bluuebunny/crossref_metadata_2025 huggingface dataset:
Inorganic coordination polymers. XIV. Chromium(III) phosphinate perfluorocarboxylate polymers
Authors: Nannelli Piero , Gillman H. D.
Published: April 2003

A series of polymers, {Cr(OH)(OPRR′O)[OOC(CF2)nCF(CF3)2]}x has been prepared and studied. The polymers with R = R′ = C6H5 are soluble in CCl2FCClF2, whereas those with R = CH3 and R′ = C6H5 and with R = R′ = C8H17 are insoluble in all solvents. Attempts to prepare similar materials without hydroxyl groups gave the polymers {Cr(OH)r(OPRR′O)p[OOC(CF2)nCF(CF3)2]q}x with 0 < r < 1. The latter polymers are much more tractable than the former; however they are also less thermally stable. The perfluoro‐carboxylate groups in these materials can either be chelating or bridging, depending on the other ligands present.
Polymerization of vinyl acetate retarded by 4‐methyl‐2,6‐di‐tert‐butylphenol: Kinetic and ESR studies
Authors: Parnell R. D. , Russell K. E.
Published: April 2003

4‐Methyl‐2,6‐di‐tert‐butylphenol strongly retards the free radical polymerization of vinyl acetate initiated by azobisisobutyronitrile. The chain transfer constant, estimated from rate data, is 0.020 ± 0.004 at 35°C and does not vary significantly with temperature. Molecular weight data lead to transfer constants of 0.023, 0.020, and 0.024 at 35, 45, and 55°C, respectively. A mean kinetic isotope effect of 9.8 ± 1.0 is observed for the phenol deuterated at the OH group, showing that the main attack of poly(vinyl acetate) radicals on the phenol involves hydrogen abstraction from this group. The activation energy for hydrogen abstraction is estimated to be 7.8 kcal/mole, and the rate constant at 50°C is 160 ± 40 1./mole‐sec. The stationary concentration of 4‐methyl‐2,6‐di‐tert‐butylphenoxyl in the polymerization mixture is proportional to the phenol concentration and is independent of the initiator concentration, as shown by electron spin resonance studies. Cross termination of poly(vinyl acetate) and phenoxy radicals occurs to a greater extent than mutual termination of these radicals. The rate constant for cross termination is close to 1 × 108 1./mole‐sec at 50°C; the activation energy for cross termination is 2.9 ± 1.3 kcal/mole.
Photopolymerization of methyl methacrylate with the use of iodine as the photoinitiator
Authors: Ghosh Premamoy , Banerjee Amar Nath
Published: April 2003

Kinetics of photopolymerization of MMA at 40°C with the use of iodine as the photoinitiator was studied. At low range of iodine concentration (< 0.0004M), the rate of polymerization was proportional to square root of iodine concentration and the monomer exponent was 2.5, while at a higher range of iodine concentration, (0.0005–0.002M) the initiator exponent and monomer exponent were zero and 3.6–3.8 (i.e., close to 4), respectively. The chain‐transfer constant of iodine at 40°C was found to be 6.0. Polymerization was found to be largely inhibited in the presence of relatively high concentrations of iodine (> 0.005M) and also in presence of hydroquinone. Kinetic and other data indicate a radical mechanism of polymerization involving complexation of monomer molecules with iodine prior to radical generation, and termination is believed to take place bimolecularly at low iodine concentrations and unimolecularly, involving reaction with iodine, at high iodine concentrations (initiator termination).
Synthesis and characterization of phenylated pyrazino‐benzimidazophenanthroline polymers
Authors: Kovar Robert F. , Arnold F. E.
Published: April 2003

Novel phenylated quinoxaline tetraamines have been prepared and polymerized with 1,4,5,8‐naphthalenetetracarboxylic acid in polyphosphoric acid solution. The resulting BBB‐type polymers with pendant phenyl groups along the polymer backbone are soluble in m‐cresol. The polymers, with inherent viscosities ranging from 0.3 to 0.6 dl/g in sulfuric acid, exhibited thermal stabilities near 500°C under nitrogen and near 400°C in air.
Cationic copolymerization of phenyl propenyl ethers
Authors: Yamamoto Kenji , Higashimura Toshinobu
Published: April 2003

