bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(arylene sulfides) with pendant cyano groups as high‐temperature laminating resins. II
Authors: Haddad Ibrahim , Marvel C. S. 
Published: April 2003

AbstractPoly(phenylene sulfides) containing various amounts of pendant cyano groups were synthesized from m‐benzenedithiol and the corresponding amounts of p‐dibromobenzene and 3,5‐dichlorobenzonitrile. The polymers prepared by the use of 10, 15, 20, and 25% of the nitrile‐containing dichloro compound were slightly off‐white with melting ranges below 100°C and had inherent viscosities of about 0.15 dl/g in hexamethylphosphoric triamide at 30°C. The polymers prepared from m‐benzenedithiol and the stoichiometric amounts of 2,4‐dichlorobenzonitrile or 3,5‐dichlorobenzonitrile looked similar to those described above, yet they possessed much higher melting ranges. The poly(phenylene sulfide) prepared by the use of 2,4‐dichlorobenzonitrile had an inherent viscosity of 0.06 dl/g while the polymer prepared from the 3,5‐dichloro isomer had an inherent viscosity of 0.38 dl/g. All the polymers listed above were crosslinked by heating alone or in the presence of anthracene‐9,10‐bisnitrile oxide to give black resinous polymers that were insoluble in hexamethylphosphoric triamide in which the original polymers dissolved quite readily.
Synthesis of polyperfluoroalkylenetriazines
Authors: Grindahl George A. , Greenwald John R. , Troporcer Louis H. , Pierce Ogden R. , Kim Yung K. 
Published: April 2003

AbstractFour new s‐triazine polymers were prepared by the mercury‐induced coupling of bromodifluoromethyl‐substituted ditriazinyl‐perfluoroalkane derivatives. Each polymer was composed of CF3‐substituted s‐triazin rings alternately joined with CF2CF2segments and \documentclass{article}\pagestyle{empty}\begin{document}$\hbox{---}\hskip-5pt({\rm CF}_2 )_8 \hbox{---}$\end{document}, a mixture of (CF3CFO(CF2)5OCF(CF3) and (CF3)CFOCF2CF(CF3)OCF2)4, CF2OCF2, or CF2SCF2, segments. All polymers were elastomeric and displayed high temperature stability on thermogravimetric analysis. The polymers containing either CF2OCF2 or CF2SCF2 segments showed high temperature limits slightly lower than the other two systems.
Radiation‐induced heterogeneous polymerization of methyl methacrylate in precipitants
Authors: Wada Takeshi , Takehisa Masaaki , Machi Sueo 
Published: April 2003

AbstractThe radiation‐induced heterogeneous polymerization of methyl methacrylate in various precipitants, mainly methyl alcohol, was carried out, and the effects of reaction conditions on the polymerization behavior and the molecular weight distribution of polymer were studied. Bimodal molecular weight distributions were found for the polymer produced by the heterogeneous polymerizations in methyl alcohol and in tert‐butyl alcohol. The apparent activation energy is 1.0 and 4.5 kcal/mole, respectively, for the polymerization at a monomer concentration of 10 vol‐% in methyl alcohol above and below 35°C. The polymerization at a monomer concentration lower than 40 vol‐% in methyl alcohol proceeded with the precipitation of polymer. The dose rate exponent of the mean rate of heterogeneous polymerization decreased from 0.5 to a smaller value as the polymerization progressed. The ratio of the two peaks in the bimodal molecular weight distributions of polymer produced in methyl alcohol was affected by the reaction conditions. These results show the coexistence in the polymerizations of two different physical states of propagating chain, a loose state and a rigid one. The reaction scheme is discussed in connection with the physical factors which affect the solubility or the mobility of propagating chains, and the rate of elementary reactions, which influences the degree of propagating chains.
Chlorine distribution and structure–property relationship of chlorinated polypropylene
Authors: Mitani Katsuo , Ogata Takayuki , Iwasaki Masatoshi 
Published: April 2003

AbstractHigh‐resolution proton magnetic resonance (PMR) spectroscopy was used to determine the chlorine distribution of chlorinated polypropylenes in 1,1,2,2,‐tetrachloroethane solution and suspension (5–25 wt % chlorine). The determination is based on measuring the relative amounts of methyl and methylene groups which are α, β, and γ to chlorinecontaining groups in chlorinated polypropylenes. The results obtained from the 100 MHz and 220 MHz PMR spectrometers were compared with the theoretical predictions provided by Frendsdorff and Ekiner, based on the statistics of substitution polymers. Furthermore, the PMR data were correlated with infrared and differential scanning calorimetry data to obtain the structural and crystalline properties. The comparison showed that the suspension‐chlorinated polypropylenes show structure heterogeneity and thermal instability, whereas polymers chlorinated in solution with gaseous chlorine show a random chlorine distribution and thermal stability compared with the former.
300 MHz 1H‐NMR study of poly(propylene sulfide)
Authors: Sepulchre Maurice , Spassky Nicolas , Van Ooteghem Daniel , Goethals Eric J. 
Published: April 2003

