bluuebunny/crossref_metadata_2025_split huggingface dataset:
Grafting onto cellulosic macromolecules through chain transfer to mercaptoethyl side chains. II. Mechanism of the process
Authors: Chaudhuri D. K. Ray , Hermans J. J. 
Published: April 2003

AbstractThe data that were presented in Part I are compared with theory. It is found that the weight increase of a mercaptoethylated cellulose acetate film during polymerization of styrene in the presence of this film is proportional to the initial monomer content and to 1 − exp {−bt} where t is the time and b a constant proportional to (catalyst concentration)1/2 times (initiation efficiency)1/2. This equation is in accordance with the theory of grafting developed by Fox and co‐workers, when the monomer conversion is low, but it is found experimentally that its validity extends well beyond values of the monomer conversion for which the equation should no longer represent a good approximation. (1) The composition of the film and therefore the monomer concentration and the rate constants change during grafting. (2) When grafting is high it becomes impossible quantitatively to remove the homopolymer by extraction of the film. (3) Chain transfer takes place not only to SH groups but also to nonmercaptoethylated parts of the cellulose acetate, It is believed that three causes are responsible for this result.
Peroxidation of isotactic polybutene
Authors: Beati E. , Severini F. , Toffano S. 
Published: April 2003

AbstractThe reaction of direct peroxidation at 75–90°C. and the simultaneous or successive ones of degradation of the isotactic poly‐α‐olefins are followed through analytical measurements of the total peroxide oxygen content (dialkyl peroxides + alkyl hydroperoxides) and intrinsic viscosity measurements. The results obtained from the autocatalytic oxidation and those from operating in the presence of a volatile initiator (tert‐butyl hydroperoxide), either containing labelled carbon or not, are described and compared.
Isotactic trans‐1,4 polymers of 1,3‐pentadiene
Authors: Natta G. , Porri L. , Corradini P. , Zanini G. , Ciampelli F. 
Published: April 2003

AbstractCrystalline polymers of 1,3‐pentadiene, which are composed of trans‐1,4 units and show an isotactic configuration of the tertiary carbon atoms, have been obtained with the use of the heterogeneous Al(C2H5)3VCl3 catalytic system. The cis or trans isomer of pentadiene yields polymers that are more stereoregular than those obtained from mixtures of the two isomers. Isotactic trans‐1,4‐poIypentadiene may exist in two modifications: crystalline and paracrystalline (unidimensionally regular). The two modifications are characterized by different x‐ray spectra and different densities. trans‐1,4 Isotactic polypentadienes contain tertiary carbon atoms which are actually asymmetric. This permitted obtaining optically active polypentadienes by using polymerization catalysts prepared from optically active aluminum trialkyls.
cis‐Tactic polybutadiene: Solubility, [η]–M relations in different solvents, and molecular conformation
Authors: Danusso Ferdinando , Moraglio Giovanni , Gianotti Giuseppe 
Published: April 2003

AbstractSeveral samples of cis‐tactic polybutadiene prepared by stereospecific catalysis and having a cis unit content of about 98%, were fractionated by fractional precipitation techniques. Some of the central fractions obtained were examined by viscometric, osmotic, and sedimentation methods in dilute solution. [η]–M relations were determined for benzene and toluene at 30°, and for isobutyl acetate at 20.5°C., the latter solvent being at ϑ conditions. Configurational parameters of unperturbed molecules and interaction affinity in good solvent were calculated and are compared with those of known hydrocarbon polymers.
Structure of isotactic polyaldehydes
Authors: Natta G. , Corradini P. , Bassi I. W. 
Published: April 2003

AbstractThe crystalline polymers having a polyacetalic chemical structure, as obtained by us by polymerization at low temperature of aldehydes in the presence of stereospecific catalysts formed by metalloorganic compounds, show an isotactic structure. The chain conformations of different isotactic polyaldehydes are discussed, and in particular the crystalline structures of polyacetaldehyde, of poly‐n‐butyraldehyde and of polypropionaldehyde are described. The polymeric chains of these polyaldehydes have a fourfold helix conformation with a repetition period of 4.8 A., and the packing of the macromolecules corresponds to that of the tetragonal I41/a space group. Around each fourfold screw axis present in the unit cell, isomorphous anticlined macromolecules can statistically vicariate.
Morphology of dendritic polyethylene crystals
Authors: Geil P. H. , Reneker D. H. 
Published: April 2003