Ring‐substituted phenyl propenyl ethers were found to form homopolymers without any rearrangement by metal halides. Phenyl propenyl ethers were less reactive than the corresponding phenyl vinyl ethers in cationic polymerization. In order to study the electronic effect of a substituent on the reactivity, cis‐p‐Cl,p‐CH3, and p‐CH3O‐phenyl propenyl ethers were copolymerized with phenyl propenyl ether in methylene chloride at −78°C with stannic chloride–trichloroacetic acid, and their 1H‐ and 13C‐NMR spectra were measured. The reaction constant ρ against Hammett σp was −2.1. The cis‐phenyl propenyl ethers were slightly more reactive than the corresponding trans isomers. On the other hand, an o‐methyl group decreased the reactivity of phenyl propenyl ether. The low reactivity of o‐methyl phenyl propenyl ether was attributed to the steric hindrance between the propagating carbocation and the monomer.
Polymers from intermediates obtained from hydrogen cyanide
Authors: MacDonald Robert N. , Cairncross Allan , Sieja J. B. , Sharkey W. H.
Published: April 2003

The recent demonstration of an easy synthesis of diiminosuccinonitrile (DISN) from hydrogen cyanide and cyanogen, the reduction of DISN to diaminomaleonitrile (DAMN), and the use of these compounds to form difunctional heterocycles has made several new polyamide intermediates accessible. The 1‐ and 2‐methyl‐1,2,3‐triazole‐4,5‐dicarbonyl chlorides have been polymerized interfacially to form high‐melting polyamides of good heat stability. Interfacial polymerization of 1‐methylimidazole‐4,5‐dicarbonyl chloride and trans‐2,5‐dimethylpiperazine has given a polyamide that is water‐soluble. The 2,6‐ and 2,3‐pyrazinedicarbonyl chlorides have been similarly converted to high‐melting polyamides. 2,6‐Dicyano‐3,5‐dipiperazinylpyrazine has been prepared from tetracyanopyrazine and piperazine and reacted with toluene diisocyanate to form a strong, stiff polyurea. Polyamides were also made from 2,3‐diaminoquinoxaline, 1,4,5,6‐tetrahydro‐5,6‐dioxo‐2,3‐pyrazinedicarbonitrile, and DAMN.
Organometallic polymers. XXIX. Synthesis and characterization of ferrocene‐containing siloxane polymers from bis(dimethylamino)silane–disilanol condensation
Authors: Patterson William J. , McManus Samuel P. , Pittman Charles U.
Published: April 2003

A new monomer, 1,1′‐bis(dimethylaminodimethylsilyl)ferrocene, was synthesized by two routes and polymerized with three aryl disilanols: dihydroxydiphenylsilane, 1,4‐bis(hydroxydimethylsilyl)benzene, and 4,4′‐bis(hydroxydimethylsilyl)biphenyl, yielding three different polysiloxanes. Melt polymerizations carried out at 1 torr pressure and 100°C resulted in the highest molecular weight polymers. Intramolecular cyclization competed with intermolecular chain extension in polymerization of the bis(aminosilane) with dihydroxydiphenylsilane, resulting in isolation of a bridged derivative, 1,3,5‐trisila‐2,4‐dioxa‐1,1,5,5‐tetramethyl‐3,3‐diphenyl[5]ferrocenophane. Cyclization did not compete significantly during the formation of polymers from this bisaminosilane and the two remaining diols, as evidenced by higher yields and greater molecular weights. These polymers could be cast as tough flexible films, and fibers could be drawn from their melts. TGA and DSC data showed the polymer formed from 1,1′‐bis(dimethylaminodimethylsilyl)ferrocene and 1,4‐bis(hydroxydimethylsilyl)benzene to be at least as thermally stable as an arylene siloxane polymer which differed from the ferrocenylsiloxane structure only in the replacement of the ferrocene moiety with a p‐substituted phenylene linkage. The ferrocene‐containing polymers were generally hydrolytically stable under conditions of refluxing THF–H2O(10 : 1) for 1 hr. The polymer‐forming reaction was found to follow second‐order kinetics, and the specific rate constants for formation of two of the polymers were measured.
Synthesis and characterization of isomeric polyesters based on sebacic acid and hexanediols
Authors: O'Malley James J. , Stauffer Walter J.
Published: April 2003

