the catalyst (water, aminocaproic acid, hexamethylenediamine adipate) assures the polymerizability of the system at the condensation temperature. In order to verify the data of the literature concerning some resistance towards oxygen when prepared in the presence of phosphoric acid, we have used in our studies some phosphoric acid as a catalyst for the polymerization of caprolactam. However, we have found that the oxidation of caprolactam was lower in the presence of an acid than in its absence. It was shown that the higher sensitivity was due to the formation of free radicals by interaction of phosphoric acid with caprolactam, which reacts rapidly with oxygen. The oxidation is slowed down more effectively by inhibitors of polymerization, which react more easily with free radicals than the oxygen. We follow our studies on the basis of these data. It is known from the literature that phosphoric acid is a very effective polymerization catalyst as well in the presence of water as in that of anhydrous medium. Considering that phosphoric acid exerts during the polymerization not only a catalytic effect but, first of all, a chain‐breaking process, we have used optimal quantities of phosphoric acid which lead to the best end products. The best adapted molecular weights are obtained in the presence of 1/100–1/200 mole phosphoric acid for 1 mole caprolactam. With such quantities of phosphoric acid in the presence or in the absence of water, the polymerization proceeds rapidly. The rate of polymerization is inversely proportional to the square root of the catalyst concentration. By decreasing the amount of catalyst to 1/400 or 1/200 mole per mole of caprolactam, the water content which is present besides the catalyst becomes more important and different rates of polymerization are observed in function of the phosphoric acid concentration. At the polymerization temperature, the phosphoric acid tends to dehydrate into pyrophosphoric acid; this transformation enhances the production of the most reactive free radicals. These free radicals increase the rate of ring opening of caprolactam more strongly than in the presence of water. In agreement with our opinion, phosphoric acid catalyzes not only the ring opening, but increases also the chain propagation reaction.
The effect of aging of polychloroprene on its crystallization
Authors: Kössler I. , Švob L. 
Published: April 2003

AbstractSamples of polychloroprene (Svitpren K) were submitted to aging in air at elevated temperatures (65, 80, 90 and 100°C.). The kinetics of the crystallization process were then followed on the samples. The degree of crystallization was determined by x‐ray diffraction. The maximum degree of crystallization was 34% with a fresh sample. With increasing degree of aging, this value decreases markedly even though the rate of crystallization does not change appreciably. The activation energy E of the chemical reaction was found from curves giving the dependence of the limiting degree of crystallization on the period of heating the sample at various temperatures to be E = 8.5 kcal./mole. This value was close to that determined directly from the splitting off of HCl, E = 9.2 kcal./mole. Thus the splitting off of HCl is the main factor in decreasing the limiting value of the crystallization. This process does not have any effect on the rate of crystallization since the segments on which the splitting off of HCl occurred do not decrease the mutual mobility of the chains. They cannot, however, participate in the formation of crystallites. We attribute the small lowering of this rate of crystallization to crosslinking of the polymer molecules but which has in the first phase of the aging only a secondary effect on the process of crystallization. The crystallization isotherms of all the samples thus satisfy the Avrami relation with a value of the constant n = 2. The rate of nucleation is large in comparison with the rate of growth of centers. Secondary crystallization was not observed.
The stereoregulating effects of aldehydes on the free radical polymerization of vinyl chloride
Authors: Rosen Irving , Burleigh P. H. , Gillespie J. F. 
Published: April 2003