AbstractThe dendritic crystals of polyethylene described in this paper illustrate many details of the morphology of polyethylene crystals including the development of spiral growths, delineation of fold domains, the attachments between adjacent lamellae, and fracture behavior of single lamellae. Definitions of terms useful in the description of lamellar crystals of polymer molecules are also given.
The synthesis of silico‐organic polymers on the complex catalyst (C2H5)3Al+TiCl4
Authors: Nametkin N. S. , Topchiev A. V. , Durgar'Yan S. G. 
Published: April 2003

AbstractOrganosilicon polymers with silico‐carbon units in the main chain are of considerable interest. The initial monomers for the synthesis of the polymers may be alkenylsilanes. In the present work it is shown that polymerization of alkenylsilanes may take place on a complex (C2H5)3AlTiCl4 catalyst. The polymerization was carried out at 50–70°C. with n‐heptane as solvent. The effect of the triethylaluminum:titanium tetrachloride ratio on the yield and properties of the polymers obtained was also investigated. Highest yields were obtained at (C2H5)3Al:TiCl4 molar ratios of 1:2, 1:3, and 1:4. Both crystalline and liquid polymers are formed. On polymerization of methylphenyldiallylsilane about 30% solid polymer is produced. The isotactic portion of this solid polymer (after extraction with ether) has a melting point of 400–410°C. The copolymerization of dimethylphenyldiallysilane and methylphenyldiallylsilane with propylene in the liquid phase was also studied. A number of physicochemical properties of the polymers were investigated.
Polymers containing germanium
Authors: Kolesnikov H. S. , Davydova S. L. , Klimentova N. V. 
Published: April 2003

AbstractMethacrylyltriethylgermanium was synthesized and shown to be capable of polymerization and of copolymerization with other unsaturated compounds. The polymers and copolymers were studied in order to determine the effect of incorporation of the tri‐alkylgermanium group R3Ge on properties of the polymers.
Polymerization reactions on insoluble molecularly disperse substances
Authors: Kargin V. A. , Kabanov V. A. 
Published: April 2003

AbstractAtomic and molecular dispersions of inorganic solids in monomer media has been found capable of giving rise to highly active polymerization centers effective at low tempera‐ tures It was shown, using BeCl ZnClz, LiC1, TiC1, and RloOj, that salts and oxides which in the form of perfect crystals are not polymerization catalysts, in the molecular disperse state or with highly defective structures may cause the polymerization of a number of monomers (styrene, a‐methylstyrene, isoprene) at their melting points. A study was made of the initiating capacity of some metals in molecular mixtures with monomers. It was shown that with suchamixtures of Mg and acrylonitrile, methyl methacrylate, or methyl acrylate rapid low‐temperature polymerization in the solid state takes place. The polymerization is induced by radicals formed on reaction of Mg with the monomers. Similar conversions may occur in the presence of other metals (Hg, Zn, Cd). The methyl methacrylate produced in this way was found to have an isotactic structure. Hence the part played by preliminary ordering of the monomer on the formation of the polymer microstructure has been demonstrated. Studies with the crystalline salts of acrylic and methacrylic acids show that it is possible to initiate poly‐ merization in the solid phase by the formation of defective crystal structures in the system. This may be arcomplished by heterogeneous chemical reactions and intensive mechanical dispersion of the solid monomers.
Radical decomposition of various peranhydrides and peresters
Authors: Razuvaev G. A. , Terman L. M. , Likhterov V. R. , Etlis V. S. 
Published: April 2003

