bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization by oxidation coupling. I. A study of the oxidation of 2,6‐diphenylphenol to poly(2,6‐diphenyl‐1,4‐phenylene ether)
Authors: White Dwain M. , Klopfer Howard J. 
Published: April 2003

AbstractThe synthesis of poly(2,6‐diphenyl‐1,4‐phenylene ether), by the oxidative coupling of 2,6‐diphenylphenol has been studied. Procedures were found which demonstrated that polymers of very high molecular weight \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\overline M _n > 200{\rm 000; }\left[ \eta \right]_{{\rm CHCl}_{\rm 3} }^{25^\circ {\rm C}} > 1.1{\rm }{{{\rm dl}} \mathord{\left/ {\vphantom {{{\rm dl}} g}} \right. \kern-\nulldelimiterspace} g}} \right) $\end{document} could be made with a copper‐amine catalyst system. A low nitrogen‐to‐copper ratio (1 N atom/Cu atom) was necessary to obtain the very high molecular weights under the conditions of these reactions. A variety of amines formed active catalysts; the effectiveness of mono‐ and bis‐ primary, secondary, and tertiary amines were compared. Effects of the type of copper halide, reaction temperature, desiccants, addition rates of 2,6‐di‐phenylphenol, and solvents were also examined. Samples of polymer were isolated at different times during the polymerization. Measurements of viscosity, osmotic pressure, light scattering, gel permeation, phenolic hydroxyl groups, and nitrogen content were made on various samples over a range of intrinsic viscosities of 0.05–0.59 dl/g. A very narrow molecular weight distribution was found for all samples. Hydroxyl endgroup analyses indicated that the concentration of phenolic endgroups per mole of polymer does not change during the polymerization. The presence of some side reactions is indicated by nitrogen analyses. The relationships between the intrinsic viscosity in chloroform at 25°C and M̄n and M̄w are: log [η] = −3.97 + 0.727 log M̄n and log [n] = −3.56 + 0.624 log M̄w.
Role of dimethyl sulfoxide as a solvent for vinyl polymerization
Authors: Gupta Satyendra Nath , Nandi Uma Sankar 
Published: April 2003

AbstractDimethyl sulfoxide has been used as a solvent in the polymerization of methyl methacrylate and styrene. The chain‐transfer coefficients of the solvent and the values of δ [i.e., (2kt)1/2/kp] in solvent‐monomer mixtures of various compositions were determined. δ was observed to be dependent on the solvent concentration in the case of methyl methacrylate but remained constant in case of styrene. The lowering of the values of δ with increasing solvent concentration in case of methyl methacrylate has been attributed to an interaction between the solvent and poly(methyl methacrylate) radical resulting in lower termination rate.
Chain transfer in ethylene polymerization. V. The effect of temperature
Authors: Mortimer George A. 
Published: April 2003

AbstractIn order to determine the effect of temperature on the chain‐transfer reaction in the free‐radical polymerization of ethylene, chain‐transfer constants were measured for sixteen transfer agents at 130°C and 200°C at 1360 atm. The results were interpreted as ΔE*, the activation energy of the chain‐transfer constant. This value is equal to the difference in activation energy between the transfer step (hydrogen abstraction) and the propagation step (addition to the monomer double bond): ΔE* = Es* − Ep*. Excellent agreement was found between measured ΔE* values determined at 1360 atm pressure and (Es* − Ep*) data for ethyl radical determined in vacuum gas‐phase reactions. Apparently, the ethyl radical is a good model for polyethyl radical. The chain‐transfer constant of ethylbenzene was found to be insensitive to temperature changes, indicating that Ep* = Es* for this compound.
Polymerization of vinyl monomers with salts of bronsted acids
Authors: Yamaguchi Koichi , Minoura Yuji 
Published: April 2003