Isomeric homopolymers and random copolyesters based on sebacic acid and isomeric hexanediols were synthesized by condensation techniques and characterized by NMR, GPC, intrinsic viscosity, and DSC. Among the homopolymers, only the polyester derived from the linear 1,6‐hexanediol was found to be crystalline. Typical melting points were 65–70°C, depending on molecular weight, and a Tg of −62°C was measured on a high molecular weight sample. Other isomeric homopolymers derived from the branched diols 2‐methyl‐2‐ethyl‐1,3‐propanediol and 2,5‐hexanediol were amorphous tacky fluids with glass temperatures of −69 and −66°C, respectively. In the case of the random copolymers, NMR analysis was particularly useful in determining the copolymer composition or the diol isomer ratio. DSC data indicated that all the random copolymers containing the linear 1,6‐diol were crystallizable and their melting points depended on copolymer composition. The heat of fusion per repeat unit of poly(hexamethylene sebacate) was found to be 32 cal/g from measurements of the molecular weight dependence of the melting point.
Copolymerization of acrylonitrile. III. Copolymerization with α‐cyanocinnamamide
Authors: Liebersohn Aharon , Kohn David H.
Published: April 2003

Acrylonitrile was copolymerized in solution with α‐cyanocinnamamide up to low conversions. The conventional scheme of copolymerization fitted this copolymer. The basic properties, such as solubility, viscosity, and thermal behavior, of the copolymer prepared in bulk and in solution were determined.
Cationic polymerization of styrene by acetyl perchlorate: Molecular weight distribution of polystyrene and nature of the propagating species
Authors: Higashimura Toshinobu , Kishiro Osamu
Published: April 2003

To clarify the nature of the propagating species in cationic polymerization of styrene catalyzed by acetyl perchlorate, the molecular weight distribution of the polymer was investigated under various conditions. The molecular weight distribution curve for the polymer obtained in methylene chloride at 0°C showed a double peak phenomenon. This suggests that two or more kinds of propagating species participate simultaneously in the propagation reaction. The weight fraction W(H) of the polymer corresponding to the higher molecular weight peak increased with increasing polarity of the solvent. W(H) decreased when the concentration of the ionic species was increased either by an increase of the catalyst concentration or by the addition of the common salt such as tetra‐n‐butylammonium perchlorate. On the other hand, the position of the peak in the molecular weight distribution curve was independent of polymerization conditions. It was concluded that the higher molecular weight part of the polymer was produced under conditions for conductive to dissociation of the propagating species and the less dissociated propagating species was responsible for the lower molecular weight part of the polymer.
Isothermal crosslinking studies on polyquinoxalines by dynamic mechanical methods
Authors: Augl Joseph M. , Duffy James V. , Wentworth Stanley E.
Published: April 2003

Torsional braid analysis was used to investigate the crosslinking behavior of linear quinoxaline polymers with and without reactive side groups. The kinetic parameter followed was the glass transition temperature during isothermal exposure in an inert atmosphere. With high molecular weight polyamide‐quinoxaline copolymers (PPAQ), an initial decrease in Tg was observed during heat exposure which was followed by a subsequent increase in Tg. This was attributed to simultaneous chain scission and crosslinking reactions. Since the effect of random chain scission on the initial change in Tg of the highest molecular weight polymer samples is much stronger than on low molecular weight analogues, a Tg minimum was observed only on the highest molecular weight polymers. Because of the complexity of the reactions occurring one must consider the activation energies obtained from the Arrhenius plots as “apparent” activation energies. No attempt was made to elucidate the mechanisms of these reactions. It has been shown that isothermal heat exposure of high‐temperature aromatic polymers in an inert atmosphere leads to crosslinking. In general, however, linear polymers that have reactive side groups such as methyl or carboxyphenyl groups along the polymer chain crosslink more rapidly than the analogs without these groups.
New routes for copolymerization of carbon monoxide with styrene or vinyl chloride and photodegradation of these copolymers in solutions
Authors: Kawai Wasaburo , Ichihashi Taichi
Published: April 2003