AbstractWe have studied the kinetics and the products of the thermal degradation of acetylcyclohexylsulfonyl (I), dibenzyl (II) and dicyclohexyl peroxide carbonate (III) in various solvents. The kinetic data show that the degradation is first‐order with respect to the peroxide. The activation energies for the reaction in benzene, isopropyl alcohol and carbon tetrachloride have been calculated. It is suggested that the primary process is decomposition of the peroxide to free radicals according to the scheme:
magnified imageIn solvents which easily give up hydrogen, such as isopropyl alcohol, hydrogen is removed with the formation of sulfonic acids from I and the corresponding alcohols from II and III:
magnified imageIn benzene and carbon tetrachloride the ensuing free radicals disproportionate, forming chiefly unsaturated sulfonic acids on degradation of I, and carbonyl compounds and alcohol on degradation of II and III.
magnified imageIt should be mentioned that no products of interaction with the solvent were found on degradation of peroxydicarbonates in benzene. In the degradation of (I), a resin was isolated, of which the nature was determined by decomposition in C14‐labeled benzene. Also in the degradation of I, methyl sulfonate was detected in amounts which underwent almost no change on variation in concentration of I. This indicates that the methyl sulfonate was formed by the molecular decomposition of the initial peroxide:
magnified image
Synthesis of crystalline polyvinylcyclohexane
Authors: Mushina E. A. , Perel'Man A. I. , Topchiev A. V. , Krentsel B. A. 
Published: April 2003

AbstractThe least known field of stereospecific polymerization is the polymerization of vinylcycloalkanes. At the same time polyvinylalkanes and especially polyvinylcycloalkanes may be of considerable interest as a new class of crystalline polyvinyl compounds. With this in mind the synthesis of polyvinylcyclohexane has been carried out and its properties have been investigated. Polymerization of vinylcyclohexane takes place in the presence of titanium tetrachloride and isobutylaluminum or of chromium oxides on aluminum silicate. The polymer obtained with different catalysts and under varying conditions (temperature, solvent, catalyst concentration, etc.) according to x‐ray data has a high degree of crystallinity. The melting point is 325° and the intrinsic viscosity from 0.5 to 1.5. A characteristic feature is its good solubility in naphthenic and aromatic hydrocarbons. The structure of the polymer has been established and thermomechanical curves have been determined for polymers obtained on various catalysts.
Some problems of polycondensation in suspensions
Authors: Lesek F. , Khromeček R. 
Published: April 2003

AbstractFrom a hydrodynamic standpoint an anology exists between suspension polycondensation and suspension polymerization. The hydrodynamics of polycondensation have been less thoroughly investigated for water/oil than oil/water systems. From a physicochemical standpoint suspension polycondensation differs from suspension polymerization in a number of features. In the presence of excess surface‐active agent an emulsion is formed only in exceptional cases. The amount of surface‐active agents in suspension polycondensation exceeds that employed in polymerization. In the latter case, traces of surface‐active substances are used; with increase in their concentration a tendency towards block polymerization appears. The course of the reaction depends to a large extent upon the nature of the stabilizer. A stabilizer similar in character to the condensation system is advantageous. It may be assumed that in some cases an acid stabilizer enhances concentration of the reaction catalyst at the interfacial boundary. The nature of the components of the system has a considerable effect on the polycondensation. In the future the effect of the disperse phase on the course of the reaction will be investigated. Despite the close values of density and interfacial tension the use of such hydrocarbons as xylene and tetrachloroethane is more suitable than the use of chlorobenzene or tetrachloroethylene. The opinion exists that suspension polymerization is mainly block polymerization. This hypothesis does not seem to hold in the case of the surface layer of globules. In suspension polycondensation the degree of homogeneity of the initial components plays an important part, particularly on a commercial scale.
The catalytic action of some metal compounds on the preparation of polyurethans
Authors: Blagonravova A. A. , Levkovich G. A. , Pronina I. A. 
Published: April 2003

