bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular weight distribution of poly‐N‐vinylcarbazole obtained in catalytic solid‐state polymerization
Authors: Higashimura T. , Matsuda T. , Okamura S. 
Published: April 2003

AbstractThe molecular weight distribution of poly‐N‐vinylcarbazole (PVCar) obtained in solid‐state polymerization with various catalysts or γ‐rays was measured by gel‐permeation chromatography, in order to determine the mechanism of the solid‐state polymerization. In addition, the molecular weight distribution of PVCar obtained in the solution polymerization by the cationic catalyst was also measured. The molecular weight distribution of PVCar obtained in the catalytic solid‐state polymerization was broad and had three peaks, independent of the nature of catalysts, radical and cationic. A large amount of low molecular weight oligomer (probably dimer or trimer) was formed in the catalytic solid‐state polymerization of VCar. The molecular weight distribution of PVCar obtained in the cationic solution polymerization showed only one sharp peak. On the other hand, the molecular weight of PVCar obtained in the radiation‐induced solid‐state polymerization was larger than that obtained in the catalytic solid‐state polymerization, and dimer or trimer was not formed. The molecular weight distribution of PVCar obtained was composed of one sharp peak in the high molecular weight region, and a broad peak in the low molecular weight region, and was extremely different from that of PVCar obtained in the catalytic solid‐state polymerization.
Polymerization and reaction of tetraoxane with various olefins catalyzed by BF3O·(C2H5)2
Authors: Miki T. , Higashimura T. , Okamura S. 
Published: April 2003

AbstractThe copolymerization of tetraoxane with various olefins by BF3·O(C2H5)2 in ethylene dichloride at 30°C has been studied. The gas chromatographic technique was employed for the determination of concentration of each compound. The rate of tetraoxane consumption was decreased by the addition of olefins in the order of; no addition > trans‐stilbene > styrene > 1,1‐diphenylethylene > 2‐chloroethyl vinyl ether > cyclohexene ≥ indene ≥ α‐methylstyrene. The formation of the methanol‐insoluble copolymer of tetraoxane and olefin was not confirmed. However, 4‐methyl‐4‐phenyl‐1,3‐dioxane and 4,4‐diphenyl‐1,3‐dioxane were formed in the reaction of tetraoxane with α‐methylstyrene and 1,1‐diphenylethylene, respectively. 4,4‐Diphenyl‐1,3‐dioxane was identified on the basis of the molecular weight measurement, elemental analysis and NMR and infrared spectroscopy. On the other hand, 1,3‐dioxane derivatives were not formed in the reaction of tetraoxane with α,β‐disubstituted olefins. Monomer composition dependence of the copolymerization of tetraoxane with 1,1‐diphenylethylene or α‐methylstyrene has been studied. The amount of 4,4‐diphenyl‐1,3‐dioxane formed reached a maximum at a monomer composition of 1:1 in the reaction of tetraoxane with 1,1‐diphenylethylene. The formation of cyclic dimer of α‐methylstyrene was suppressed by tetraoxane.
Properties of nylon 6 anionically obtained with NaAl(Lac)4 catalyst and polymerization of ϵ‐caprolactam with NaAl(Lac)3(OEt) catalyst
Authors: Konomi T. , Tani H. 
Published: April 2003

AbstractThe m‐cresol‐insoluble polymer of ϵ‐caprolactam obtained with NaAl(Lac)4 catalyst is converted to a soluble polymer on treatment with dilute (0.1 wt‐%) aqueous hydrochloric acid without any accompanying degradation of polymer chain. Aluminum contained in the polymer was not removed completely by extensive extraction with methanol, regardless of the solubilities of the polymers. This fact suggests the existence of two forms of aluminum in the polymer: one contributes to insolubility of the polymer and the other does not. The polymerization behavior in the case of NaAl(Lac)3(OEt) was somewhat different from that of NaAl(Lac)4 and of NaAl(Lac)3(NHBu). These results are considered to reflect a difference in the stability of the Al‐O, Al‐(Lac), and Al‐N bonds in the catalyst.
Synthesis and characterization of polyiminobenzothiazoles
Authors: Evers Robert C. 
Published: April 2003

