bluuebunny/crossref_metadata_2025 huggingface dataset:
Interchain exchange reactions in radical polymerization
Authors: Pyrkov L. M. , Frenkel S. Ya.
Published: April 2003

Interchain exchange reactions with the formation of “hybrid” polymers take place in mixed solutions of two polymers or in solutions of polymers dissolved in “foreign” monomers, in the presence of free radical initiators. A number of methods, namely, turbidimetric titration, ultraviolet spectroscopy, refractometry, and pycnometry were used to identify and analyze the hybride polymers. A qualitative method for determining the “hybridity” of polymers was developed. This consisted in determining the optical and mechanical (relaxation) properties of polymer films obtained from various solvents (poor solvents for one and good solvents for the other type of block or branch of the hybrid polymer). For the quantitative investigation of systems containing the hybrid polymers a new method employing an ultracentrifuge has been developed. This is a modification of Meselson's method (equilibrium centrifugation in a concentration gradient) and consists in centrifuging a mixture of two homopolymers and their hybrid polymer in a mixture of two solvents of which the density has been so chosen that the homopolymers give the Boltzmann distribution at the bottom and at the meniscus of the cell. The hybrid polymer accumulates in a band in the central part. Theoretically the method allows one to determine simultaneously the molecular weight distribution of all three polymers and the composition of the “hybrid” polymer. The present experiments are important in throwing light on the secondary reactions taking place in radical homopolymerization and leading to unusual multimodal or “tailed” molecular weight distributions.
Polymerization and grafting processes on freshly formed surfaces
Authors: Kargin V. A. , Platé N. A.
Published: April 2003

The intensive mechanical dispersion of a number of solid crystalline and amorphous inorganic substances (metals, oxides, and salts) in vinyl monomers was used for polymerizing the latters under simple conditions. The reaction was induced by free radicals or active ions arising on the newly formed surface of the dispersing inorganic substances. Depending upon the nature of the active surface, such polymerization reactions may lead to grafting of the resultant polymer onto the solid surface of the dispersing substances.
Synthesis of cis and trans polymers of dienes on oxide catalysts and investigation of their structure and properties
Authors: Tinyakova E. N. , Dolgoplosk B. A. , Zhuravleva T. G. , Kovalevskaya R. N. , Kuren'Gina T. N.
Published: April 2003

Crystalline 1,4‐trans polymers of butadiene and isoprene of regular structure are formed in polymerization of dienes in a chromia catalyst (chromium oxide on aluminum silicate). 1,4‐trans‐Polybutadiene with a specific gravity of 1.015 has crystalline modifications melting at 75 and 135°C. The 1,4‐trans‐polyisoprene resembles natural gutta‐percha. When α‐butylene undergoes polymerization on the same catalyst, a crystalline polymer is formed of specific weight 0,96 and melting point ca. 140°C. Any disturbance of the 1,4‐trans‐structure by copolymerization of butadiene or isoprene with other compounds leads to a loss of capacity for crystallization and to transition to the high elastic state. The butadiene‐isoprene copolymer contains about 55% butadiene links while preserving the 1,4‐trans structure of the chain and has a glass temperature of ca. −90°C., coinciding with the value calculated on the basis of a linear relation between the copolymer composition and the glass temperature. By copolymerization ethylene units could be incorporated in the trans‐polyisoprene chain to the extent of ca. 40 mole‐%. The polymer formed has a glass temperature of −76°C., as compared with −71°C., for 1,4‐polyisoprene. Polymerization of butadiene induced by the cobalt oxide‐diethyl‐aluminum halides proceeds at a high rate, even at 0°C. The polybutadiene formed contains predominantly links cis‐1,4 (about 85%) and only a small quantity (5–8%) of 1,2 links. Owing to the high content of 1,4 links the polymer has a glass temperature as low as −115°C. Unlike organometallic‐titanium tetrachloride systems, interaction between cobalt oxides and organoaluminum compounds in the temperature range 0–80°C. is not accompanied by formation of gaseous hydrocarbon products.
The synthesis and properties of crystalline polymers of the type of poly‐p‐xylenes and polyphenylene methyl derivatives
Authors: Vansheĭdt A. A. , Mel'Nikova E. P. , Krakovyak M. G. , Kukhareva L. V. , Gladkovskiĭ G. A.
Published: April 2003