New routes for copolymerization of carbon monoxide with styrene or vinyl chloride were found by emulsion polymerization (nonionic or ionic emulsifier). These procedures yielded copolymers containing carbonyl groups even at high conversion. These carbonyl‐containing polyketones were photoirradiated in solvent. In carbon monoxide—styrene copolymer of high molecular weight, the viscosity change produced by photoirradiation was especially remarkable, while in carbon monoxide—vinyl chloride copolymer no pronounced change in viscosity was observed, even at high contents of carbonyl group.
Anionic polymerization of 2,2,5,5‐tetramethyl‐1‐oxa‐2,5‐disilacyclopentane
Authors: Suryanarayanan B. , Peace B. W. , Mayhan K. G.
Published: April 2003

In the first of a two‐part series, a study has been made of the anionic polymerization of a five‐membered cyclocarbosiloxane, 2,2,5,5‐tetramethyl‐1‐oxa‐2,5‐disilacyclopentane. The polymerization was initiated by lithium n‐butyldiphenylsilanolate in the presence of tetrahydrofuran. The chemical shifts of the protons of the cyclic monomer and the polymer were found to be different, and therefore the rate of polymerization was obtained in an NMR spectrometer. The effects of varying the concentrations of THF, initiator, and water upon the rate of polymerization and upon the molecular weight and the molecular weight distribution were investigated. At a constant concentration of monomer and initiator, the rate of polymerization increased when the THF concentration was increased. At a constant concentration of monomer and THF the rate of polymerization reached a constant value when the initiator concentration was varied. The molecular weight and the molecular weight distribution were dependent upon the initiator to water ratio, whereas water concentration had little effect on the rate of polymerization. Essentially monodispersed polymers were obtained when the concentration of initiator was in large excess to that of water or vice versa. A bimodal distribution in molecular weight was obtained when the concentration of initiator was approximately equal to that of water. The apparent activation energy of polymerization was 12.7 kcal/mole.
Crystallite orientation effects in the 720/730 cm−1 doublet of transcrystalline polyethylene
Authors: Luongo J. P.
Published: April 2003

Transcrystalline films of polyethylene were studied by polarized infrared spectroscopy with varying angles of incidence. The average orientation of the unit cells in the transcrystalline structure was shown to be such that the a axes were predominantly parallel to the surface of the films, and the b axes were predominantly perpendicular to the surface.
Poly(arylene sulfides) with pendant cyano groups as high‐temperature laminating resins. II
Authors: Haddad Ibrahim , Marvel C. S.
Published: April 2003

Poly(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

Four 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

The 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

High‐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

An 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

A 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

Films 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

1,2,2,2‐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

When 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

N‐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

The 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

Adsorption 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

Methyl 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

Styrene–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

Acrylonitrile (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

Poly(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

Photopolymerization 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

14C‐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

Representative 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

1,5‐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

The 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

Cyclic 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.
Photochemistry of fiber‐forming polymers. I. Acrylonitrile copolymers and fibers containing ketone groups
Authors: Alexandru L. , Guillet J. E.
Published: April 2003

