bluuebunny/crossref_metadata_2025_split huggingface dataset:
Triethylaluminum as a concentration‐dependent coinitiator and chain‐transfer agent of free‐radical polymerization of methyl methacrylate in the presence of benzoquinone
Authors: Grotewold Juan , Hirschler Marcelo M. 
Published: April 2003

AbstractYields in methyl methacrylate (MMA) polymerization as a function of triethylaluminum (TEA) concentration have been determined at a constant benzoquinone (BQ) concentration. The polymerization is negligible at [TEA]/[BQ] concentration ratios smaller than 1, but reaches a maximum yield and then decreases for larger TEA concentrations. Molecular weight measurements show a similar trend, although the maximum is shifted with respect to that corresponding to polymer yield. The existence of two reaction mechanisms is shown by rate measurements at constant initial concentrations. One is a fast reaction, over in a few minutes, which accounts for most of the yield after 30 min reaction time. The other is a slower photoinitiated reaction of the products of the fast reaction. The mechanism proposed is based on a chain‐transfer reaction between the inhibitor radical, formed by the addition of the polymer radical (M·) to BQ and TEA, giving a reactive ethyl radical:

The competition between a pair of reactions of TEA and BQ, i.e., a free‐radical reaction corresponding to the conjugate addition and a molecular reaction leading to the BQ reduction product, is held responsible for the observed yield maximum, since the molecular reaction prevails at larger TEA concentrations. The observed drop in the molecular weight is the result of a chain‐transfer reaction on TEA, i.e., the substitution of an ethyl group by the growing polymer radical.
Organometallic polymers. III. Organometallic modifications of diene polymers
Authors: Gal Alon , Cais Michael , Kohn David H. 
Published: April 2003

AbstractA process for the chemical modification of polybutadienes and natural rubber by various metallocene compounds is described. Soluble products of up to 43% ferrocene content were obtained. The effect of substrate, metallocene, and reaction conditions on the course and extent of substitution was investigated. The glass transition temperature Tg was found to increase considerably with the degree of substitution, e.g., cis‐polybutadiene substituted with ferrocene (18 mole‐%) has a Tg of 30°C, as compared with −91°C for the unsubstituted polymer.
Photoconductive copolymers containing N‐vinylcarbazole
Authors: Chang Daniel M. , Gromelski S. , Rupp R. , Mulvaney J. E. 
Published: April 2003

AbstractThe synthesis of N‐vinylcarbazole (VCbz) copolymers in which electron‐accepting groups are incorporated into the polymer chain is reported. The acceptors were introduced by appropriate reactions of VCbz–vinyl acetate or VCbz–acryloyl chloride copolymers and consisted of 3,5‐dinitrobenzoyl, 2,4‐dinitrophenyl acrylate, β‐2,4‐dinitrophenoxy propionate, and trichlorobenzoquinone units. The copolymer containing the 3,5‐dinitrobenzoyl units required no chloranil as a dopant to be photoconductive, and in fact showed a slightly improved photoresponse relative to conventional poly VCbz doped with external chloranil.
Copolyesters of glycols and bisphenols: Concurrent reactions of a new preparative process
Authors: Riecke E. E. , Hamb F. L. 
Published: April 2003

AbstractA mechanism for the preparation of copolyesters from a preformed polyester, diacid, and bisphenol diacetate in the melt phase is described. Utilizing copoly(ethylene:4,4′‐isopropylidenediphenylene 50:50 2‐methylisophthalate) as a model system, the reaction is shown to proceed through simultaneous cleavage of the preformed polyester by diacid, polymerization by condensation of carboxyl and bisphenol acetate groups, and equilibration through polyester cleavage by carboxyl polymer ends. In this model system, the rates of cleavage and polymerization are competitive, which results in a random sequence distribution early in the reaction.
Thiol/ene photocurable polymers
Authors: Morgan C. R. , Magnotta F. , Ketley A. D. 
Published: April 2003