AbstractThe polymerization of vinyl monomers (N‐phenylmaleimide, acrylamide, acrylonitrile, methyl vinyl ketone, methyl methacrylate, vinyl chloride, and styrene) with sodium salts of Brønsted acids (sodium cyanide, sodium nitrite, sodium hydroxide, etc.) were investigated at 0°C in dimethylformamide. N‐Phenylmaleimide, acrylonitrile, and methyl vinyl ketone were found to undergo polymerization with sodium cyanide, however the other monomers were not polymerized with this salt. In the polymerizations of acrylonitrile and N‐phenylmaleimide with sodium cyanide, the rates of the polymerizations were found to be proportinal to the initiator concentration and to the square of the monomer concentration. The activation energy of acrylonitrile polymerization was 3.7 kcal/mole, and that of N‐phenylmaleimide ws 3.0 kcal/mole. The results of the copolymerization of acrylonitrile with methyl methacrylate at 0°C in dimethyl‐formamide with sodium cyanide confirm that these polymerizations proceeded by an anionic mechanism initiated by the Michael addition reaction of the monomers with the salts. In these polymerizations, the monomer reactivity increased with increase in the e values. The initiation ability of sodium salts increased with increasing pKa of the conjugate acids and with decreasing electronegativity of metal ion in the series of lithium, sodium, and potassium cyanide. The polymerizations took place only in aprotic polar solvents, and did not occur in weak polar solvents and in protonic solvents.
Polymerization of epoxides with dialkylaluminum acetylacetonate catalyst systems
Authors: Kuntz Irving , Kroll W. R. 
Published: April 2003

AbstractCatalyst systems for the polymerization of epichlorohydrin, propylene oxide, and allyl glycidyl ether have been prepared from pure, separately synthesized dialkylaluminum acetylacetonates (R2Alacac). Adding small amounts of water to R2Alacac gives a catalyst system with enhanced activity. An even more active catalyst system for yielding high molecular weight, epichlorohydrin‐containing polymers is obtained when another organometallic compound is added to the R2Alacac‐0.5 water components. The R2Alacac‐0.5 water‐R2Zn system has been studied in detail. Variation in the molar proportion of water and structural changes in the chelate structure of the R2Alacac component have been examined. Results indicate that the bis‐chelate structure, acac(R)‐Al‐O‐Al(R)acac, plays a major role in catalyst formation. A bimetallic catalyst species containing aluminum and zinc atoms is proposed, with zinc functioning primarily in monomer coordianation and with aluminum involved primarily in polymer chain growth.
Polyelectrolyte behavior and macromolecular properties of sodium amylopectin xanthate in dilute solution
Authors: Pramanik A. G. , Choudhury P. K. 
Published: April 2003

AbstractSodium amylopectin xanthate was prepared by xanthation of potato amylopectin in alkaline medium. The pure product was characterized by I2 solution and ultraviolet spectra of the xanthate groups. The polyelectrolyte behavior of Na amylopectin xanthate in aqueous and salt solutions was investigated by viscometry and light scattering. Its polyelectrolyte behavior in aqueous solution as studied viscometrically was completely different from that of Na amylose xanthate, which is characteristic of linear polyelectrolyte molecules. This difference in behavior could be partly due to the branched structure of amylopectin molecule. A dissymmetry study of Na amylopectin xanthate in aqueous and salt solutions, however, showed that Na amylopectin xanthate molecule underwent expansion in water by about 1.3 times its linear dimension in 0.5M NaCl (unperturbed value). Light‐scattering measurements confirmed that the Na amylopectin xanthate molecule had a polydisperse random‐coil chain configuration in 0.25M NaCl. Its molecular weight, end‐to‐end length, and other parameters in salt and alkali solutions were also determined, and the data were then compared with those of Na amylose xanthate in the same media. The solution behavior of Na amylopectin xanthate in 1M NaOH was further investigated and linear expansion factor α, excluded volume factor A2MW/[η], and Flory's hydrodynamic constant φ were evaluated.
Synthetic thermally reversible gel systems. V
Authors: Haas Howard C. , Manning Monis J. , Mach Martin H. 
Published: April 2003

AbstractDifferential thermal analysis has been used to study the fusion of aqueous thermally reversible gels of gelatin and polyacrylylglycinamide (PAG). In the case of gelatin gels, endotherms close to the melting point are readily observed and these are sometimes preceeded by a small exothermic heat of gel reorganization. Calculations are presented to show that breaking of the gelatin gel network requires only a small fraction of the observed endothermic heat of fusion and that most of the heat is required for melting larger crystallites within gelatin aggregates and for perhaps a helix → coil transition. Failure to observe endotherms by DTA over the known temperature range of fusion of PAG gels is consistent with prior measurements and conclusions. The noncrystallinity of PAG gels and soluble aggregates together with a heat of crosslinking of only −5 to −10 kcal/mole of crosslinks places the heat of fusion of PAG gels outside the lower limits of DTA sensitivity.
Influence of torsional stiffness upon temperature response of a polymeric chain
Authors: Majerus John N. 
Published: April 2003