AbstractAn 1H 300‐MHz NMR spectroscopic study of deuterated poly(propylene sulfide) shows that methylene protons are sensitive to triad effects. It was possible to distinguish i, hi, s, and hs triads. Experimental values found for different polymers are in good agreement with theoretical amounts obtained from statistical probability calculation. The methyl groups are also slightly stereosensitive. By using optically active deuterated monomers with different R/S ratios it was possible to confirm the assignment of peaks and the tacticity. Nondeuterated polymers give very complicated spectra, and only the highly stereoregular polymer could be analyzed through its ABCX3 spin system.
Polyphenylquinoxalines with high glass transition temperatures via highly fused aromatic tetraamines
Authors: Hedberg F. L. , Arnold F. E. , Kovar R. F. 
Published: April 2003

AbstractA series of polyphenylquinoxalines has been synthesized by the reaction of p,p′‐oxydibenzil with aromatic tetraamines containing varying numbers of fused rings. It was found that the glass transition temperatures of the resultant polymers increased as the the number of adjacent fused rings in the polymers was increased. This provided the basis for achieving glass transition temperatures for the polymers in excess of 400°C, substantially higher than the state‐of‐the art polyphenylquinoxalines. All of the polymers displayed both the good thermal stability and the solubility in m‐cresol characteristic of the polyphenylquinoxaline family of polymers.
Photosensitized dehydrochlorination of poly(vinyl chloride). III. Reaction of thermally degraded poly(vinyl chloride) with hydrogen chloride
Authors: Owen Eryl D. , Williams John I. 
Published: April 2003

AbstractFilms prepared from thermally degraded poly(vinyl chloride) were photolyzed in the presence of hydrogen chloride. When the light was filtered through a Pyrex disk, the absorbance in the region between 270 nm and about 415 nm decreased and reached a minimum value but the absorbance increased at wavelengths shorter than 270 nm and longer than 415 nm. Maximum bleaching occurred at a wavelength which depended on that of the irradiating light. When the Pyrex filter was omitted, an additional slower photodehydrochlorination reaction was superimposed on the photobleaching reaction. Photolysis of hexane or ethanol solutions of 1,8‐diphenyloctatetra‐1,3,5,7‐ene and hydrogen chloride showed a similar reaction involving bleaching of the absorption of the polyene structure. The problems of using absorbance as an indication of the extent of the photodegradation of poly(vinyl chloride) are discussed.
Preparation and properties of 1,2,2,2‐tetrachloroethyl esters of β‐vinylacrylic, fumaric, and muconic acids and their homopolymers or copolymers
Authors: Bezděk M. , Bouchal K. , Lokaj J. , Pivcová H. , Hrabák F. 
Published: April 2003

Abstract1,2,2,2‐Tetrachloroethyl esters of β‐vinylacrylic, muconic, and fumaric acids were prepared by the addition reaction of chloral with pentadienoyl chloride, hexadienedioyl chloride, and fumaroyl chloride in the presence of FeCl3. The homopolymer of the first and copolymers of the other esters with styrene were obtained by radical polymerization. The basic chemical and physical characteristics of the compounds prepared were determined, and the assumed structure was confirmed by the infrared, NMR, and mass spectra.
Kinetic analysis based on the excluded‐volume effect for radical polymerization
Authors: Ito Katsukiyo 
Published: April 2003

AbstractWhen the potential of average force based on the excluded volume affects the relative motions of the polymer radicals, the specific rate for bimolecular reaction between them can be approximated as kt = const. (ns)−a, where a = 0.153(2b − 1), b being a constant in the Mark‐Houwink equation, and n and s being degrees of polymerization. Introduction of such a rate into kinetic equation yields a relative molecular weight distribution: G(n) = (n/m)2–2a exp {ph(m1–a − n1–a)}, where m = (2/ph)1/(1–a) is a degree of polymerization for the maximum in G(n) and ph is a parameter denoting kinetic character. Further, the relationship between polymerization rate Rp, monomer concentration [M], and initiator concentration [ε] is found to be:

where σ is a parameter denoting primary radical termination and η and η⊖ are viscosities for an arbitrary solvent and ⊖‐solvent, respectively. These relationships are sufficiently applicable to the data obtained in the polymerizations of styrene and methyl methacrylate.
Mechanism of charge‐transfer polymerization. XI. Radical copolymerization of N‐vinylindole with electron‐accepting monomers
Authors: Oshiro Yasuo , Shirota Yasuhiko , Mikawa Hiroshi 
Published: April 2003