For the purpose of obtaining polymeric hydrocarbons of enhanced thermostability, linear polymers of regular structure of the type (CH2ArCH2)n and (ArCH2)a with aromatic units in the chain were synthesized. Polymers of the first type were obtained by reaction of metallic sodium with the dichloromethyl derivatives of benzene, m,‐ and p‐xylenes, diphenylmethane, diphenyl and naphthalene in dioxane medium at 20–25°C. The m‐xylene derivative had a CH2Cl group in the m‐position and the others, dichlorides in the p‐ or p,p′‐positions. The polymers were precipitated from the solutions on forming and after removal of excess sodium with the aid of methanol and elimination of the low molecular impurities they appeared as colorless powders of the composition of hydrocarbons, at times containing chlorine. X‐ray analysis of the polymers revealed the presence of a crystalline structure the degree of which varied, depending upon the structure. The polymers differed greatly in solubility and melting points. Thus naphthalene and diphenyl derivatives, evidently being crosslinked three‐dimensional polymers, did not dissolve even in boilling α‐bromonaphthalene and decomposed above 300° and 550° without melting, while derivatives of other hydrocarbons dissolved in bromonaphthlene, melted, and probably were linear polymers of low molecular weight. The m‐xylene derivative was distinguished by low crystallinity, low melting point (130–135°C.) and easily dissolved in chloroform even in the cold. Diphenylmethane derivatives with a more clearly expressed crystallinity melted at 250–255°C. and began to dissolve in α‐bromonaphthaline only at 130°C. p‐Xylene derivatives, like poly‐p‐xylylene, were highly crystalline and melted at 350°, but began to dissolve in bromonaphthalene only at 235°. The molecular weight of the soluble polymers could be determined (according to Rast's method) only for the soluble m‐xylene derivative, which, depending upon the conditions of formation, varied from 1850 to 4000. Polymers of the second type were obtained by polycondensation of aromatic hydrocarbons with paraform and also with the dichloro‐, dioxy‐, and diacetoxymethyl derivatives of aromatic hydrocarbons in boiling glacial acetic acid containing sulfuric acid. In this way starting from p‐xylene and durene one could obtain high‐melting crystalline polymers with melting points above 250 and 320°, dissolving only in high boiling solvents. Condensation of durene with dichloromethyl derivatives of p‐ and m‐xylene as well as with p‐xylylene chloride led to the formation of high melting polymers of the type (ArCH2Ar′CH2)n containing two different aromatic units in the chain.
Cyclic polymerization and copolymerization of divinyl acetals
Authors: Matsoyan S. G.
Published: April 2003

Cyclic polymerization constitutes an intramolecular closure of isolated dienes into five‐ or six‐membered rings with concurrent intermolecular growth of the chain. We have synthesized for the first time divinyl acetals and have investigated their capacity for cyclic polymerization. A method had been developed for the synthesis of divinyl‐acetals through interaction of aldehydes with ethylene chlorodihydrin and the subsequent dehydrochlorination of β,β′‐dichlorodiethylacetals. The structure of the divinyl‐acetal monomers was proved, in particular, by hydrolysis and hydrogenation. It has been shown that, in the presence of initiators of radical polymerization, divinylacetals polymerize only by means of the cyclic mechanism, with the formation of acetal derivative of polyvinyl alcohol, i.e., polyvinylacetals. The name “polyvinylacetal” based on the name of the monomer should be changed to “polydivinylacetal”
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Where R = H, CH3, C3H7, iso‐C3H7, iso‐C4H9 and C6H5. Polyvinylacetals have been obtained with an extent of acetylation of 100%. Until recently the possibility of cyclic copolymerization was not known. We have investigated this reaction on the examples of the copolymerization of divinylacetals with vinyl and diene monomers:
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where R = H, CH3, and C3H7 and X = OCOCH3, CN, and C6H5.The possibility of cyclic cyclopolymerization has been demonstrated by copolymerization of divinylformal and divinylethanal. All polymers obtained by us are white powders or rubberlike thermoplasts, easily soluble in most organic solvents and possessing high adhesive properties. They do not add hydrogen or bromine, indicating the absence of double bonds. The structure of the polyvinylacetals obtained on cyclopolymerization of divinylacetals was demonstrated by means of hydrolysis. As was to be expectd, polyvinyl alcohol was formed, of which in turn the glycol structure was proved by its oxidation to oxalic acid. Hence two vinyl groups of the divinylacetals during intrainter molecular polymerization react by the “head to tail” mechanism to form polyvinylacetals with six‐membered cyclic structures.
Polymerization of vinylcarbazole in the presence of butyllithium and titanium tetrachloride
Authors: Solomon O. F. , Dimonie M. , Ambrozh K. , Tomesku M.
Published: April 2003

The polymerization of large cyclic vinyl compounds is of considerable interest in the interpretation of the mechanism of action of complex organometallic catalysts. Numerous vinyl compounds have been investigated up to now but no study has been made of compounds containing large rings. Studies on the isotactic polymerization of vinylcarbazole have brought to light very important facts permitting of a number of inferences as to the mechanism of isotactic polymerization. Despite the large molecular volume of vinylcarbazole and the steric hindrances that should be expected due to this, a study of the polymerization kinetics has revealed reaction rates similar to those observed in the polymerization of other monomers. The study of the polymerization of vinylcarbazole and of other monomers showed that the butyllithium‐titanium chloride catalyst belongs to the class of organometallic complexes that act either by a stepwise or ionic mechanism. The specific features of complex organometallic catalysts in the polymerization of vinylcarbazole are evidently associated with preliminary activation of the active centers during which activation of the monomer also takes place. The formation of polymers with an isotactic microstructure is due to one of the possible mechanism of the catalysis, namely, to nonstepwise action. In the polymerization of vinylcarbazole in the presence of organolithium compounds and titanium tetrachloride the microstructure of the resultant polymer and the rate of polymerization depend upon the formation of other than primary complex compounds. The microstructure of isotactic polyvinylcarbazole shows a particular shape of spherulites, depending upon the nature of the catalyst.
Cooperative processes in the polycondensation of biopolymers
Authors: Vol'Kenshteĭn M. V.
Published: April 2003

The main features of the polycondensation of biopolymers—nucleic acids and proteins—can be summarized in the following. The reactions are accomplished with the participation of enzymes and take place on some kind of template. Many facts show that the template for deoxyribonucleic acid (DNA) is a nucleoproteinic complex containing DNA; and for protein, a complex containing DNA and RNA (ribonucleic acid). The polycondensation process on a template is a cooperative phenomenon essentially determined by the near‐neighbor interactions of monomers linked by hydrogen bonds to the polymer chains acting as the template. From this a simple model and a statistical theory of the reduplication synthesis of DNA have been developed. The reaction has been shown to start at a certain critical concentration of the monomers in solution, the process being characterized by a specific thermodynamic phase transition.