AbstractThe influence of torsional stiffness upon the temperature dependence of the mean square end‐to‐end polymer chain distance 〈r〉 was studied parametrically for six different polymer chain models. The equations for 〈r〉, expressed in terms of the torsional potential energy, were differentiated with respect to temperature and the resulting equations were evaluated numerically. The magnitudes and locations of the secondary barrier heights, angular location and magnitudes of the energy minima, angular location of the maximum barrier U0, spacing of the extrema, and the number of extrema were all found to play a significant role in the value of the predicted thermal expansion coefficients. The coefficients were also found to critically depend upon the relative energy ratio and were usually a highly nonlinear function of this ratio. Transitions between positive and negative values of the thermal expansion coefficients were found to exist and to depend upon the torsional potential shape, energy ratio, and the polymer chain model.
Molecular weight distribution in polyacrylamide prepared by a photochemical method
Authors: Venkatarao K. , Santappa M. 
Published: April 2003

AbstractThe molecular weight distribution of polyacrylamide, prepared by uranyl ion‐photosensitized polymerization of acrylamide in visible light of wavelength 436 mμ, was studied in detail. The polymer was fractionated and the experimental integral and differential distribution curves were drawn. The theoretical distribution function was derived from the kinetics of photopolymerization, assuming the rate constants calculated from previous studies. The theoretical and experimental molecular weight distributions were compared. The results support the mechanism proposed for the photopolymerization reaction.
Kinetics of polymerization of N‐carboxy amino acid anhydride in dimethyl sulfoxide
Authors: Oya Masanao , Uno Keikichi , Iwakura Yoshio 
Published: April 2003

AbstractVarious kinds of NCA's were polymerized in dimethyl sulfoxide (DMSO). DL‐Alanine NCA polymerized at a fast rate without initiator, the rate being represented by Rp1 = k[M]1/2. When the polymerization was carried out in chloroform in the presence of DMSO, the rate was represented by the equation, Rp2 = K2[M][DMSO]1/2.Glycine NCA and DL‐α‐amino‐n‐butyric acid NCA also polymerized at a fast rate in DMSO without initiator. On the other hand, N‐methylglycine NCA, DL‐ and L‐valine NCA and DL‐ and L‐leucine NCA did not polymerize in DMSO without initiator.
Statistical study of the effect of variation of bimolecular rate constant in condensation polymerization
Authors: Nanda V. S. , Jain S. C. 
Published: April 2003

AbstractWe investigate the effect of variation of bimolecular rate constant with chain length on condensation polymerization by a statistical approach. The variation of reactivity with chain length is simulated in the present study by assigning appropriate weight factors to different species. Formal expressions for the size distribution and various averages of interest have been obtained. Some simple cases are then analyzed and comparisons with the experimental results of Taylor and Howard are carried out.
Polybenzopinacols. I. Photolytic coupling of aromatic diketones
Authors: Higgins Jerry , Johannes Arland H. , Jones Joe F. , Schultz Ronald , McCombs D. A. , Menon C. S. 
Published: April 2003

AbstractLow molecular weight polybenzopinacols were obtained by the photolytic coupling of m‐ and p‐dibenzoylbenzene and 4,4′‐dibenzoyldiphenyl ether in isopropanol, tetrahydrofuran–isopropanol, benzene–isopropanol, and benzene–ethanol solutions. The polypinacols were soluble in common organic solvents such as tetrahydrofuran, ether, and benzene. The inherent viscosities ranged from 0.06 to 0.14. Average molecular weight (M̄n) data indicated that the polymers were mostly dimers and trimers.
Copolymers of 1‐methylcyclopropene
Authors: Anderson W. S. 
Published: April 2003

Abstract1‐Methylcyclopropene (MCP) copolymerizes rapidly with acrylic and vinyl monomers to form soluble, high molecular weight products containing enchained cyclopropane rings. The high electron availability in the cyclopropene double bond promotes one‐to‐one alternating copolymerization with sulfur dioxide, maleic anhydride, acrylic acid, acrylonitrile, dialkyl fumarates and acrylic esters. Nonalternating copolymers are obtained with vinyl chloride and vinyl acetate, and attempted copolymerization fails entirely with styrene, α‐methylstyrene and isoprene. This pattern of copolymerization reactivity resembles that of highly compressed ethylene. Methylcyclopropene copolymers have high glass temperatures in spite of the small size of the MCP unit. The combination of high Tg and small size allows preparation of copolymers with high Tg having a wide range of ductilities and cohesive energy densities.
Four‐center type photopolymerization in the solid state. IV. Polymerization of α,α′‐dicyano‐p‐benzenediacrylic acid its derivatives
Authors: Nakanishi Fusae , Hasegawa Masaki 
Published: April 2003