AbstractN‐Vinylindole (NVI) was copolymerized with such electron‐accepting monomers as fumaronitrile (FN) or diethyl fumarate (DEF) under initiation with a radical catalyst. The compositions of the copolymers varied from 1:1.1 to 1:1.85 (NVI:FN or DEF). The FN or DEF content in the copolymer increased with increase in the molar fraction of the FN or DEF monomer in the monomer feed. It was suggested that both copolymers have a 1:1 recurring unit of NVI and the electron‐accepting monomer, thus being alternating copolymers, and that further addition of the electron‐accepting monomer to the indole ring occurred at its electron‐rich β‐carbon atom.
Kinetics of free‐radical copolymerization of α‐methylstyrene and styrene
Authors: Rudin Alfred , Chiang S. S. M. 
Published: April 2003

AbstractThe free‐radical copolymerization of α‐methylstyrene and styrene has been studied in toluene and dimethyl phthalate solutions at 60°C. Gas chromatography was used to monitor the rate of consumption of monomers. For styrene alone, the measured rate of polymerization Rp and M̄n of the polymer coincided with values expected from previous studies by other workers. Solution viscosity η affected Rp and M̄n of styrene homopolymers and copolymers as expected on the basis of an inverse proportionality between η1/2 and termination rate. The rate of initiation by azobisisobutyronitrile appears to be independent of monomer feed composition in this system. Molecular weights of copolymers can be accounted for by considering combinative termination only. The effects of radical chain transfer are not significant.A theory is proposed in which the rate of termination of copolymer radicals is derived statistically from an ideal free‐radical polymerization model. This simple theory accounts quantitatively for Rp and M̄n data reported here and for the results of other workers who have favored more complicated reaction models because of the apparent failure of simple copolymer reactivity ratios to predict polymer composition. This deficiency results from systematic losses of low molecular weight copolymer species in some analyses. Copolymer reactivity ratios derived with the assumption of a simple copolymer model and based on rates of monomer loss can be used to predict Rp values measured in other laboratories without necessity for consideration of depropagation or penultimate unit effects. The 60°C rate constants for propagation and termination in styrene homopolymerization were taken to be 176 and 2.7 × 107 mole/l.‐sec, respectively. The corresponding figures for α‐methylstyrene are 26 and 8.1 × 108 mole/l.‐sec. These constants account for the sluggish copolymerization behavior of the latter monomer and the low molecular weights of its copolymers. The simple reaction scheme proposed here suggests that high molecular weight styrene–α‐methylstyrene copolymers can be produced at reasonable rates at 60°C by emulsion polymerization. This is shown to be the case.
Isotopic exchange of gaseous ammonia 14NH3 and 15NH3 in sulfonated macroreticular ion exchangers
Authors: Prokop Z. , Setíanek K. 
Published: April 2003

AbstractAdsorption and 15NH3 isotopic exchange was performed on dry macroreticular polystyrene ion exchanges crosslinked with varying amounts of divinylbenzene and partially neutralized by 14NH3. Data on pressure changes and mass spectrometric analyses of isotopic composition of the gaseous phase were used to calculate equilibrium distribution of 14NH3 and 15NH3 under various dislocation conditions. It was established that along with the exchange of 14NH3 to a gaseous phase, 15NH3 penetrates to the mass of ion exchanger. This is evidently due to the migration of ammonia among functional groups. It was found that by thermal desorption under reduced pressure ammonia is released only from functional groups located on the surface of ion exchanger.
Relationship between radical polymerization rate and initiator concentration in various solvents
Authors: Ito Katsukiyo 
Published: April 2003

AbstractMethyl methacrylate and styrene were polymerized by using 2,2′‐azobis(2,4‐dimethyl valeronitrile) as initiator in various solvents. When a poor solvent is used, the dependence of polymerization rate Rp on initiator concentration [C] is small and can be treated by equations for the analysis of the polymerization with primary radical termination. With a good solvent, the dependence of Rp on [C] is so large that such equations are not applicable. Thus, the [C] dependence in a good solvent is explained qualitatively through the molecular weight dependence of rate for termination between polymer radicals, based on the excluded volume effect.
Conductivity of carbon black‐loaded styrene–butadiene rubber
Authors: Amin M. , Hassan H. H. , Abdel‐Bary E. M. 
Published: April 2003