AbstractThe discovery has been made that when vinyl chloride is polymerized in certain aldehydes, a highly crystalline polyvinyl chloride is obtained. In butyraldehyde, low yields of a range of low molecular weight polymers are produced. Elemental analyses showed that they may be characterized by the formula:
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where n = 6‐26. Support for this structure and molecular weight range was obtained from infrared and x‐ray examinations of the polymers. The polymers are highly crystalline, as demonstrated by the x‐ray and infrared results, and appear to have a syndiotactic structure. Variation of the polymerization temperature produced no measurable effect on the polymer stereoregularity. The ability of substituted aliphatic aldehydes to produce stereoregular PVC has shown a dependence on the electronegativity of the substituent in the aldehyde. Aliphatic aldehydes with an electron‐releasing α‐methyl group appear to give a more highly crystalline PVC. Aliphatic aldehydes with electron‐withdrawing chlorine and oxygen atoms gives less crystalline PVC than do the corresponding α‐methyl aldehydes. The dependence of the results upon polar effects suggests that the stereoregulating mechanism of the aldehydes involves association between the aldehyde, as a donor molecule, and the free propagating species, as the acceptor radical.
The viscoelastic behavior of oriented polyvinyl alcohol fibers at large strains
Authors: Laible Roy C. , Morgan Henry M. 
Published: April 2003

AbstractThe viscoelastic spectra of oriented polyvinyl alcohol fibers have been determined at large strains (2, 5, and 8%). Stress relaxation data were obtained from constant strain rate experiments conducted at testing speeds from 20 to 2,000,000 %/min. and have been used to calculate viscoelastic parameters, E, E0 and tan δ. The heights of the relaxation spectra were found to increase with increasing rate of test, up to the maximum strain rates possible before critical velocity failure occurs.
Über die polymerisationsgradverteilung bei der polykondensation. Ein versuch zur deutung der tungschen gleichung
Authors: Sippel A. , Heim E. 
Published: April 2003

AbstractIn 1956 L. H. Tung has given a quite empirical and formal mathematical relationaship, by which—appropriate plotting of data provided—it is possible to represent the distribution of DP values, as obtained by a completed polymerization (polycondensation or polyaddition), by means of a straight line. In the course of the present publication it is shown that the authors—starting from a quite different problem—have found a relationship that proves (after an insignificant simplification and by suitable interchange of symbols) to be identical with Tung's equation. According to some special ideas about the chemism, the method of deducing this equation enables the authors to interpret Tung's equations in terms of kinetics. The basic equations obtained are

These show that the reaction rate is merely proporional to the number N of monomers and to the time t. The chain lengths of the macromolecules are suggested to be only an appropriate measure for the time elapsed from the beginning of their formation. Interpreting Tung's equation kinetically it is possible to get information about the distribution of DP values that is to be expected at a given temperature. With regard to theoretical considerations one expects the integral number 2 to be used for the exponent b in the modified equation originally given by Tung:

This value is related to the fact that the chain growth takes place in two directions because of the bifunctionality of the monomers. Therefore, the termination of the reaction will also take place in two steps. The correctness of these suggestions is confirmed by the fact that (for all known fractionations of polycondensation products) the exponent b proves to be nearly 2. Using the value b = 2 the whole chain lengths distribution of normal polycondensation products can be easily calculated by means of one single number or weight‐average value of the DP as determined with an unfractionated sample.
The electrolytic reduction and sodium reduction‐polymerization of acrylonitrile
Authors: Murphy Sister Mary , Carangelo Maria G. , Benedicta Ginaine M. , Clare Markham M. 
Published: April 2003

AbstractThe reduction of acrylonitrile at mercury electrodes has been studied both polarographically and coulometrically at controlled potential. The half‐wave potential is about 1.6 v. versus a mercury pool both for pure acrylonitrile and for acrylonitrile in dimethylformamide, in the presence and absence of water. As long as water is present the diffusion current is directely proportional to the concentration of acrylonitrile, at least up to 0.2 mg./ml. In the absence of water, reduction of acrylonitrile in dimethylformamide at this potential leads to condensation of reactions initiated by the carbanion. The diffusion current is no longer proportional to the concentration. Comparison of electrolytic‐ and sodium‐reduction products of acrylonitrile gives information about the mechanisms of these reductions and the role of water in the polarographic analysis. A new yellow sodium‐reduction polymer of acrylonitrile is described, and data on the ultraviolet and infrared spectra are presented.
The adsorption of polydimethylsiloxanes from solution
Authors: Perkel Robert , Ullman Robert 
Published: April 2003