AbstractA study has been made of the catalytic effectof various salts on the formation of poly‐ urethans. The main attention was paid to the catalytic action of zinc compounds (zinc oxide, zinc acetate, and basic zinc chromate) in the reaction of 2,4toluene diisocyanate with hydroxyl‐containing compounds (β‐hydroxyethyl adipate and ethylene glycol). The experiments showed that the rate of change of isocyanate group content during poly‐ urethan formation greatly depends upon the cwntent of the zinc compounds. A neces‐ sary condition for the appearance of a catalytic effwt was found to be preliminary contact (before isocyanatc addition) of the zinc compound u ith β‐hydroxyethyl adipate. It was also found that after contact with the zinc compound the ester alone wiII react with the isocyanate at the same rate as in the presence of the catalyst. The same relation were also found for the system ethylene glycol‐toluene diisocyanate. The reaction is also ac‐ celerated by the zinc compounds, separation of the glycol after contact not lowering the velocity. Acids like anthranilic, o‐phthalic and acetic have been found to lower the rate of change of isocyanate groups in the systems containing catalysts. The strongest inhibit‐ ing effect is exerted by anthranilic acid. The catalytic activity of zinc acetate has been shown to exceed that of zinc oxide. The effect of the time of preliminary contact on the magnitude of the catalytic action in zinc acetate‐ester systems is much less expressed then in zinc oxide‐ster systems. Catalysts of the reaction between isocyanate and hydroxyl‐ containing compounds may be divided into two groups. To one group belong the oxides and salts of some metals: typical representatives of the other group are organic bases. A comparison of the catalytic activities of zinc oxide and pyridine showed the latter to be of considerably lower activity. Ways have been found for the stabilization of pigmented polyurethan systems, making it possible to greatly increase the variety of pigments rec‐ ommended for use in polyurethan paints.
On the polymerization of polyfunctional compounds
Authors: Arbuzova I. A. , Rostovskiĭ E. N. 
Published: April 2003

AbstractThe present investigation is a two‐sided approach to polyfunctional compounds, namely: (1) polymerization of unsaturated monomers containing reactive groups, in particular, methylol derivatives of unsaturated acids; (2) cyclopolymerization of diolefinic monomers. In the first method of attack conditions have been investigated under which soluble, linear polymers are formed. Our studies have thrown light on the mechanism of reactions facilitating the formation of crosslinks. From a study of the polymerization of methylolacrylamide monomers (in collaboration with L. M. Novichkova) it became possible to direct the reaction towards the formation of soluble, linear polymers. The possibility of further conversions such as transformation of the linear polymers to three‐dimensional ones leads to the polymerization‐condensation concept of polymer formation. This is of particular interest, since it provides the basis for predetermined modification of polymer properties (for example, elimination of flow, increase of strength, chemical resistance, etc.). The reactivity of the methylolamide group allows the use of the compounds in question for these purposes, for instance as copolymer with acrylonitrile. The second method of attack is the cyclic polymerization of symmetrical and unsymmetrical diolefine monomers and of compounds arising in the process of polymerization of 1–6 unsaturated systems. Earlier, Butler, Marvel, Jones and others pointed out the formation of linear cyclic polymers in the polymerization of symmetric divinyl and diallyl monomers unsaturated in the 1,5‐ and 1,6‐positions. The authors of the present work have synthesized a number of acetals of vinyl alcohol and ascertained the conditions for the formation of linear polymers consisting of six‐membered cyclic repeating units connected by methylene groups. Polymerization of asymmetric diene monomers was investigated using as examples vinyl crotonate, bulk polymerization of equimolecular quantities of allyl alcohol and maleic anhydride, and copolymerization of maleic anhydride with dibenzalactone. The establishment of the possibility of divinylacetal polymerization according to a cyclic mechanism makes it possible to outline new ways of synthesis of the acetals of polyvinyl alcohol. It has also been found that in the polymerization of the asymmetric diene monomers vinylcrotonate and monoallyl maleate, soluble, linear polymers are formed, of which the properties indicate that cyclization takes place in the course of the reaction.
A new redox system for vinyl polymerization in aqueous medium
Authors: Menon C. C. , Kapur S. L. 
Published: April 2003

AbstractA new redox system for vinyl polymerization comprising hydrazine, cupric ions and molecular oxygen is described. The influece of the pH of the medium, the monomer concentration, and the concentration of cupric ions on the rate of polymerization and the rate of hydrazine disappearance is studied. The results are explained in terms of a mechanism involving one‐electron oxidation of hydrazine by a cupric ion to produce the hydrazyl radical, the conversion of cuprous ions to cupric ions by atmospheric oxygen which involves radical intermediates capable of initiation of polymerization and a termination reaction involving the polymeric radical, cuprous ion and oxygen.
Communication on oligomers. XXIII. Synthesis of amino alcohols by the action of lithium aluminum hydride on oligamides of ε‐aminocaproic acid
Authors: Zahn H. , Gleissner A. 
Published: April 2003