AbstractA series of polyiminobenzothiazoles was synthesized by the polymerization of either 2,6‐dichloro‐ or 2,6‐diphenoxybenzobisthiazole with a number of aromatic diamines. A polymer was also obtained from the self‐condensation of either 2‐chloro‐ or 2‐phenoxy‐6‐aminobenzothiazole. The polymers were characterized by their elemental analysis and infrared spectra. Thermogravimetric analysis, differential thermal analysis, and softening under load were used to evaluate their thermal properties. The polymers were found to be light tan to brown powders which showed only slight softening below their decomposition temperatures. Onset of breakdown under thermogravimetric analysis in a nitrogen atmosphere generally occurred at 375–400°C. The polymers were sparingly soluble in organic solvents and had inherent viscosities in the range of 0.11–0.55.
Thermal degradation of nadic methyl anhydride‐cured epoxy novolac
Authors: Gac N. A. , Spokes G. N. , Benson S. W. 
Published: April 2003

AbstractA DEN 438 epoxy novolac–Nadic methyl anhydride‐cured polymer was pyrolyzed in vacuum at temperatures to 800°C. Detailed analyses of the products have yielded information on the mechanism of decomposition. Two thirds of the weight loss of the polymer results in formation of relatively involatile high molecular weight gases. Carbon dioxide evolution indicates that at least 50% of the initial anhydride forms diester groups. The degradation of diester sites yields methylcyclopentadiene that is almost entirely decomposed to carbonaceous char.
Polyamide‐imides
Authors: Terney S. , Keating J. , Zielinski J. , Hakala J. , Sheffer H. 
Published: April 2003

AbstractA novel preparation of polyamide‐imides from diphenylmethane diisocyanate and trimellitic anhydride in N‐methylpyrrolidone is described. Partial substitution of trimellitic anhydride with either maleopimaric acid, terephthalic acid, or by various di‐anhydrides permitted a correlation of structure with solution stability and thermal properties. Heat resistance improved with increasing imide content of the polyamide‐imide. Almost all solutions advanced in viscosity on storage at room temperature. The least stable solutions were those that deviated the most from 50–50 amide‐imide. However, the viscosity changes depended somewhat on the type of modifying ingredient. For example, polyamide‐imides modified by substitution of 10% PMDA (pyromellitic anhydride) or BPDA (benzophenone tetracarboxylic acid dianhydride) were less stable than those modified with 10% (cyclopentanetetracarboxylic acid dianhydride) CPDA or THFDA (tetrahydrofuran‐2,3,4,5‐tetracarboxylic acid dianhydride). The use of excess reagent and of monofunctional chain stopper was investigated as a means of controlling solution stability.
Cationic polymerization of β‐pinene, styrene and α‐methylstyrene
Authors: Pietila Heikki , Sivola Arto , Sheffer Howard 
Published: April 2003

AbstractMolecular weight distributions determined by gel permeation chromatography demonstrate that α‐methylstyrene copolymerizes with both β‐pinene and styrene, forming both bi‐ and terpolymers. The composition of precipitated polymer versus crude polymer, as determined by nuclear magnetic resonance, suggests that β‐pinene and styrene also copolymerize. Extraction of the latter bipolymer of β‐pinene and styrene with acetone gives only a small amount of insoluble β‐pinene homopolymer, confirming that β‐pinene and styrene copolymerize in m‐xylene. GPC analysis shows that each copolymer contains some homopolymer. A comparison of Mn with molecular weight calculated from NMR analysis, assuming chain transfer to solvent, indicates that chain transfer is the predominant method of forming dead polymer. The carbonium ions of the growing chain tend to transfer to solvent with increasing ease in the order β‐pinene, styrene, and α‐methylstyrene.
Preparation of block copolymers by use of peroxide‐terminated prepolymer
Authors: Érdy N. Z. , Ferraro C. F. , Tobolsky A. V. 
Published: April 2003