The following factors have been taken into account: the hydrogen bond energy, the energy of nucleotide polycondensation liberated in a sequence of coupled reactions, the influence of the solvent (water) and the flexibility of the free polymer chain. The calculations are based on the Ising method used in the theory of ferromagnetism. The transition during the reduplication synthesis is the sharper the greater the length of the template chain. The same treatment can be applied to the statistical‐thermodynamics analysis of protein biosynthesis in the form of α‐helices (after Pauling and Corey). Polycondensation of amino acids also proceeds by a cooperative mechanism. In this case not only the hydrogen bonds between the amino acids and the template have to be taken into account, but also the intramolecular hydrogen bonds of the resultant α‐helix. Also in the case of amino acid polycondensation on a template a sharp transition takes place at a definite monomer concentration (or at a definite temperature). The kinetics of polycondensation of biopolymers can be treated analogously if we take into account the cooperative character of the process. The corresponding differential equations are nonlinear, but their approximate solution makes it possible to characterize the main features of the process. The above simple models can be generalized to include the successive biosynthesis of nucleic acids and proteins as a united process. The same conceptions may be employed in the theory of heterogeneous catalysis.
The effect of chemical structure on the ability of unsaturated organometallic compounds to undergo polymerization
Authors: Koton M. M. , Kiseleva T. M. , Florinskiĭ F. S.
Published: April 2003

The synthesis of metal‐containing polymers is of considerable theoretical and practical interest (organotin rubbers, etc.). We investigated the polymerization and copolymerization capacities of various allyl and vinyl derivatives of tin and lead, of tin, lead and mercury methacrylates and of a number of metal‐containing styrenes. The allyl derivatives of tin and lead and the vinyl derivatives of tin do not polymerize under conditions of radical polymerization and have an inhibiting effect on polymerization of vinyl monomers (styrene, methyl methacrylate). The inhibiting effect increases with the number of allyl and vinyl groups in the organometal molecule, the allyl compounds of tin being more effective than the corresponding vinyl derivatives. The inhibiting action on the polymerization of vinyl monomers of the compounds decreases in the order: tetraallyltin > tetravinyltin > allyltrimethyltin > diallyldiphenyltin > allyltriphenyltin > vinyltriphenyltin > vinyltrimethyltin. Another relation is found in the case of organometallic compounds where the vinyl group is bound to the metal atom through a polar group or benzene ring. The acrylates and methacrylates of aryl and alkyl derivatives of tin, lead and mercury easily polymerize and copolymerize with vinyl monomers. New compounds also are the metal‐containing styrenes. We synthesized for the first time, under the conditions of a Leebrick‐Ramsden reaction, mercury‐ and lead‐containing styrenes. We investigated for the first time the polymerization and copolymerization as well as some properties of the following metallated styrenes: p‐phenylmercurostyrene, p‐styrenetriphenyllead, p‐styrenetriphenyltin. The compounds polymerize easily and copolymerize with vinyl monomers under conditions of radical reaction. A study of the reaction kinetics showed that the metallated styrenes polymerize at greater rates than unsubstituted styrene. The thermal stability of the metal‐containing styrenes decreases in the order: Sn > Pb > Hg. In studies on the polymerization of p‐vinylphenylmercury disproportionation was found to take place, leading to the formation of the symmetric divinyl derivative of diphenylmercury (I) and of diphenylmercury (II). Specially synthesized p‐vinylphenyl phenylmercury (I) was found to polymerize easily with the formation of an insoluble three‐dimensional polymer, not melting up to 250° and decomposing above this temperature with the liberation of metallic mercury. The polymer of (I) evidently has the structure
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The investigation shows that there is a considerable difference in the polymerization capacity of unsaturated organometal compounds and in the properties of the polymers and copolymers formed, depending upon the nature of the bond between the vinyl group and the metal atom.
Interfacial polycondensation of the hydrochlorides of dicarboxylic acids and diamines in the process of fiber formation
Authors: Mikhaĭlov N. V. , Maĭboroda V. I. , Nikolaeva S. S.
Published: April 2003

The method of interfacial polycondensation based on Schotten‐Baumann reaction is a new direction in the chemistry of high molecular compounds. The low temperatures and pressures at which this reaction takes place open up enormous potentialities for the synthesis of new polymers and the formatmionof articles from them directly in t.he course of the reaction.