The inclusion of minor amounts of methyl isopropenyl ketone in polyacrylonitrile and its copolymers with methyl acrylate and vinyl acetate causes the polymer to become sensitive to ultraviolet light in the 290–320 nm region. Both films and fibers show decreases in molecular weight on irradiation which are attributable to CC bond scission by the Norrish type II reaction. In addition to bond cleavage, decarbonylation occurs, presumably by a type I radical process which also leads to the formation of ketonitrile groups. Fibers spun from such polymers lose most of their tensile strength and elongation after a few months outdoor exposure to natural sunlight, whereas control samples not containing carbonyl groups will retain their strength for much longer periods. Quantum yields both for chain scission and for carbonyl loss in these systems are estimated to be of the order of 0.005.
Applications of ESCA to polymer chemistry. Part VI. Surface fluorination of polyethylene. Application of ESCA to the examination of structure as a function of depth
Authors: Clark D. T. , Feast W. J. , Musgrave W. K. R. , Ritchie I.
Published: April 2003

Molecular core binding energies have been measured by ESCA for series of surface‐fluorinated high‐density polyethylene films. Detailed analysis of the results shows that the technique can be used to establish a comprehensive picture of the early stages of the surface fluorination process. Both the depth of fluorination, and stoichiometry and molecular structure as a function of depth, in the range 0–50 Å have been established. In addition, minor features such as oxidation, hydration, and hydrocarbon contamination at the surface are clearly revealed. Detailed consideration of the results allows a discussion of the dynamics of the overall fluorination process.
Kinetic study of early stages of heterophase polymerization of vinyl chloride initiated by radiation
Authors: Palma G. , Sebastiani L. , Tavan M. , Carenza M. , Brugnaro S.
Published: April 2003

The kinetics of the radiation‐induced bulk polymerization of vinyl chloride in the early stages was determined in the temperature range of −30 to 50°C and dose rates varying from 0.6 to 17 rad/sec by the dilatometric method. Some runs of polymerization of vinyl chloride added with different percentages of tetrahydrofuran were also carried out. The results were found to agree with those previously obtained with polymerizations carried out to high conversions. The results are discussed on the assumption of a decrease in the extent of swelling of the polymer by monomer with decreasing polymerization temperature. By comparison with the data of other precipitating polymerization systems the possibility of a generalized interpretation for the heterophase polymerization is examined.
Free‐radical polymerization of vinylferrocene. I. Kinetics
Authors: George M. H. , Hayes G. F.
Published: April 2003

The polymerization of vinylferrocene in benzene at 60°C in the presence of 2,2′‐azobisisobutyronitrile has been studied. Densities and apparent densities were determined and rates of polymerization measured dilatometrically. The results show that vinylferrocene does not obey normal vinyl polymerization kinetics. Thus the rate of polymerization is proportional to the mean monomer and mean initiator concentrations both raised to a power of 1.1, and the degree of polymerization is independent of the initiator concentration. The polymerization reaction also has a high overall activation energy of 139 kJ/mole. The unusual kinetics are due to a monomolecular termination of the polyvinylferrocene chain radical which is also intermolecular with respect to the chain radical. Termination occurs by an intramolecular electron transfer reaction from a ferrocene nucleus to the growing chain radical which deactivates the chain radical and produces a polymer molecule containing a high spin Fe (III) complex. The presence of this species has been confirmed by Möussbauer and ESR spectroscopy. The rate constant for termination is between 3 and 60 sec‐1. Intramolecular electron transfer has not been previously observed in vinyl polymerizations. The term “intralectran” is suggested to describe this new type of termination. Vinylferrocene readily undergoes transfer to monomer (with a transfer constant equal to about 8 × 10‐3) and to polymer, but not to benzene.
Molecular weight distribution studies. I. Radiation‐induced polymerization of liquid α‐methylstyrene
Authors: Chawla A. S. , Huang Robert Y. M.
Published: April 2003

The concentration of water in purified and BaO‐dried α‐methylstyrene was found to be 1.1 × 10−4M. The radiation‐induced bulk polymerization of the α‐methylstyrene thus prepared was studied in the temperature range of −20°C to 35°C. The polymerization rate varied as the 0.55 power of the dose rate. The theoretical molecular weights and molecular weight distribution were calculated from a proposed kinetic scheme and these values were then compared with those found experimentally. The agreement between these two was reasonably close, and therefore it was concluded that, from the molecular weight distribution point of view, the proposed kinetic scheme for the cationic polymerization of α‐methylstyrene is an acceptable one. The rate constant for chain transfer to monomer kf changed with temperature and was found to be responsible for the decrease in the molecular weight of the polymer with increase in temperature. kf and kp at 20°C were found to be 0.95 × 104 l./mole‐sec and 0.99 × 106 l./mole‐sec, respectively.
Formation of free radicals in photoirradiated cellulose. I. Effect of wavelength
Authors: Hon Nyok‐Sai
Published: April 2003