AbstractBlock copolymers containing poly(tetramethylene oxide) and poly(methyl methacrylate) segments were prepared. A commercially available poly(tetramethylene oxide) terminated with tolylene diisocyanate was capped with tert‐butyl hydroxymethyl peroxide and the resulting prepolymer peroxide was used as a free‐radical initiator of vinyl polymerization. Block copolymers formed in temperature‐programmed vinyl polymerizations possessed improved impact strengths over poly(methyl methacrylate) from 0.35 to 1.18 for a fixed (nonoptimized) block length of poly(tetramethylene oxide).
Some consideration of excluded volume effects in dilute polymer solutions
Authors: Yeh R. , Isihara A. 
Published: April 2003

AbstractA two‐parameter model is proposed to analyze the viscosity of dilute polymer solutions; and critical comments are given on recent articles by Berry and by Norisuye et al. The data seem to follow our theoretical model better than other models. Light‐scattering data are also analyzed. The data indicate that the distribution function of monomers decays as a simple exponential function for large r.
Thermally stable silarylene‐1,3,4‐oxadiazole polymers
Authors: Kovacs Hanna Nagy , Delman Alvin D. , Simms Bernard B. 
Published: April 2003

AbstractThe effects of incorporating a p‐phenylene‐ (or m‐phenylene)‐1,3,4‐oxadiazole fragment into the backbone of poly[1,4‐phenylene(diphenylsilyl)‐1,4‐phenylene‐2,5‐(1,3,4‐oxadiazole)], which was developed by the authors, was investigated. Bis[(p‐carbohydrazidophenyl)]diphenylsilane was copolymerized with dipentachlorophenyl terephthalate or isophthalate to produce the prepolymers poly[N‐(p‐diphenylsilylbenzoyl)‐N′N″‐(terephthaloyl)‐N″′‐(p‐benzoyl)dihydrazide] and poly[N‐(p‐diphenylsilylbenzoyl)‐N′,‐N″‐(isophthaloyl)‐N″′‐p‐(benzoyl) dihydrazide], respectively. The polyhydrazides were converted by thermal dehydration into poly[1,4‐phenylene(diphenylsilyl)‐1,4‐phenylene‐(1,3,4‐oxadiazole‐2,5‐diyl)‐1,4‐phenylene‐2,5‐(1,3,4‐oxadiazole)] and poly[1,4‐phenyl‐ene(diphenylsilyl)‐1,4‐phenylene‐(1,3,4‐oxadiazole‐2,5‐diyl)‐1,3,4‐(oxadiazole)]. The new polymers were soluble in organic solvents. Films cast from these solutions exhibited good adhesion to glass and metal surfaces. Thermal analysis showed that the heat stability of all these polymers was about the same and that they were resistant to decomposition when heated in air to about 400°C. The results also indicated that these polymers were somewhat less heat‐resistant than samples of poly‐[1,4‐phenylene(diphenylsilyl)‐1,4‐phenylene‐2,5‐]1,3,4‐(oxadiazole) synthesized from bis(p‐carbohydrazidophenyl)diphenylsilane and bis‐(p‐carbopentachlorophenoxy‐phenyl)diphenylsilane.
Polymerization by transition metal derivatives. XII. Factors controlling activity and stereospecificity in the 1,4 polymerization of butadiene by monometallic nickel catalysts
Authors: Durand J. P. , Dawans F. , Teyssie Ph. 
Published: April 2003