Experiments were launched on the use of the intcrfacial polycondensation reaction for the formation of fibers and films directly during the polycondensation process. The monomer pairs used for the reaction were: sebacoyl chloride‐hexamethylenediamine, adipoyl chloride‐hexamethylenediamine, and terephthaloyl chloride‐hexamethylene‐ diamine. Polycondensation takes place differently in the fiber‐forming process from un‐ der stationary conditions and under conditions of mixing of the monomers. Fibers were spun in an upward flow of the solutions of the two monomers. The schematic and pa‐ rameters of the polycondensation reaction and fiber production are described. Experi‐ mental data were obtained on the yields and molecular weights of the polymers with re‐ spect to the monomer concentration and characteristics of the flow in the interfacial polycondensat.ion reaction in the process of fiber formation. These data were compared with the results from stationary conditions. Considerable difference has been shown to exist bet.ween the two modes of reaction, both in regard to the yield and to the specific viscosity of the polymers obtained. A tentative explanation of t,hese phenomena has been given. It was shown that, various additions play an important part in the interfacial polycondensation reaction. Cellulose derivatives, etc. were employed as the addition agents. A method was developed for spinning fibers in the process of polycondensation and the properties of the filaments formed have been investigated. Fibers of specific vis‐ cosity 1.23 have been obtained with a yield of 87y0. The fibers are capable of stretching to fourfold length and are typically hollow tubes in cross section. They are of crystal‐ line structure with strongly expressed fibrillarity, as was shown with the aid of an elec‐ tronic microscope.
Heterogeneous polycondensation
Authors: Akutin M. S. , Rodivilova L. A.
Published: April 2003

A study was made of the influence of various factors (time, concentration of the solutions, reagent ratios, nature of the solvent, stirring rate, etc.) upon the physical and physicomechanical properties of polyamides obtained from the chlorides of aliphatic and aromatic dicarboxylic acids. The polyamides were synthesized by means of heterogeneous polycondensation (at the interfacial boundar). The possibility of synthesizing polyamides containing heteroatoms (sulfur, phosphorus, etc.) in the polymer main chain has been investigated.
Synthesis of polyureas by the method of interfacial polycondensation
Authors: Alexandru L. , Dascălu L.
Published: April 2003

The interfacial polycondensation method is one of the main achievements recently made in the chemistry of high molecular compounds. Its theoretical importance and the expected practical results aroused considerable interest in the method. By its means polyamides, polyesters and polyurethanes have been synthesized. The present report is devoted to a presentation of the results of an investigation into the interfacial synthesis of polyureas. The synthesis was carried out starting from the diamines and phosgene:
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In this particular case the diamine used was hexamethylenediamine. The reagents were brought in contract in the form of their solutions, namely in aqueous alkali in the case of the amine and in various organic solvents in the case of phosgene. The effect of the solubility of the phosgene solvent in the hexamethylenediamine solvent (water) on the yield and reduced viscosity of the polyureides was investigated. It was found that with increase in solubility both the yield and the viscosity decreased. The influence of the molar ratio of the reagents, of excess NaOH, of the solution concentration, of the duration of reaction, of the temperature, on the degree of polymerization and reduced viscosity of the polymers was also studied. A decrease of the temperature flavors growth of molecular weight. For temperatures between 10°C. and −10°C. the viscosity varies within the limits 0.08 to 0.7.
Some observations on the application of generalized copolymerization equations to several systems involving highly polar monomers
Authors: Ham George E.
Published: April 2003

A generalized theory of copolymerization, including the significant effects of monomer units at any distance from the growing chain ending on the competitive addition of monomers has been recently published. The equations presented at that time are extended to cover various specific copolymerizations involving as one of the reactants a highly polar monomer such as maleic anhydride. Use of these expanded equations led to much improved correlation between experimental data and theoretical predictions. Pertinent reactivity ratios weighing the contributions of units nearby and at considerable distances from the growing chain endings were calculated from the data for the copolymer systems: styrene–maleic anhydride, methyl methacrylate–fumaronitrile, vinyl chloride–maleic anhydride, vinyl acetate–maleic anhydride, and isopropenyl acetate–maleic anhydride.
Graft copolymerization with perester side groups
Authors: Smets G. , Poot A. , Duncan G. L.
Published: April 2003

The kinetics of the graft copolymerization of styrene onto methyl acrylate (MA) and methyl methacrylate copolymers (MMA) containing tert‐butyl perester groups have been studied. The synthesis of these perester copolymers was carried out in two steps: (1) copolymerization of acrylyl chloride with methyl (meth)acrylate, and (2) reaction of the acrylyl chloride copolymer with tert‐butyl hydroperoxide. Further, these perester copolymers were usually treated with diazomethane in order to methylate any carboxylic group which might be present. The graft copolymers were separated from both hompolymers by progressive precipitation on addition of methanol to the chloroform solution of the copolymers. The stability of these perester copolymers has been considered and found to depend on whether there are acid groups in the copolymer. The first‐order rate constants and the activation energy of decomposition in the absence of acid groups have been evaluated. These values depend on the molar composition of the copolymer; an induced decomposition of peresters is favored by a high perester content, which is responsible for a decrease in Ea (26.8 instead of 29.6 kcal./mole). In the presence of free carboxylic groups, some of the perester groups decompose very rapidly, the energy of activation of their decomposition being only 15 instead of 25.6 kcal./mole for the slow step. The degree of conversion attained during the rapid step is a function of the stereochemical structure of the copolymer, and the rate of decomposition is much higher than that produced by the addition of external acid. With the MA perester the rate of grafting is proportional to the square root of the perester concentration while it is first order with respect to the monomer concentration. These dependences were found to hold also for the overall rate of polymerization (from the total weight increase) as well as for the grafting rate (from the isolated graft copolymer and its styrene content). The styrene content of the graft copolymer increases with monomer concentration (e.g., 53.8 and 75.3 for monomer concentrations of 2.6 and 6.1 moles/l., respectively). At low monomer concentration, grafting is greatly favored over homopolymerization; it is also enhanced by the viscosity of the solution. With the MMA perester also, the grafting rate obeys the square root law for the perester concentration and the first‐order dependence on monomer. However, the rate of grafting is practically independent of the styrene concentration over a large range. The relative importance of grafting over homopolymerization is in this case much less than with MA‐TBP, except at high dilution. Different interpretations are suggested in order to explain the very high and sometimes very low values of Rg/Rh, the ratio of the rate of grafting to the rate of hompolymerization. The different behaviors of the MA and MMA peresters are discussed.
Present status of the rubber elasticity theory
Authors: Ciferri A.
Published: April 2003