AbstractThe photosensitized crosslinking of polyenes with polythiols has been demonstrated to be a free‐radical chain reaction whose apparent quantum yield is in the range of 2 × 102–4 × 102 mole/einstein. Initiation occurs by abstraction of a hydrogen atom from the thiol group by the excited n,π* triplet of the ketonic photosensitizer. Kinetic studies of model systems have shown that electron‐donating substituents attached or close to the double bond accelerate the thiol addition while electron‐withdrawing groups decrease the rate. With a given olefin, slight differences in reaction rates are observed depending on the structure of the thiol. Mercaptopropionate esters are more reactive than mercaptoacetates which, in turn, are more reactive than alkane thiols. Cure rates for polyene–polythiol systems are in accord with results found for the model systems. Aromatic carbonyl compounds are the most effective sensitizers for this reaction. To a first approximation, the effectiveness of the sensitizer depends only upon the absorbance. No correlation was found between photoactivity and the triplet energies or lifetimes of the sensitizers.
Nuclear magnetic resonance studies on the mechanism of ring opening in ethylene oxide polymerization
Authors: Matsuzaki Kei , Ito Hiroshi 
Published: April 2003

AbstractIn order to obtain quantitative results on the mechanism of ring‐opening polymerization of ethylene oxide, 13C satellite spectra of dideuterioethylene oxides and their polymers prepared by anionic, cationic, and coordination catalysts were measured with deuterium decoupling and analyzed. The ratios of the threo to erythro polymers were same as those of the cis to trans monomers. Therefore, it is concluded that the ring‐opening polymerizations of ethylene oxide proceed almost entirely with inversion of configuration, confirming the results obtained by the analysis of the infrared spectra of the deuterated polymers by Price, Tadokoro and co‐workers.
Anionic polymerization of 2‐vinylpyridine initiated by symmetrical organomagnesium compounds in tetrahydrofuran
Authors: Soum Alain , Fontanille Michel , Sigwalt Pierre 
Published: April 2003

AbstractAnionic polymerization of 2‐vinylpyridine has been studied, initiated either by dialkyl and diaryl magnesium or by living oligomers in tetrahydrofuran solution at 20°C. Spectrophotometric observations indicate the existence of stable active species with different structures. Kinetic data for propagation and viscosimetric measurements on two‐ended polymers agree with a cyclic structure of living polymers and lead us to the conclusion of the existence of reactive negative “tripleions.”
Synthesis and polymerization of vinylidenesilanes
Authors: Billingham N. C. , Jenkins A. D. , Kronfli E. B. , Walton D. R. M. 
Published: April 2003

AbstractMonomers corresponding to the general formula CH2 = C(X)SiMe3, where × = C6H5, Br, Cl, or CO2H, have been prepared. None of these substances undergoes homopolymerization by any standard technique but copolymerization with styrene, methyl methacrylate, or acrylonitrile under the influence of free radicals proceeds at a low rate.
Block copolymers of poly(m‐phenylene isophthalamide) and poly(ethylene oxide) or polydimethylsiloxane: Synthesis and general characteristics
Authors: Zdrahala Richard J. , Firer Edward M. , Fellers John F. 
Published: April 2003

AbstractThe syntheses of poly(m‐phenylene isophthalamide‐b‐ethylene oxide) and poly(m‐phenylene isophthalamide‐b‐dimethylsiloxane) are reported. The development of synthesis procedures for (AB)n and predominantly triblock ABA and BAB sequences are discussed. Chemical compositions, dilute solution viscosities, and solubility behavior of these systems are also given some consideration. These considerations include the problems that arise in condensing block segments together when phase separation is occurring and developing control of the synthesis procedure to produce block systems of varying compositions.
Photodegradation of cellulose acetate fibers
Authors: Hon Nyok‐Sai 
Published: April 2003

AbstractThe photodegradation of cellulose acetate fibers by ultraviolet light in vacuo at 77°K and at ambient temperature was studied. Three kinds of light sources with different wavelengths between 2353 and 6000 Å were employed. ESR studies at 77°K show that several kinds of free radicals are produced from cellulose diacetate (CDA) and cellulose triacetate (CTA) fibers when irradiated with light of wavelength shorter than 2800 Å. Among these methyl radicals formed decayed within 210 min at 77°K. When the temperature was raised above 77°K, radical transformation occurred at 87°K and most of the free radicals decayed at 193°K, whereas the cellulosic radicals were stable at this and even at higher temperatures. Ultraviolet spectroscopy studies revealed that the main chromophores are the carbonyl function of the acetyl group and acetal groups in the polymer. The photodegradation of the polymers at ambient temperature resulted in the formation of gaseous products (mainly CO, CO2, and CH4), together with the loss of bound acetic acid content and sample weight. Decreases in viscosity and reduction of tensile strength and elongation were also observed in the irradiated samples, revealing that the overt effects of ultraviolet light on cellulose acetate fibers are interpreted in terms of free‐radical reactions ultimately leading to main‐chain and side‐group scissions, unsaturation, and the formation of small molecule fragments. Among these, main‐chain scission took place predominantly in CDA fiber and side‐group scission in CTA fiber. The mechanism of the fundamental photochemical degradation processes of cellulose acetate fibers is elucidated.
Alternating copolymerization of ethylene oxide and sulfur dioxide
Authors: Soga Kazuo , Hattori Iwakazu , Kinoshita Jiro , Ikeda Sakuji 
Published: April 2003