Formation of free radicals in photoirradiated cellulose has been studied by means of ESR spectroscopy at 77°K. Three kinds of light sources with different wavelengths between 2500 and 4000 ÅR were employed. No radicals detectable by ESR were recorded when cellulose was irradiated with light of wavelength longer than 3300–3400 ÅR. Hydrogen atoms that generated a doublet spectrum (ΔH = 508 G) were observed when cellulose was irradiated with light longer than 2800 ÅR. Hydrogen atoms and formly radicals that generated doublet spectra with splitting constants of 508 and 129 G, respectively, were observed when irradiated with light shorter than 2800 ÅR. The scission of the polymer chain in cellulose is evident from decrease of the degree of polymerization, and the results of mass spectrometric analysis indicated H2, CO, CO2, and H2O to be the main volatile products of cellulose upon photoirradiation.
Thermal degradation of poly(parabanic acid)
Authors: Luongo J. P. , Schonhorn H.
Published: April 2003

A variety of techniques were used to follow the thermal degradation of a poly(parabanic acid) (PPA‐M). The kinetic data associated with the weight loss as a function of time at elevated temperatures indicates a random initiation process followed by depolymerization. Infrared and mass spectral techniques further confirmed the kinetic data by showing the presence of isocyanate and amide groups in addition to CO, CO2, and nitric oxide gases being evolved. Incipient gelation occurs simultaneously with the formation of the amide. A reverse Hoffman rearrangement mechanism has been proposed which appears to be consistent with the available experimental data.
Monomer‐isomerization polymerization. XIII. Monomer‐isomerization polymerization of 1,4‐cyclohexadiene with Ziegler‐Natta catalyst
Authors: Yousufzai A. H. K. , Endo Kiyoshi , Otsu Takayuki
Published: April 2003

1,4‐Cyclohexadiene underwent monomer‐isomerization polymerization to yield poly(1,3‐cyclohexadiene) with a Ziegler‐Natta catalyst comprising TiCl4–Al(C2H5)3 catalyst with Al/Ti molar ratios of 0.5–3.0 at 60°C for 96 hr. Good yields of polymer were obtained (49.5% yield at Al/Ti = 3.0; [η] = 0.04 dl/g). The infrared and NMR spectra of the polymer were identical to those of poly‐(1,3‐cyclohexadiene), confirming that 1,4‐cyclohexadiene first isomerizes to 1,3‐cyclohexadiene and then homopolymerizes to give poly‐1,3‐cyclohexadiene. 1,3‐Cyclohexadiene polymerized without isomerization easily in the presence of TiCl3–Al(C2H5)3 catalyst at Al/Ti molar ratios of 0.5–3.0 at 60°C for 3 hr (76.3% yield at Al/Ti = 3.0; [η] = 0.06 dl/g).
Reaction of diisocyanates with alcohols. II. Catalyzed reactions
Authors: Anzuino G. , Pirro A. , Rossi G. , Friz L. Polo
Published: April 2003

In a previous work we reported a procedure to calculate rate constants for the primary and secondary reactions (urethane and allophanate formation, respectively) between isocyanate and alcohols. In the present paper the same procedure is applied to the catalyzed reaction, thus defining the selectivity for a series of catalysts.
Preparation of high molecular weight poly(vinylaniline)
Authors: Kotlarchik C. , Minsk L. M.
Published: April 2003

For the first time, we believe, a high molecular weight soluble poly(vinylaniline) has been prepared. This was done by a bead polymerization with exclusion of oxygen. The polymer has little or no color and good stability in solution.