The development of the rubber elasticity theory is reviewed. Particular emphasis is given to the recent generalization of the elastic equation of state to the case where the chains display changes in internal energy with change in conformation and to the correlation between the elastic behavior of a crosslinked amorphous polymer and its dilute solution properties. Experimental results on the tension–temperature coefficient and on the stress–strain isotherm for polymer networks, which demonstrate the correctness of the generalized elastic equation of state, are surveyed.
Radiation‐induced ionic polymerization of isoprene
Authors: Tabata Yoneho , Shimozawa Ryosuke , Sobue Hiroshi
Published: April 2003

The γ‐ray‐induced polymerization of isoprene was investigated in the temperature range of ‐78° to 40°C. The following variables were studied: the dependence of polymerization rate on temperature; the effects of DPPH and pyridine on the polymerization at various temperatures; the dependence of the polymerization rate on dose rate at ‐78° and 20°C.; and the structure of the polyisoprenes obtained at various temperatures. the following results were obtained: (1) Although the Arrhenius plot of the polymerization rate did not yield a linear relation, the total polymerization rate was successfully separated into radical and ionic contributions. (2) The polymerization rate was proportional to the square root of dose rate at 20°C., whereas it was proportional to the first power of the dose rate at ‐78°C. (3) The structure of polyisoprene prepared at ‐78°C. is closely similar to that of cationically polymerized polyisoprene. The partially ionic mechanism of the radiation‐induced polymerization of isoprene was elucidated in this investigation. It was concluded that a cationic mechanism is operative at low temperatures whereas a radical mechanism predominates at higher temperatures.
Molecular weight distribution changes during the thermal breakdown of poly‐α‐methylstyrene
Authors: Cowie J. M. G. , Bywater S.
Published: April 2003

The changes in the molecular weight distribution accompanying the thermal depolymerization of poly‐α‐methylstyrene have been investigated. The original polymer, produced by anionic catalysis, had a narrow distribution of molecular weights, which facilitated measurement of the changes. The depolymerization when carried out in a thin polymer film at 226 and 236° caused extensive randomization of molecular weights at low conversions. In contrast, a similar depolymerization carried out in Decalin solution at 232° produced polymer maintaining the original sharp distribution. It is concluded that the kinetic chain length of the depolymerization reaction is much smaller than the molecular chain length in solid film reactions, but much greater than the molecular chain length in solution, under the experimental conditions used.
Sorption and diffusion in crystalline elastomers. Part II. Permeation of isomeric hydrocarbons in stretched rubber
Authors: Barrie J. A. , Platt B.
Published: April 2003

The permeabilities and diffusion coefficients of propane, n‐butane, and isobutane in stretched peroxide‐cured natural rubber have been measured at simple elongations of 0 to 400% in the temperature range 30 to 50°C. To minimize the effect of penetrant on the degree of crystallinity, only regions of low penetrant concentration were chosen. At elongations not sufficient to induce crystallization the permeability did not alter significantly on stretching. At higher elongations the permeability decreased with increasing crystallization. Over a long period of time and at a given temperature the permeability of a crystalline membrane decreased slowly toward an equilibrium value. No such behavior was observed with noncrystalline membranes either stretched or unstretched. Part of the decrease is accounted for by a corresponding slow increase with time in the degree of crystallinity and the remainder is attributed to a partial reorientation or redistribution of the crystallites as the system tends toward an equilibrium state. The data are analyzed in terms of a model in which the crystalline rubber is presented as a rectangular array of small cylindrical crystallites impermeable to penetrant and embedded in an amorphous matrix. To a first approximation the dependence of the permeability on crystallinity and temperature is represented satisfactorily by expressions based on the model. The data indicate that the crystallites may impose slight restrictions on the segmental mobilities in the amorphous regions, but the effect is not pronounced. Some differences between steady and transient state diffusion coefficients are explained in terms of “dead volume” which is present in the steady state of flow to a greater extent than in the transient state.
Crystallization of copolymers of ethylene glycol and diethylene glycol terephthalate
Authors: Golike R. C. , Cobbs W. H.
Published: April 2003