AbstractThe solid‐state photopolymerization of α,α′‐dicyano‐p‐benzene diacrylic acid (p‐CBA) series has been studied. p‐CBA, its esters, amide, and a few other cyano derivatives were prepared and new polymers were obtained from p‐CBA alkyl esters on irradiation of ultraviolet or visible light. Though the polymerization behavior differs with each monomer, polymerization proceeds in essentially the same manner as in the 2,5‐distyrylpyrazine (DSP) and p‐benzenediacrylic acid (BDA) series: the reaction proceeds topochemically forming polymer with a cyclobutane ring in the main chain. Properties of high polymer are typical of cyclobutane‐containing polymer. That is, they are highly crystalline with high melting temperature and a limited solubility. The study on this series of compounds, as well as the DSP and p‐BDA series, supports the generalization that solid‐state dimerization can be extended to solid‐state photopolymerization of compound having two dimerizable units in a molecule.
Characterization and polymerization of thioacetone
Authors: Lipscomb R. D. , Sharkey W. H. 
Published: April 2003

AbstractThe thioketo and thioenol tautomers of thioacetone have been separated by gas chromatography and characterized by infrared and NMR spectra at low temperatures. The pure thioketo tautomer polymerizes rapidly at room temperature, but the thioenol tautomer does not. At room temperature, the thioenol gradually disappears, probably by tautomerization to the reactive thioketo form, which then polymerizes. Attempts to copolymerize thioacetone with vinyl and diene monomers were not successful.
Cyclopolycondensation. XIII. New synthetic route to fully aromatic poly(heterocyclic imides) with alternating repeating units
Authors: Dokoshi Noriaki , Tohyama Shunroku , Fujita Saburo , Kurihara Masaru , Yoda Naoya 
Published: April 2003

AbstractFully aromatic poly(heterocyclic imides) of high molecular weight were prepared by the cyclopolycondensation reactions of aromatic diamines with new monomer adducts prepared by condensing orthodisubstituted aromatic diamines with chloroformyl phthalic anhydrides. The low‐temperature solution polymerization techniques yielded tractable poly(amic acid), which was converted to poly(heterocyclic imides) by heat treatment to effect cyclodehydration at 250–400°C under reduced pressure. In this way, the polyaromatic imideheterocycles such as poly(benzoxazinone imides), poly(benzoxazole imides), poly(benzimidazole imides) and poly(benzothiazole imides) were prepared, which have excellent processability and thermal stability both in nitrogen and in air. The poly(amic acids) are soluble in such organic polar solvents as N,N‐dimethyl‐acetamide, N‐methylpyrrolidone, and dimethyl sulfoxide, and the films can be cast from the polymer solution of poly(amic acids) (ηinh = 0.8–1.8). The film is made tough by being heated in nitrogen or under reduced pressure to effect cyclodehydration at 300–400°C. The polymerization was carried out by first isolating the monomer adducts, followed by polymerization with aromatic diamines. On subsequently being heated, the open‐chain precursor, poly(amic acid), undergoes cyclodehydration along the polymer chain, giving the thermally stable ordered copolymers of the corresponding heterocyclic imide structure.
Halatopolymers
Authors: Economy J. , Mason J. H. , Wohrer L. C. 
Published: April 2003

AbstractThe polymeric character of a series of salts derived from divalent metal ions and organic dibasic acids has been investigated. On melting, these salts form extremely viscous melts which cool to amorphous solids with polymerlike properties and excellent thermal stabilities. This change from a salt to a polymerlike structure appears to be novel and has been termed a halatopolymeric transformation. Halatopolymers are unique in that they have no end groups in the traditional sense. Essentially, the metal carboxylate groups undergo a rapid interchange to afford an association equilibrium of long chains. Studies of the effects of chain modifiers on a calcium sebacate melt at 386°C have indicated that on a time‐average basis the association consists of approximately ten repeat units.
Synthesis and properties of polyamides and polyesters from neocarboranedicarboxylic dichloride
Authors: Korshak V. V. , Bekasova N. I. , Komarova L. G. 
Published: April 2003