AbstractIn the course of investigations of polymerization of diolefins by transition metal derivatives, we have synthesized various monometallic nickel coordination catalysts. The complexes were prepared by reacting 2,6,10‐dodecatriene‐1,12‐diyl nickel with protonic acids; they were shown to initiate the stereospecific polymerization of 1,3‐butadiene. The study of these catalysts showed the strong influence of the nature of the counteranion used on the stereospecificity and the polymerization rate. Moreover, by adding various ligands, we were able to modify the behavior of the catalytic systems and to prepare either pure cis‐1,4 or pure trans‐1,4 or cis–trans equibinary polybutadienes, starting from the same complex and keeping a high 1,4 specificity. Some of these modifications were shown to be reversible.
Polytriazolines
Authors: Hergenrother P. M. , Carlson L. A. 
Published: April 2003

AbstractSoluble polytriazolines of relatively high molecular weight (ηinh ∼ 0.6 dl/g) have been prepared by the solution polymerization of 2,6‐pyridinediyl dihydrazidine with three different aromatic dialdehydes. Thermogravimetric analysis of the polytriazolines showed weight losses in air and in nitrogen commencing at 280°C and 400°C, respectively. Several attempts to convert triazoline model compounds to the corresponding 1,2,4‐triazoles and quantitatively to prepare methyl‐substituted triazoline model compounds were unsuccessful.
A uniform site theory of ziegler catalysis
Authors: Buls V. W. , Higgins T. L. 
Published: April 2003

AbstractPolypropylene produced by the TiCl3–diethylaluminum chloride catalyst system was separated into two kinds of polymers, a minor atactic fraction with little or no steric order and a major fraction with a high degree of steric order. Each fraction had a wide molecular weight distribution. The relative amounts, the molecular weights and the molecular weight distributions of the fractions responded differently to changing reaction conditions. This indicates that the fractions are produced by separate catalysts and by different reaction mechanisms. Polymer/catalyst mole ratios from polymerizations at various conditions showed that a least one‐half of the TiCl3 content of a catalyst may become directly involved in the polymerization process. A theory is developed which states that (1) the (unactivated) stereospecific fraction of the catalyst consists of molecules containing eight TiCl3 units which are separated from each other by AlCl3 in solid solution; (2) two chlorine atoms in this molecule are replaced with alkyl groups in the first step of activation; (3) the molecule contains two active sites, one d‐ and the other l‐orienting; (4) the molecules are crystallized in an open structure which has equally reactive sites uniformly spaced; and (5) the AlCl3 component is not an inherent part of the stereospecific catalytic structure but it contributes to high activity by opening the crystal structure.
Analysis of the nonvolatile oxidation products of polypropylene I. Thermal oxidation
Authors: Adams J. H. 
Published: April 2003

AbstractThe nonvolatile products in thermal‐oxidized polypropylene sheet have been quantitatively identified by infrared analysis and chemical reaction. The molecular weight changes with oxidation have been studied by gel‐permeation chromatography. It was determined that there is a functional group at each end of a chain. A general oxidation mechanism scheme for polypropylene is presented. The discovery of γ‐lactone is an indication of the importance of an intramolecular backbiting process. The overall functional group distribution is found to differ from that found in a polyethylene sheet.
A high‐performance fluorocarbon elastomer
Authors: Barney A. L. , Keller W. J. , van Gulick N. M. 
Published: April 2003

AbstractPerfluorinated elastomeric copolymers of tetrafluoroethylene and perfluoro(methyl vinyl ether), containing 20–50 mole‐% of the vinyl ether moiety, were prepared in aqueous emulsion free radical initiated polymerization systems. The two monomers show sufficiently similar relative reactivity ratios to permit the preparation of homogeneous copolymers at high monomer conversions. Detailed properies of a 65/35 (molar) copolymer, including outstanding fluid and chemical resistance, to aqueous media and to nearly all organic and inorganic fluids, excellent thermal and oxidative stability, and very low permeability, are given. Efforts to vulcanize the copolymer to achieve good mechanical properties over a wide temperature range were not particularly successful. Through the incorporation of an unspecified cure site monomer, vulcanizates showing to a large degree the desirable properties of the raw copolymer along with good stress‐strain properties and compression set resistance have been obtained.
Précisions apportées au mécanisme de la polymérisation du chlorure de vinyle par le chlorure de tertiobutyle‐magnésium en milieu tétrahydrofurannique. Etude par résonance magnétique nucléaire
Authors: Tho Pham Quang , Taieb Maurice 
Published: April 2003