Rates of crystallization of polyethylene terephthalate and copolymers of ethylene glycol and diethylene glycol terephthalate were measured in the temperature range of 110 to 240°C.; this is the region of temperature in which the crystallization takes place at a measurable rate. It was found that the rate is defined by a modified Avrami type of equation over the entire temperature range of crystallization. Molecular motion, which limits crystallization at lower temperatures, was found to be a relaxation mechanism rather than simple viscous flow; to account for this, a modification of the Avrami type of equation was made. Data on copolymers of ethylene glycol and diethylene glycol terephthalate have shown that introduction of the longer chain yields a more flexible structure; hence at lower temperatures, where molecular motion is rate‐determining, the rate is increased. At higher temperatures introduction of the copolymer decreases the crystallization rate in the manner one would expect from the depression of the crystalline melting point.
The decomposition of benzoyl peroxide in polystyrene. II
Authors: Haas Howard C.
Published: April 2003

Polystyrene films containing benzoyl peroxide were heated in air at 73 and 90°C. and the products of decomposition were investigated. The products are benzoic acid, phenyl benzoate, polystyrene benzoate, and carbon dioxide. The same products, in very similar quantities, are formed at both 73 and 90°C., suggesting that diffusion of radicals out of the polymer cage is not an important occurrence either above or below the apparent second‐order transition temperature of polystyrene. The change in the temperature dependence of peroxide decomposition rate above 80°C. seems to be associated with a greater ease of reaction of benzoyloxy radicals with the walls of the polymer cage above the glass temperature. Considerably more ester formation and less carbon dioxide evolution are observed in this decomposition than when benzoyl peroxide is decomposed in benzene or toluene. Attack by benzoyloxy radical occurs on both the ring and backbone of polystyrene, the backbone attack seeming to take place predominantly on the secondary carbon atoms of the backbone.
Some aspects of the crosslinking and degradation of gelatin molecules in aqueous solution irradiated by 60Co γ‐rays
Authors: Tomoda Yoshitada , Tsuda Minoru
Published: April 2003

When an aqueous gelatin solution was irradiated by γ‐rays from a Co60 source, crosslinking occurred if nitrogen gas was passed through the solution, while degradation occurred with irradiation in an oxygen atmosphere. Empirical equations for the changes of the viscosity and the number of inter‐ or intramolecular crosslinks were obtained in each case and the phenomena were explained on the basis of an assumed reaction mechanism. The general equation for crosslinking is [η] = [η]Oekar, where [η] represents intrinsic viscosity of the solution and r is the γ‐radiation dose. The number of inter‐molecular cross links [R‐R]inter is given by [R‐R]inter = N0 (1 ‐ e‐kr), and the number of intramolecular cross links by [R‐R]intra = N0(kr + e‐kr ‐ 1), where N0 is the initial number of gelatin molecules. In the case of degradation, the variation at intrinsic viscosity and the number of intermolecular cross links with radiation dose is given by the equations: [η] = [η]0[N0/(N0 + k′r)]a and [R—R]inter = −k′r.
Evaluation of the terpolymer composition equation
Authors: Kahn Donald J. , Horowitz Hugh H.
Published: April 2003

The equations describing the relationships between polymer composition and feed composition in a three‐monomer polymerization have been experimentally verified at high monomer conversions for the first time. In this paper, a three‐component system involving vinyl acetate‐octyl fumarate‐N‐vinyl pyrrolidone was analyzed. The six reactivity ratios, or relative reaction rate constants, were either taken from previous literature or determined from two‐component systems. The differential terpolymerization equations could be integrated analytically in special cases, owing to the negligibility of some of the terms, but a more precise technique was to integrate numerically with a digital computer. Two feed compositions were polymerized to various levels of fumarate conversion covering the entire range. The extent of conversion was determined polarographically. Average terpolymer compositions, determined by elemental analysis, checked with values predicted by the mathematical model well within experimental error. The calculations also showed that the instantaneous terpolymer composition can vary considerably during a batch polymerization and give rise to a spectrum of polymer properties.
The effect of temperature and strain rate on the stress‐strain curve of oriented isotactic polypropylene
Authors: Hall I. H.
Published: April 2003

The effect on the stress‐strain curve of oriented isotactic polypropylene of passing through the “glass transition” region, either by increasing the strain rate or decreasing the temperature, is to increase sharply the modulus at strains up to about 5% and the stress at break. The modulus at higher strains and the elongation at break are little affected, and even at a temperature of 90°K., well below the transition region, the extension at break is as large as 13%. Another effect of decreasing temperature or increasing strain rate is to remove the nonrecoverable components of the extension of the material. This is a different effect from the transition phenomenon since it occurs at a different combination of strain rate and temperature. The results at different rates of strain are described from the point of view of viscoelastic theory, and a treatment is described which gives a better description of the behavior than the more conventional spring‐dashpot models.
A theory of the thermodynamic behavior of nonelectrolyte solutions. VII. Partial miscibility in the system polystyrene–cyclohexane
Authors: Maron Samuel H. , Nakajima Nobuyuki
Published: April 2003