AbstractPolyamides and polyesters based on neocarboranedicarboxylie dichloride and previously not described have been prepared by low‐temperature polycondensation in solution and characterized. In preparing the polyamides, the following diamines were used: benzidine, hexamethylenediamine, m‐phenylenediamine, p‐phenylenediamine, 4,4′‐diaminodiphenyl ether, 4,4′‐diaminodiphenylmethane, 4,4′‐diaminodiphenyl sulfide, and hydroquinone diaminodiphenyl ester. Polyesters were obtained by using the following diols: phenolthalein, hydroquinone, 4,4′‐dihydroxydiphenylpropane, 9,9‐dihydroxydiphenylfluorene, 1,6‐hexanediol, and ethylene glycol. The resulting neocarborane polyesters melt and are easily soluble in tetrahydrofuran, amide solvents, and chloroform. The neocarborane polyamides described do not melt, are readily soluble in tetrahydrofuran and dimethylformamide, and form transparent films; they are thermostable in an inert at mosphere at high temperatures.
Stereospecific polymerization of methacrylonitrile. VI. Effect of esters as a complexing agent with diethylmagnesium catalyst
Authors: Joh Yasushi , Kurihara Seiki , Sakurai Toshio , Tomita Tatsunori 
Published: April 2003

AbstractThe stereospecific polymerizations of methacrylonitrile with diethylmagnesium were carefully studied by using various ethers as complexing agents. The complexed ethers exhibit a beneficial effect on the stereoregularity of the resulting polymer, namely, the crystallinity increased by using ethers as a complexing agent. The polymerization rate and the molecular weight of the polymer also increased by using ether‐complexed catalysts. The polymerization behavior was studied with the dioxane–diethylmagnesium complex as a typical complexed catalyst. The behavior was mostly similar to that of the diethymagnesium alone, that is, the rate of the polymerization increased in proportion to monomer concentration, and the solubility index increased with increasing monomer concentration. Interestingly, the viscosity of the acetone‐insoluble fraction increased with increasing monomer concentration, while that of the acetone‐soluble fraction was independent of monomer concentration. This is explained by considering that the catalyst has at least two kinds of catalytic species, one being the species that produces the crystalline polymer by a coordinated anionic polymerization, another being the one from which an amorphous polymer is obtained by a conventional anionic mechanism. The fact that the viscosity of the polymer decreased with increasing the initiator concentration is explained in terms of chain trasfer to the initiator. In case of diethylmagnesium alone, the viscosity of the polymer is independent of the initiator concentration.
Polycondensation of benzyl chloride and its derivatives: A study of the reaction at different temperatures
Authors: Montaudo G. , Finocchiaro P. , Caccamese S. , Bottino F. 
Published: April 2003

AbstractThe polycondensation reactions of benzyl chloride, α‐chloroethylbenzene, and benzhydryl chloride in the presence of SnCl4 or AlCl3 as catalysts have been investigated in the temperature range between +80° and −135°C. Polycondensations of benzyl chloride and α‐chloroethylbenzene are quite similar in the reaction kinetics and are thought to occur by the same displacement mechanism. Polycondensation of benzhydryl chloride, however, seems to involve the formation of benzhydryl carbonium ions. At low temperatures linear polymers tend to be formed, in contrast with branched polymers produced at room temperature. Steric effects are found to play a major role in protecting polymers from branching at lower temperatures.Polybenzyl polymers are found to be less linear than poly(‐α‐methylbenzyl), even when prepared at −135°C.
The vacuum and oxidative pyrolysis of poly‐p‐xylylene
Authors: Jellinek H. H. G. , Lipovac S. N. 
Published: April 2003

AbstractPoly‐p‐xylylene prepared by pyrolysis of di‐p‐xylylene has been degraded under vacuum and in the presence of oxygen as a function of temperature and oxygen pressure. The vacuum pyrolysis is mainly due to “abnormal” structures. Volatiles are initially produced quite slowly, but the reaction accelerates subsequently. Arrhenius equations were derived for various ranges of volatile formation. A mechanism has been formulated consisting of random chain scission followed by depropagation (dimers to pentamers); simulatanously another zip reaction produces hydrogen. The thermal, oxidative degradation has been studied above and below the softening point of the polymer as a function of oxygen pressure. A first‐order reaction of volatile formation due to “abnormal” chain scission is followed by normal chain scission, which is also first order. The postulated mechanism leads initially to hydroperoxide formation. Arrhenius equations for volatile formation are different below and above the softening point. Oxygen consumption also follows a first‐order reaction with an energy of activation of 31.5 kcal/mole.