AbstractCopolymerization of ethylene oxide (EO) and sulfur dioxide (SO2) was conducted by using a variety of amines as catalyst. Aromatic tertiary amines such as quinoline and pyridine were found to show the best catalytic property of the various amines, and copolymerization was carried out in the temperature range between 0 and 80°C with the use of quinoline. The copolymerization rate was approximately first‐order in quinoline, EO, and also SO2. The copolymer, was always composed of the two monomers: 1:1 ratio, independent of the initial concentration of the monomers. The copolymer obtained was a transparent viscous material which decomposed at 218°C to afford a considerable amount of ethylene sulfite. Spectroscopic analysis of the copolymer combined with the results of elemental analysis indicates the copolymer to have the structure The polymerizability of ethylene sulfite, which might be considered an intermediate compound in the copolymerization, was also examined at 60°C for 4 hr in the presence of quinoline, and it was found that ethylene sulfite could not be polymerized under these conditions.
Synthesis of optically active poly(2‐phenylvinyl alkyl thioethers) and corresponding monomers
Authors: Kurešević V. , Fleš D. 
Published: April 2003

AbstractCis‐(S)(+)‐2‐phenylvinyl alkyl thioethers having 1‐methylpropyl (I), 2‐methylbutyl (II), and 3‐methylpentyl as alkyl groups, were prepared by condensation of phenylacetylene with sodium thioalcoholates in the presence of sodium ethoxide. Thioethers I, II, and III did not polymerize with radical initiators but could be polymerized cationicaly with BF3·Et2O or SnCl4 in bulk at room temperature to oligomers with molecular weights about 2000. Specific rotations of polymers were compared with those of phenylethyl alkyl thioethers, and it was found that there was no difference in the rotation of polymers having molecular weights up to 2000 and model compounds.
Initiated oxidation of polyenes formed in the thermal degradation of PVC
Authors: Nagy T. T. , Kelen T. , Turcsányi B. , Tüdös F. 
Published: April 2003

AbstractPolyenes formed in the thermal degradation of PVC are readily oxidized in the liquid phase in the presence of a radical initiator. In pure oxygen at a constant rate of initiation, different length polyenes are consumed by a first‐order reaction: the rate of consumption is proportional to the polyene length and to the square root of initiator concentration. Applying the relationships given by the theory of chain reactions, we determined the ratio of the rate constant of chain propagation calculated for one double bond k2 to the square root of the chain‐termination rate constant k4. The value obtained, which is relatively high in comparison to other unsaturated hydrocarbons, reflects very well the high reactivity of polyenes of the degraded PVC sample towards oxidation. Intramolecular chain propagation steps are also likely to play a role in the oxidation of polyenes.
Polymerization induced by electron‐beam irradiation of octadecyl methacrylate in the form of a multilayer or monolayer
Authors: Hatada Motoyoshi , Nishii Masanobu 
Published: April 2003

AbstractIn continuation of the previous series of studies, polymerization of octadecyl methacrylate (ODMA) induced by electron beams has been investigated in a form of its multilayer or monolayer in an attempt to prepare a stable thin polymer film having a regular layer structure. ODMA multilayers were prepared by the Langmuir‐Blodgett technique and irradiated with electron beams from a Van de Graaff accelerator. Multiple reflection infrared spectroscopy and x‐ray diffractometry revealed that the ODMA multilayer was polymerized to give a thin polymer film having a regular layered structure when irradiated in nitrogen atmosphere, but no indication of polymerization was observed when irradiated in air. A preliminary study on the ODMA monolayer at a nitrogen–water interface indicated that the monolayer was polymerized.
Dye‐partition method of analysis of end groups in nonpolar polymers re‐examined: Sulfate end groups in persulfate‐initiated polystyrene
Authors: Banthia Ajit K. , Mandal Broja M. , Palit Santi R. 
Published: April 2003