AbstractStyrene–butadiene rubber (SBR) charged with 50 phr of HAF carbon black has been found to show a positive temperature coefficient of resistivity close to 0.07/°C at 27°C. Beyond a point (75°C) of minimum conductivity, however, it behaves as a normal noncrystalline semiconductor with a resistivity which decreases with rise of temperature with an activation energy of 0.56 eV. Blending the composition with poly(vinyl chloride) (PVC) shifts the minimum towards lower temperatures. The descending branch of the conductivity versus reciprocal absolute temperature characteristic is probably associated with thermal expansion of tunnelling paths separating the conducting carbon particles.
Cationic starch–polyacrylonitrile graft copolymer latexes
Authors: Gugliemelli L. A. , Swanson C. L. , Baker F. L. , Doane W. M. , Russell C. R. 
Published: April 2003

AbstractAcrylonitrile (AN) was graft‐polymerized onto gelatinized cationic starch (CS) possessing diethylaminoethyl ether groups by cerium (IV) initiation to give stable latexlike copolymer dispersions. Dispersions of the latex copolymers, having up to 50% grafted polyacrylonitrile (PAN), air‐ and heat‐dry on glass to clear, adhesive films. Sonification of up to 8% dispersions at 20 Khz reduced their viscosities from 1500–3000 cP to 15–40 cP. Scanning electron microscopy revealed that both nonsonified and sonified dispersions consist of ball‐like particles measuring about 0.05–0.15 μ in diameter when dry. The films are formed by coalescence of these particles. The degree to which AN grafts onto CS at ambient temperature is related to the nitrogen content of CS, gelatinization time of CS at 95°C, sequence of AN and cerium(IV) addition, concentration of cerium (IV), concentration of AN, and severity of reaction agitation. Number‐average molecular weight values of PAN were about 106 when grafting was conducted under stirring and about 5 × 105 when conducted under shaking action.
Viscosity–molecular weight relationship for fractionated poly(ethylene terephthalate)
Authors: Hergenrother William L. , Nelson Charles Jay 
Published: April 2003

AbstractPoly(ethylene terephthalate) was separated into 12 fractions of equal size by a stepwise increase in the amount of solvent in the two‐phase liquid fractionation system of phenol‐tetrachloroethane (PTCE) (1:1) and n‐heptane. Various molecular weight parameters of the fractions were measured by osmotic pressure and gel‐permeation chromatography. Intrinsic viscosity‐molecular weight plots were made for three different solvents at 25°C. Mark‐Houwink constants for viscosity‐average molecular weight were measured and gave values of K of 2.50, 2.37, and 2.25 × 10−4 dl/g and values of a of 0.73 for 1:1 PTCE, 3:2 PTCE, and o‐chlorophenol, respectively. A comparison with the literature values for this polyester was made, and application of the Mark‐Houwink equation to the determination of number‐average (Mn) and weight‐average (Mw) molecular weight of whole polymers is considered.
Photopolymerization of vinyl monomers with quaternary ammonium salts
Authors: Ko Munam , Sato Tsuneyuki , Otsu Takayuki 
Published: April 2003

AbstractPhotopolymerization of vinyl monomers with a series of quaternary ammonium salts has been investigated. However, quaternary ammonium salts used are not photosensitizers but rather photoinitiators. The salts photoinitiation activity was observed to vary widely with the counteranion in quaternary salts used and also with the alkyl group in their amine components. In general, the halide salts were more effective than tetrafluoroborate salts. It was also found that the overall activation energy for the photopolymerization of methyl methacrylate with dimethylbenzylanilinium tetrafluoroborate was 5.9 kcal/mole, and its rate was proportional to the 0.32 and 1.0 order of the concentration of the salt and the monomer used, respectively. An endgroup similar to dimethylaniline was found to be present in the methyl methacrylate polymer obtained by above system; this is probably a methylanilinomethyl group, from the characteristics of its ultraviolet spectrum.
Radiochemical studies of free‐radical vinyl polymerizations. VI. Polymerization of methyl methacrylate in the presence of organotin PVC stabilizers
Authors: Ayrey G. , Head B. C. , Poller R. C. 
Published: April 2003