AbstractThe synthesis of the homologous series of (I) amino alcohols H[NH(CH2)6]nOH, wheren= 1–9, and (II) their methylated products CH3[NH(CH2)6]nOH, wheren= 1–9, is described. These compounds are easily prepared by lithium aluminum hydride reduction of oligamides of ϵ‐aminocaproic acid. Nylon 6, the crystalline part of silk, and the tetrapeptide Gly‐Ala‐Gly‐Ala were also to their corresponding amino alcohols.
Coordination compounds of p‐(1,3‐butanedione)‐N‐phenylglycine
Authors: Mattison Louis E. , Phipps Martha S. , Kazan John , Alfred Lillian 
Published: April 2003

AbstractA new chelating agent containing two different chelating systems in the same molecule was synthesized: p‐(1,3‐butanedione)‐N‐phenylglycine. Simultaneous coordination of this molecule with divalent lead and uranyl ions resulted in a bimetallic chelate polymer. Also prepared were coordination polymers of the chelating agent with the following divalent metal ions: beryllium, copper, magnesium, nickel, uranyl, and zinc. Thermal analysis data show that the beryllium, zinc, and uranyl polymers are exceptionally stable, with from 0.39–0.65% weight loss per hour at 200° in air. Four monomeric chelates were also investigated.
Radiation‐induced ionic polymerization at low temperature
Authors: Tsuda Yoshizo 
Published: April 2003

AbstractThe copolymerization, by means of ionizing radiation, of acrylonitrile with styrene or methyl methacrylate was investigated at ‐78°C. in bulk and in various solvents. The copolymerization proceeds by a cationic mechanism in methylene chloride solution, by a free radical mechanism in bulk, and by both an anionic mechanism and a free radical mechanism in dimethyl formamide, diethylamine, toluene, and ethyl bromide solutions. The rate of anionic polymerization of acrylonitrile increases with dilution of monomer. The cationic polymerization in methylene chloride solution was shown to be caused by the catalytic action of hydrogen chloride which is formed from the irradiation of chlorinated hydrocarbon. It was concluded that the main factor in the induction of an anionic polymerization of acrylonitrile is the large reactivity of the monomer in anionic polymerization.
Suspension polymerization of vinyl chloride at low temperature with the use of monomer‐soluble redox initiators
Authors: Konishi Akio , Nambu Keiichi 
Published: April 2003

AbstractSuspension polymerization of vinyl chloride was carried out at temperatures of ‐30° to +30°C. with the use of a monomer‐soluble oxidation‐reduction initiator system. A typical initiator system was composed of lauroyl peroxide and ferrous n‐caproate. The effects of temperature, molar ratio of peroxide to reducing agent, and total concentration of initiator upon the rate and degree of polymerization were observed. The activation energy of the overall rate of polymerization was 6.5 kcal./mole. Experimental evidence which may serve to elucidate the mechanism of the redox reaction in the nonemulsified system is discussed.
High frequency effects in polyelectrolyte solutions
Authors: Johnson G. A. , Neale S. M. 
Published: April 2003

AbstractConductivity measurements of solutions of sodium polymethacylate (PMA), sodium carboxymethyl cellulose (CMC), and sodium alginate (AA) are presented. Measurements were made in the frequency range of 1 to 30 Mcycles/sec. The increment of electrical conductivity is taken as a measure of the dielectric loss occurring in the solution. The theories of Debye,1 Debye–Falkenhagen,2 Maxwell–Wagner,3 and the recent ionic model proposed by O'Konski4 are discussed and it is shown that the results can be satisfactorily explained only with an ionic model of the form of O'Konski's. Previous work is shown to fit in satisfactorily with this theory. In a few cases measurements of loss factors and dielectric constants are presented, and are shown to give additionnal support to the model of O'Konski.
The kinetics of the thermal degradation of polystyrene and polyethylene
Authors: Anderson David A. , Freeman Eli S. 
Published: April 2003

AbstractThe nonisothermal method of Freeman and Carroll is used to investigate the kinetics of the thermal degradation of polyethylene and polystyrene. The reactions were studied thermogravimetrically under a vacuum of 1 mm Hg. Decomposition appears to occur in stages. The rate parameters were determined for each region of reaction. Mechanisms of degradation are suggested. The results of this investigation are compared with the kinetic parameters reported by other investigators for the decompostion of these polymers.