AbstractSulfate, sulfonate, and isothiouronium salt end groups in polystyrene prepared by using the initiator systems K2S2O8, Na2SO3/Cu+2/O2, FeCl3/thiourea, respectively, have been estimated by the dye partition (extrapolation) method. It was observed that while the persulfate‐initiated polymers analyzed to contain very low amount of sulfate end groups (about 0.05–0.3 per polymer molecule), the other two initiator systems yield polymers with about 2 salt end groups [SO and SC(N+H2)‐NH2, respectively] per polymer molecule. The low amount of sulfate end group in persulfate‐initiated polystyrene is in conformity of the initiation mechanism recently proposed by Ledwith et al. for persulfate‐initiated emulsion polymerization of styrene. This study supports our earlier finding that polymer polarity does not affect the results of end‐group analysis by the dye‐partition technique, contrary to some recent reports which claimed otherwise.
Studies with model membranes. X. Evaluation of the thermodynamically effective fixed charge density and permselectivity of mercuric and cupric iodide parchment‐supported membranes
Authors: Siddiqi Fasih A. , Beg Mohammad N. , Singh Surendra P. 
Published: April 2003

AbstractThermodynamically effective fixed charge densities of mercuric and cupric iodide parchment supported membranes were estimated by methods of Teorell, Meyer, and Sievers; Altug and Hair; and the most recent one of Kobatake and co‐workers based on the thermodynamics of irreversible processes. The two limiting forms of Kobatake's equation for dilute and concentrated ranges gave identical values of charge densities. It is interesting to note that these two values of limiting cases are closer to the Teorell‐Meyer‐Sievers and Altug‐Hair values. The theoretical predictions for membrane potential by the Kobatake equation were borne out quite satisfactorily by experimental results obtained with both the membranes.
A new solvent system for gel‐permeation chromatography of poly(ethylene terephthalate)
Authors: Paschke E. E. , Bidlingmeyer B. A. , Bergmann J. G. 
Published: April 2003

AbstractA new solvent system comprising a mixture of nitrobenzene and tetrachloroethane has been developed for determining the molecular size distribution of poly(ethylene terephthalate) (PET) by gel‐permeation chromatography (GPC). Unlike hot m‐cresol, which until now has been the standard GPC solvent for PET, the nitrobenzene–tetrachloroethane mixture can be used at room temperature and thus minimizes polymer degradation and distribution equilibration. Results with this new system reveal reproducibly discernible differences between PET samples prepared by melt and solid‐state polymerization, differences not previously noted in GPC reports based on the use of m‐cresol.
ESCA study of polymer surfaces treated by plasma
Authors: Yasuda H. , Marsh H. C. , Brandt E. S. , Reilley C. N. 
Published: April 2003

AbstractSurfaces of polymers [polyethylene, polystyrene, poly(ethylene terephthalate), poly(oxymethylene), cellulose acetate, polyacrylonitrile, nylon 6, and polytetrafluoroethylene] treated with argon (inert) and nitrogen (reactive) plasma were examined by ESCA (electron spectroscopy for chemical analysis). Argon plasma treatment generally introduces oxygen functionalities into the polymer surface. Nitrogen treatment generally incorporates nitrogen and oxygen functionalities into the treated surface. The extent of oxygen incorporation is typically less than that produced by argon plasma. When nitrogen and oxygen functional groups are already in a polymer structure, the extent of additional incorporation of these two elements as a result of plasma treatment is very much less than with other polymers. Polymers which contain only one of the elements tend to incorporate the other element to much the same degree as polymers without either element initially present.
Polymer radicals trapped in radical‐initiated polytetrafluoroethylene
Authors: Saika A. , Ohya‐Nishiguchi Hiroaki , Satokawa Takaomi , Ohmori Akira 
Published: April 2003

AbstractThe electron spin resonance (ESR) spectra of polymer radicals found to be trapped in polytetrafluoroethylene (PTFE) polymerized with radical initiators were comparatively examined under various conditions and assigned. They are identified as the primary (propagating) radicals RCF2CF2·, which are transformed to primary peroxy radicals RCF2CF2OO· in the atmosphere. Studies of the rates of polymerization and postpolymerization and ESR measurements indicate that the radical content steadily increases during polymerization. The results are discussed in connection with the mechanism of polymerization of tetrafluoroethylene (TFE) and the unusual thermal stability of these radicals in PTFE prepared with initiator.
Acid‐catalyzed hydroxymethylation of benzamide with formaldehyde
Authors: Sato Kenji , Abe Yoshimoto 
Published: April 2003