AbstractNMR analysis of the low molecular weight poly(vinyl chloride) obtained from polymerizations initiated by t‐BuMgCl in THF solution suggests that all the polymer chains have the structure:
magnified image
Enhanced signal/noise ratio by NMR spectrum accumulation confirms this structure in products of higher molecular weights. Examination of the NMR spectrum of vinyl chloride monomer in THF solution reveals the formation of a monomer–THF complex; it seems that the initiation step of the polymerization is governed by this complexation phenomenon.
Synthetic thermally reversible gel systems. IV
Authors: Haas Howard C. , Macdonald Ruby L. , Schuler Alan N. 
Published: April 2003

AbstractThe polymerization kinetics in water of acrylylglycinamide (AG) initiated by K2S2O8 was studied over the temperature range 40.0 to 60.0°C. Monomer concentration was varied from 7.8 × 10−3 to 31.2 × 10−3M and catalyst from 1.85 × to 11.10 × 10−5M. The rate expression is −d[M]/dt = Rp, = k1.22[K2S2O8]0.5[M]1.22, and the overall empirical rate constant, k1.22 = 1.14 × 1011e−15,800/RT 1.0.72 mole−0.72 min−1. To explain the dependence on monomer, a kinetic scheme which includes a bimolecular reaction (k2) between monomer and initiator is suggested. The simplified expression which describes the initial rate of polymerization is: −d[M]/dt = Rp, = k4(2[I]/k5)1/2[M](k1 + k2[M])1/2, where k1, k2, k4 and k5 are rate constants for S2O8 = decomposition, a bimolecular reaction between monomer and initiator, propagation, and termination, respectively. Individual bimolecular rate constants are expressed in liter/mole‐min. The equation predicts a dependence on monomer concentration between 1.0 and 1.5 with 1.5 being approached a t high monomer concentrations. Plots of RP2/[M]2 versus [M] are linear, as predicted by the postulated reaction route and values for k2 and k4/k51/2 were obtained from the slopes and intercepts of these plots. The temperature dependence of the bimolecular monomer‐initiator reaction is k2 = 5.19 × 1021e−36,000/RT. Instead of the usual behavior, the k4/k51/2 ratio was found to decrease with temperature and the difference of activation energies, (E4 − E5/2), is −1.50 kcal. The temperature dependence of the propagation to square root of the termination rate constant ratio is k4/k51/2 = 6.16e1500/RT. These rather unusual results may be related to the ability of AG polymers in water to form thermally reversible gels; even above the gel melting points, the polymers are considerably aggregated in solution. This would tend to make the bimolecular termination reaction more temperature dependent and also account for the high values (59–69) for the k4/k51/2 ratios. For similar temperatures, the overall rate constants for AG are approximately four times those for acrylamide.
Relationship between the autoacceleration of polymerization rate and conversion in radical polymerization
Authors: Ito Katsukiyo 
Published: April 2003

AbstractBy using a simple treatment for the kinetics of radical polymerization with primary radical termination, the ratio kty/ktx of chain termination rate constant kty at conversion y to that ktx at conversion x and the ratio ktiy/ktix of the primary radical termination rate constant ktiy at conversion y to ktix at conversion x were calculated for the polymerizations of methyl methacrylate and ethyl acrylate in the conversion range 0 to 0.4. kty/ktx and ktiy/ktix were treated by using the following equations based on the variation of conversion:

where g(T,y) is the average fractional free volume of radical chain end at conversion y and absolute temperature and β(T) is a function depending on T, and

where gi(T,y) is the average fractional free volume of primary radical at conversion y and T and βi(T) is a function depending on T. The autoacceleration for the above monomers was successfully interpreted by the above treatment.
Polymerization of aromatic aldehydes. IV. Cationic copolymerization of phthalaldehyde isomers and styrene
Authors: Aso Chuji , Tagami Sanae , Kunitake Toyoki 
Published: April 2003