AbstractThe adsorption of polydimethyl siloxane polymers from solution onto polar surfaces has been studied. The amount of polymer adsorbed is unusually sensitive to the presence of moisture, which strongly inhibits adsorption. The adsorption increases with the molecular weight of the polymer and depends on the solvent because of the polymer‐surface, solvent‐surface, and polymer‐solvent interactions. The dependence of adsorption on temperature was studied, as was adsorption‐desorption equilibrium. A few experiments were carried out on the adsorption of polypentamethyldisiloxane methacrylate, a material which, in its adsorption behavior, is intermediate between polydimethyl siloxane and vinyl polymers with polar substitutents. The relationship of the results obtained here to various models of polymer chain configuration at the liquid‐solid interface is considered.
Rubber elasticity and chain configuration
Authors: Tobolsky A. V. , Carlson D. W. , Indictor N. 
Published: April 2003

AbstractVarious theories accounting for the existence of a front factor in the equation of state for rubber elasticity are reviwed. It is shown that a front factor which may be different from unity exists whether or not intramolecular energy effects are present. A unified theory is presented which is applicable both to Gaussian chains and to chains with intramolecular folding energy. Stress‐temperature measurements were used to obtain values of the intramolecular folding energy ϵ′ for numerous crosslinked polyacrylates and polymethacrylates. The values of ϵ′ for almost all of the polyacrylates were found to be approximately zero; the values of ϵ′ for the polymethacrylates varied generally between ‐350 and ‐700 cal./mole, indicating a preference for folded configurations. The front factors were also determined for these crosslinked polymers at 60°C. The front factor appears relatively independent of the degree of crosslinking. There appears to be a general trend to smaller front factors as the size of the alkyl chain increases in both series. An interpretation in terms of network interpenetration is given in the text. The variation of ϵ′ with copolymer composition has been determined for a series of butyl acrylate‐butyl methacrylate copolymers. The value of ϵ′ for isotactic amorphous poly(1‐pentene) was also measured and found to be zero. Finally, the effect of diluent on the front factor is discussed for the case where diluent is present during the crosslinking process and for the case where it is added after crosslinking.
The dielectric properties of polyelectrolyte solutions
Authors: Johnson G. A. , Neale S. M. 
Published: April 2003

AbstractMeasurements of the dielectric constants and dielectric loss factors of aqueous solutions of potassium chondroitin sulfate, poly‐L‐lysine hydrobromide, sodium ribonucleate, sodium desoxyribonucleate, and two polymetaphosphates, Calgon glass and Maddrell salt, are presented. The data are analyzed by the Cole‐Cole are method1 and relaxation times are calculated by the method of Zaromb.2 Except in the case of sodium ribonucleate the solutions are shown to behave as linear polyelectrolytes and the data are shown to fit the ionic model proposed by O'Konski.3 Sodium ribonucleate does not show the characteristics of a linear polyelectrolyte but appears to behave more like a protein in solution.
Determination of molecular weight distribution in polyvinyl acetate by selective adsorption technique
Authors: Kangle P. J. , Pacsu Eugene 
Published: April 2003

AbstractThe present work deals with the molecular weight distribution in polyvinyl acetate, a synthetic polymer, determined by the technique of fractionation by selective adsorption onto activated carbon. The different variables in the process of selective adsorption of smaller molecules are studied in detail. The critical factors influencing the selectivity of adsorption are adsorbent to polymer ratio and initial concentration of polymer in solution. Sharp fractions are obtained by the technique of elution of adsorbed polymer from the adsorbent with a suitable solvent. The adsorption of polymer from the solution phase onto adsorbent depends on the polymer‐solvent system. The viscosity behavior of PVAc at high dilutions is studied, and it is suggested, that the extension and disentanglement of polymer chains at high dilutions depend upon the solvent used.