AbstractHydroxymethylation of benzamide with formaldehyde was investigated in the pH regions of 0.6–6.7 by use of the sulfite method. Investigation of the dependence of the second‐order rate constant of the hydroxymethylation k on pH revealed that k decreased with increasing acidity from pH 6.7, became approximately constant at pH 4.5–5.5 (minimum rate), and then increased with increasing acidity. The rate equation showing the pH dependence of k was drawn from the reaction mechanism, and theoretical curves denoting this rate equation and the corresponding observed curves were compared. It was found that the hydroxymethylation is a reaction between a molecule of benzamide and the conjugate acid of formaldehyde (methylol cation) in the region below ca. pH 2.5, and the parallel reaction of a molecule of benzamide with methylol cation and a molecule of formaldehyde (HCHO) in the pH region of 2.5–4.0; in the region of ca. pH 4.5–5.5 the reaction is that between a molecule of benzamide and a molecule of formaldehyde, and the reaction in the pH region 5.5–6.7 is a parallel reaction of a molecule of formaldehyde with the conjugate base and a molecule of benzamide.
Polymerization of phenylacetylenes. VI. Chain‐transfer reaction in the polymerizations of phenylacetylene and styrene by WCl6
Authors: Hasegawa Kan‐Ichi , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractChain‐transfer reactions to alkylbenzenes were investigated in the polymerizations of phenylacetylene and styrene by WCl6 in benzene at 30°C. In the polymerization of phenylacetylene, alkylbenzenes did not work as chain‐transfer agents, and further ethyl iodide was not a terminating agent. These findings suggest that the polymerization of phenylacetylene by WCl6 differs from the conventional cationic or anionic mechanisms. On the other hand, the ability of alkylbenzenes as chain‐transfer agents in the polymerization of styrene by WCl6 increased in the following order: toluene < p‐xylene < m‐xylene < o‐xylene. This order is similar to that in the polymerization by SnCl4. These results indicate that the polymerization of styrene by WCl6 proceeds by a conventional cationic mechanism.
Haloaldehyde polymers, VII. Polymerization of chlorodifluoroacetaldehyde
Authors: Yamada B. , Campbell R. W. , Vogl O. 
Published: April 2003

AbstractChlorodifluoroacetaldehyde has been prepared by lithium aluminum hydride reduction of methyl chlorodifluoroacetate. Purified chlorodifluoroacetaldehyde was polymerized to crystalline, insoluble polychlorodifluoroacetaldehyde or to a mixture of amorphous polymer soluble in organic solvents and insoluble polymer, depending on polymerization conditions and type and amount of initiators. The polymer, particularly the soluble fraction, could be end‐capped by acetylation to improve the thermal stability of the initially unstable polymer. The thermal degradation of polymer prepared by various techniques has been studied before and after acetylation and the stability was compared to that of other polyhaloacetaldehydes. Chlorodifluoroacetaldehyde was copolymerized with other haloacetaldehydes and with phenyl isocyanate.
Self‐crosslinkable polymers. IV. Copolymerization of 1‐ethenyl‐4‐(2,3‐epoxy‐1‐propoxy)benzene with vinylpyridines
Authors: Tanaka Yoshio , Minowa Michiko , Kato Masao , Kurihara Yoshie , Sakakibara Yoshiaki 
Published: April 2003

AbstractSoluble and self‐crosslinkable linear copolymers with pendant epoxy and pyridyl groups were obtained from 1‐ethenyl‐4‐(2,3‐epoxy‐1‐propoxy)benzene (M1) and vinylpyridines (M2) by the action of α,α′‐azobisisobutyronitrile. The monomer reactivity ratios were determined in tetrahydrofuran at 60°C (r1, r2, and vinylpyridine given): 0.467, 0.638, 4‐vinylpyridine; 0.556, 1.25, 2‐vinylpyridine; 0.639, 1.38, 5‐ethyl‐2‐vinylpyridine. The Q and e values for 1‐ethenyl‐4‐(2,3‐epoxy‐1‐propoxy)‐benzene were calculated as 1.3–1.6 and −1.1–−1.3, respectively, with the reported Q–e values for these vinylpyridines. The intrinsic viscosities of the copolymers were found to be 0.15–0.30 in tetrahydrofuran at 30°C and to be dependent on the copolymer composition. The copolymers with these vinylpyridines were amorphous, had no clear melting points, and became insoluble crosslinked polymers under heating without further addition of any curing agents.