AbstractCopolymerizations of three phthalaldehyde isomers (M2) with styrene (M1) were carried out in methylene chloride or in toluene with BF3OEt2 catalyst. The monomer reactivity ratios were r1 = 0.77, r2 = 0 for the meta isomer and r1 = 0.60, r2 = 0 for the para isomer. The second aldehyde group of both isomers did not participate in polymerization and acted simply as the electron‐withdrawing group, thus reducing the cationic reactivity of these monomers. Copolymerization behaviors of the ortho isomer (o‐PhA) were quite different between 0°C and −78°C. At −78°C, o‐PhA preferentially polymerized to yield “living” cyclopolymers, until an equilibrium concentration of o‐PhA monomer was reached. Then, styrene propagated from the living terminal rather slowly. The block structure of the copolymer was confirmed by the chemical and spectroscopic means. In the copolymerization at 0°C, the o‐PhA unit in copolymer consisted both of cyclized and uncyclized units. This copolymer seemed to contain short o‐PhA sequences. The variation of the o‐PhA‐St copolymer structure with the polymerization temperature was explained on the basis of whether the polymerization was carried out above or below the ceiling temperature (−43°C) of the homopolymerization of o‐PhA.
Representation of terpolymer kinetics on triangular coordinates
Authors: Cruise D. R. , Lacombe R. G. 
Published: April 2003

AbstractThe ideal steady‐state kinetics of polymer formation from two or more monomeric species can be derived from basic rate equations by using the theory of discrete parameter Markov chains. Advantages are: (1) steady‐state assumptions are not required; and (2) a particularly lucid graphical visulization is possible for the case where there are three monomeric species.
Quinone copolymerization. I. Reactions of p‐chloranil, p‐benzoquinone, and 2,5‐dimethyl‐p‐benzoquinone with vinyl monomers under free‐radical initiation
Authors: Hauser C. F. , Zutty Nathan L. 
Published: April 2003

AbstractThe free‐radical copolymerization reactions of p‐chloranil, p‐benzoquinone, and 2,5‐di‐methyl‐p‐benzoquinone with vinyl monomers were studied. Reactions of p‐chloranil with styrene yielded copolymers of approximately 1:1 composition under a variety of reaction conditions. A copolymer containing a block of 1:1 of styrene:p‐chloranil and a block of polystyrene was prepared. Several styrene‐like monomers copolymerized with p‐chloranil to yield copolymrs possessing considerable amounts of incorporated quinone. p‐Benzoquinone copolymerized with 1,3‐butadiene and 2‐vinyl‐pyridine to yield copolymers of significant molecular weights. Reactions of 2,5‐dimethyl‐p‐benzoquinone with vinyl monomers did not yield any isolable polymeric products.
The reactive intermediate in acetylene polymerization: Results of quantum chemical calculations on charge delocalization and its consequences
Authors: Manassen Joost , Rein Robert 
Published: April 2003

AbstractThe charge delocalization in the conjugated vinyl intermediates, which are assumed to be the reactive intermediates in acetylene polymerization, is calculated, taking into account σ as well as π electrons. Delocalization is shown to exist, but it is of a different kind for cations and anions. In the anion, the σ charge is localized at the reactive center and the π change is displaced into the system. In the cations, the σ charge flows towards the reactive center and the π charge is more or less unaffected. π‐overlap charges between the carbon atoms are much less affected than in the case of the corresponding allyl type anion and cation. The calculated charge delocalizations are compared with the little experimental evidence there is, and possible implications of σ and π delocalizations on reactivity and specificity of reaction are discussed.