Abstract14C‐Azoisobutyronitrile was used to initiate polymerizations of methyl methacrylate in the presence of the organotin compounds: tetrabutyltin, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin di(ethyl mercaptide), dibutyltin di(dodecyl mercaptide), and dibutyltin dichloride. Only dibutyltin dichloride affected rates of polymerization significantly, and this was ascribed to an increase in the velocity constant kp for the propogation reaction. No evidence was obtained for radical displacement reactions of the polymer radicals with bonds between tin and carbon, oxygen, sulfur, or chlorine. Transfer activity exhibited by the mercaptides was ascribed to traces of thiol impurity, possibly formed during storage. The relevance of these results to the mechanism of stabilization of poly(vinyl chloride) is briefly discussed.
Thermal degradation of polyurethanes by hexamethyldisilazane: Syntheses of polyhexamethyleneurea with organosilicon reagents
Authors: DiSalvo Anthony L. , Cornell John H. 
Published: April 2003

AbstractRepresentative aliphatic and aromatic polyurethanes undergo degradation upon treatment with hexamethyldisilazane (HMDS) at elevated temperatures. The course of the reaction is dependent on the nature of the polyurethane. Thus heating poly‐[ethylene methylene bis(4‐phenylcarbamate)] with HMDS in a sealed tube at 197°C gives high yields of 4,4′‐diaminodiphenylmethane, trimethylisocyanatosilane, and 1,2‐bis(trimethylsiloxyethane) along with lesser amounts of hexamethyldisiloxane, bis‐(trimethylsilyl)carbodiimide, and ammonia. Under the same conditions, poly(ethylene N,N′‐hexamethylenedicarboxylate) gives no diamine, but good yields of polyhexamethyleneurea and 1,2‐bis(trimethylsiloxy)ethane together with smaller quantities of the other named products are obtained. In the course of this study, two novel routes to polyalkyleneureas were developed. For example, polyhexamethyleneurea is obtained in good yield by treatment of 1,6‐hexanediamine with trimethyklisocyanatosilane at elevated temperatures in a sealed tube. The reaction of 1,1′‐hexamethylenediurea with HMDS under these conditions results in formation of the same product. A mechanism rationalizing the foregoing results is proposed which involves initial nucleophilic attack by HMDS on the polyurethane to give an intermediate disilylated urea. Thermal decomposition of this intermediate by alternative routes would give the observed products.
Polyimides derived from cyclooctadiene dianhydrides
Authors: Dror Michael , Levy Moshe 
Published: April 2003

Abstract1,5‐Cyclooctadiene‐1,2,5,6‐tetracarboxylic dianhydride reacts with diamines in m‐cresol at 110°C to give high molecular weight polymides soluble in m‐cresol and tetrachloroethane. Films can be cast from solution and fibers drawn by dry and wet spinning. These polyimides showed rather low thermal stability, but high hydrolytic stability and good mechanical properties. The polyamic acid intermediates cannot be isolated due to spontaneous cyclization even at room temperature. This is discussed in terms of the strain in the cyclooctadiene ring.
Photochemistry of nonconjugated bichromophoric systems: Photoreductive polyrecombination of diaryl ketones
Authors: De Schryver F. C. , Thien Tran V. , Toppet S. , Smets G. 
Published: April 2003

AbstractThe irradiation of nonconjugated bichromophoric systems, diaryl ketones, with ultraviolet light in the presence of hydrogen donors, such as isopropanol or bisbenzhydrol, yields high polymers. Two series of arylketones were investigated, namely bisbenzophenones and bisketotriazoles. The cage reaction, which arises from the cross combination between the acetone ketyl and bisbenzophenone ketyl radicals, was estimated to be very small but may constitute a chain termination reaction in the photopolymerization in isopropanol. The photopolymerization of bisdiketone–dihydrol systems was found to yield polymers with much higher molecular weights than those obtained from the photopolymerization of bisdiketone–isopropanol systems. The photolysis of some binary mixtures of aromatic diketones in the presence of isopropanol yielded statistical copolypinacols. In some favorable cases, the NMR spectrum of the copolymer obtained showed three distinct linkages and from the infrared spectrum intensities the copolymers composition and the number average length of the sequences may be determined.
Cyclic crack propagation and molecular kinetics of polymers
Authors: Radon J. C. 
Published: April 2003

AbstractCyclic tests in tension were performed on PMMA and PC center‐notched plate specimens. Frequencies between 0.1 and 100 Hz at temperatures from −78 to +55°C were investigated. Correlations between crack growth rates, described in the terms of stress intensity K, and the appropriate values of the loss factor tan δ were studied. It was concluded that, in the investigated conditions, a direct correspondence exists between the crack growth rate and tan δ.