Maron's theory of the thermodynamics of nonelectrolyte solutions has been used to obtain from published osmotic pressure, light‐scattering, and partial miscibility data for the system polystyrene‐cyclohexane (μ° – σ°) and σ° values as functions of molecular weight and temperature. These functions were combined then with intrinsic viscosities to calculate the partial miscibility curves for five samples of polystyrene of varying molecular weight. Except for minor discrepancies, which are shown to be due to molecular weight heterogeneity, the calculated plots are in good agreement with the experimental results. The data have also been used to evaluate the interaction parameters at the points of critical miscibility. These calculations confirm the predictions of Maron and Nakajima that for infinite molecular weight these parameters go to the limits μc° = 2/3, σc° = 1/6, (μc° – σc°) = 1/2, and μc = 2/3.
The influence of the structure of ion‐exchange polymers on ion‐exchange between polymers and electrolytes in solutions
Authors: Saldadze K. M.
Published: April 2003

The effect of the number of crosslinks in polymers on the ion exchange process has been investigated, assuming the exchanger to be a polyelectrolyte. An increase in the number of crosslinks (divinylbenzene content from 2 to 16%) has been found to cause no change in the character of the adsorption both in homovalent as well as heterovalent exchange. The processes obey the law of mass action regardless of whether contact is made between a polymer with varying divinylbenzene (DVB) content and solution of constant concentration or between one with constant DVB content and variously diluted solutions. With change in the crosslinking agent content of the polymer, the selectivity of ionic adsorption, which is determined by the property and size of the exchanging ions, varies. Changes in the number and arrangement of active groups in the polymer network have different effects on the ion exchange processes. An increase in the amount of active groups without marked changes in the swelling properties of the resin has no noticeable effect on the ion exchange processes, but as the concentration of active groups is increased with simultaneous increase in the specific volume of the resin considerable change in the selectivity of the ions being adsorbed takes place during the ion exchange process. With varying arrangement of the same active groups in the network of the ion exchanger, if different crosslinking agents are used in its synthesis its properties change, depending upon the medium in which the exchange is taking place. For example, the exchanger EDE‐10P synthesized on the basis of polyethylenepolyamine and epichlorohydrin may be considered to have practically only secondary and tertiary amine groups if one neglects a small amount of active groups of the quaternary ammonium bases. This exchanger adsorbs the anions of acids (H2SO4 and HCl) in acid medium and possesses a total exchange capacity of 10.5 meq./g. From a neutral medium (0.1N solution NaCl) it adsorbs about 0.95 meq./g. Cl−. On contact of the OH form of the resin with 0.1N CuSO4 and 0.02N H2SO4 it adsorbs 6.08 meq./g. SO42− and 5.75 meq./g. Cu2+ and on contact with 0.1N ZnCl2, 6.2 meq./g. Cl− and 5.92 meq./g. Zn2+. Under the same conditions the exchanger AN‐2F synthesized from phenol, polyethylenepolyamines, and formaldehyde and containing active N and NH groups practically adsorbs no copper. The capacity for CuSO4 adsorption by the anion exchanger EDE‐10P is not simple molecular sorption taking place with various exchangers on contact with acid and salt solutions. In this case, as has been demonstrated, complex compounds such as [(R2NH)2Me(H2O)2]X2 and [(R3N)2Me(H2O)2]X2 are formed. Such complexes are not formed by other anion exchangers containing secondary and tertiary amino groups.
Copolymerizations with triallyl cyanurate, triallyl isocyanurate, and diallylmelamine
Authors: Roth R. W. , Church R. F.
Published: April 2003

Reactivity ratios for the copolymerization of triallyl eyanurate, triallyl isocyanurate, and diallylmelamine with methyl methacrylate, styrene, and vinyl acetate have been determined. Integral composition distribution curves have been determined for the triallyl cyanurate‐methyl‐methacrylate system.
Cumene hydroperoxide‐initiated radical polymerization
Authors: Tobolsky A. V. , Matlack L. R.
Published: April 2003

The initial rates of solution polymerization of styrene and methyl methacrylate initiated by cumene hydroperoxide were determined at several temperatures. A new method of analysis of the kinetic data is presented. The results led us to conclude that the radicals which initiate polymerization are produced exclusively by bimolecular reactions, namely, a bimolecular reaction between hydroperoxide and solvent. For the latter reaction, benzene can be classified as very inert, but dimethylaniline, pyridine, and benzyl alcohol are quite active. Rate constants for the various initiating reactions are tabulated.
Rearrangement of a polymethylsiloxane by hydrogen chloride
Authors: Mayo Frank R.
Published: April 2003

Linear decamethyltetrasiloxane (MD2M) was treated with hydrogen chloride in the presence of various amount of water or methanol at room temperature. In the presence of water, the rate and extent of cleavage and rearrangement increased with the concentration of hydrogen chloride and the volume of the aqueous phase. In a slow stream of hydrogen chloride gas, significant proportions of the MD2M were lost as chlorosilane vapors. Until an aqueous phase appears, M2D2 is fairly stable to dry hydrogen chloride. It is also stable to dilute aqueous hydrogen chloride, but, with an equal volume of saturated aqueous hydrogen chloride, 10–20% of the MD2M may react in an hour. Rearrangement and cleavage are accelerated by methanol and by tetrahydrofuran. The significance of these results is discussed.
The nature of the end products from the enzymic treatment of tropocollagen and collagen fibrils
Authors: Barkin Stanley M. , Oneson Irving
Published: April 2003

Treatment of a solution of rat tail tendon collagen in acetate buffer with a proteolytic enzyme (ficin) led to a monodispersed solution of rodlike particles whose dimensions were 12.6 A. in diameter and 2400 A. in length. Similar enzymic treatment of dispersions of steer tendon collagen fibrils resulted in a disaggregation of the fibrils to a solution of particles of essentially similar dimensions. The nature of the enzymic attack in relation to the structure of the substrate is discussed.
Polymerization of vinyl monomers containing boron II. p‐vinylphenylboronic acid
Authors: Pellon Joseph , Schwind L. H. , Guinard M. J. , Thomas W. M.
Published: April 2003

p‐Vinylphenylboronic acid was prepared by the reaction of p‐vinylphenyl magnesium chloride with tributyl borate. It is similar to styrene in respect to rate of free radical polymerization. Loss of boron is not significant during polymerization or handling. The polymer is a polyelectrolyte, soluble only in liquids containing some water. Films are clear, colorless, and brittle. On heating the polymer first becomes crosslinked by dehydration, then undergoes severe weight loss at 380 to 400°. Copolymerization behavior is that of an active monomer with an electron‐deficient vinyl group.
Copolymerization of methacrylic anhydride with vinyl monomers
Authors: Hwa Jesse C. H. , Miller Leon
Published: April 2003

Copolymerizations of methacrylic anhydride and a variety of common types of vinyl monomers were conducted in bulk and in solution at 60–80° with benzoyl peroxide catalyst. The copolymers were characterized by conversion, solubility in hot dimethyl sulfoxide, elementary analysis, and infrared spectroscopy. A copolymer composition equation was derived for a special divinyl–vinyl system in which the divinyl monomer would cyclize extensively during polymerization and give rise to soluble, although perhaps branched, copolymers. The results showed that both soluble and insoluble copolymers were obtained, depending on the comonomer used and experimental conditions under which the copolymerization was carried out. In general, soluble copolymers were formed under the following conditions: (a) the less reactive the comonomer in free radical copolymerizations; (b) the greater the dilution; (c) the greater the difference in the moles of the two components in charge; and (d) the lower the conversion. According to reactivity ratio determinations and a comparison with published data, the anhydride ring radical behaved like a methyl methacrylate radical. The key step which led to gelation was believed to be “ring interruption” by the comonomer (CH2 = CHR):

The question why methacrylic anhydride does not gel in homopolymerization, however, still remains unresolved.
Investigations of the chemical conversions of polycarbonates
Authors: Ya. Yakubovich A. , Ya. Gordon G. , Maslennikova L. I. , Grobman E. M. , Tret'Yakova K. I. , Kokoreva N. I.
Published: April 2003

Polycarbonates, in particular poly‐4,4′‐bis(hydroxyphenyl)‐2,2‐propane carbonate, are distinguished by their thermal stability and may be processed at temperatures about 300°. The present report deals with some chemical conversions of this polymer, taking place in solution and in the molten state. In the fractional precipitation of the polymer from chloroform solutions by methyl alcohol an enhanced yield in the low molecular fraction is observed, the latter continually forming even on repeated precipitation. If a small amount of methanol, insufficient to precipitate the polymer, is added to the chloroform solution, a gradual fall in viscosity (which does not occur in absence of the alcohol) is observed. The reaction is accelerated in the presence of hydrogen chloride. Such precipitants as acetone and petroleum ether do not cause this effect. Alcoholysis is a characteristic reaction of the polycarbonates, taking place at a relatively high rate. An alcoholic solution of alkali will decompose the polycarbonate at room temperature and especially rapidly (within a few minutes) on boiling. In this way one may obtain with high yield bisphenol used for the synthesis of the polymer. The melting of polydisperse polycarbonates (ca. 300°) in the absence of atmospheric oxygen leads to a very rapid (10–60 min.) levelling of the molecular chain lengths and hence to decrease in polydispersity (according to fractional precipitation data), causing a corresponding fall in the viscometrically determined molecular weights. Such levelling annuls the harmful effect of the low molecular fractions on the properties of the material. At higher temperatures (350°) decarboxylation (evolution of CO2) is quite marked, and the formation of a certain amount of three‐dimensional polymer may be observed. Polycarbonates prepared by the heterophase polycondensation of phosgene with phenolates, for instance, 4,4′‐bis(hydroxyphenyl)‐2,3‐propane and containing hydroxyl and acyl chloride endgroups are capable of undergoing further polycondensation on heating to 270–300°C. for 30–60 min. or more. Hydrogen chloride is evolved. As a result the mean viscometric molecular weight may increase three‐ to fourfold in comparison with the initial compound. Additional polycondensation in the melt may also proceed by another pathway, without hydrogen chloride evolution but as the result of the elimination of a certain amount of 4,4′‐bis(oxyphenyl)‐2,2‐propane on endgroup interaction. This reaction is catalyzed by small quantities of titanium alcoholates. The high lability of the ester links in polycarbonates may also be illustrated on the example of the interaction between these polymers and other esters, in particular with polybis(phenyl)‐2,2‐propane terephthalate [OC6H4C(CH3)2C6H4OCOC6H4COO]. The reaction taking place without catalyst at temperatures above 300° results in a mixed polyster carbonate with composite properties.