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Dissociation and recombination in solid polymers
Notes on papers published in "Polymer Science", 1979
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shown that smectic, nematic and cholesterol type structures m a y be formed in these polymers. A liquid crystalline structure was found for various comb-like copolymers, which do not have mesogenic groups in each monomer unit. The role of intramolecular interactions of lateral groups and their mobility were described for forming a liquid crystalline structure and the need for a certain macromolecular conformation for forming this structure in films prepared using vaxioua solvents, indicated. Translated by E. SEM:ERE
POLYARYLACETYLENES. STRUCTURE AND PROPERTIES* K. I. SIMIONESCU a n d V. PERCHEK Institute of Macromolecular Chemistry, Iassy, Rumania ~I~HERE are m a n y conflicting views in the literature concerning the structure and
properties of polyarylacetylenes. Based on results in the literature and our own information obtained from an investigation into polypentadeutero phenylacetylerie isomers, we tried to form our point of view concerning this class of polymer. Translated by E. SEMERE
DISSOCIATION AND RECOMBINATION IN SOLID POLYMERSt ZIt. SMETS, ZH. ~TIJST, M. SHMITTS-SMETS a n d A. SOMERS Lcuven University, Belgium
thermal dissociation of labile molecules, which are in the solid state of dissolved in a solid polymer matrix, result in the formation of 'products, which differ in their composition and relative yield from products of reactions taking place in solution. These differences may be due to a restriction o f rotary and diffusion mobility. I f dissociation results in the formation of active particles capable of undergoing thermal or photochemical recombination, reaction kinetics do not conform to the bimolecular mechanism as in the ease of reaction in solution, b u t correspond to a gradual process described b y White, Lebedev PHOTOCHEMICAL a]ld
* Vysokomol. soyed. A21: No. ll, 2652, 1979. t Vysokomol. soyed. A21: No. 11, 2652-2653, 1979.
2934
Notes on papers published in "Polymer Science", 1979
and Butyagin. At the first stage rapid recombination takes place in the "cell", followed by a second, very slow stage, corresponding to diffusion controlled recombination of isolated particles (radicals or monomers). Kinetics of this step-by-step reaction are characterized by three different types of dissociationrecombination equilibrium: a) thermal dissociation and radical recombination of benzopinacol and its derivatives; b) photochemical dissociation of hexaphenyl-1, 2-bisimidazole to triphenylimidazole radicals and recombination; c) photochemical dissociation of substituted anthracene- and benzacridisine dimers and photochemical recombination of monomers. In the second case radical pairs and isolated radicals may be readily determined by EPR. Diffusion coefficients of the radical and "cell" dimensions m a y be calculated by the White kinetic equations. Cell dimensions agree with dimensions determined by Butyagin for the radical decomposition of polymers exposed to ~-radiation. Experiments carried out at different temperatures (above and below the glass temperature) demonstrate the effect of the segmental mobility of polymers and the molar volume of labile molecules. Translated by E. S~.~I~E
RECENT RESULTS OF RADIATION SYNTHESIS AND MODIFICATION OF POLYMERS USED FOR SPECIAL PURPOSES* D. 0. HUMmeL Institute of Physical Chemistry, Cologne University, German Federal Republic
The value of radicals. The value of 1 mole of radicals prepared by various methods is as follows: 0.85 -- from benzoyl peroxide; 5.6--from 60Co and 5.6--using a small proportion of 0.2 MV accelerator. Synthesis. Fluorine containing monomers and their monomer mixtures are among the most interesting systems used for radiation initiated synthesis of polymers with satisfactory thermal, mechanical and chemical properties. A detailed investigation has recently been carried out of a vinyl fluoride-vinylideno fluoride systems used for grafting hydrophilic monomers. Modification. Polyethylene, polypropylene, polyvinylfluoride and polytetrafluoroethylene films were used for grafting butadiene, vinyl chloride and styreno from the gaseous phase. Homopolymerization in the gaseous phase can usually be mihimized. A polyethylene-hexafluoroacetone system is the most interesting system both from theoretical and practical point of view Using this system grafting takes place by a chain mechanism ~nd each branch only contains one too* Vysokomol. soyed. A21: No. 11, 2653-2654, 1979.
2933
shown that smectic, nematic and cholesterol type structures m a y be formed in these polymers. A liquid crystalline structure was found for various comb-like copolymers, which do not have mesogenic groups in each monomer unit. The role of intramolecular interactions of lateral groups and their mobility were described for forming a liquid crystalline structure and the need for a certain macromolecular conformation for forming this structure in films prepared using vaxioua solvents, indicated. Translated by E. SEM:ERE
POLYARYLACETYLENES. STRUCTURE AND PROPERTIES* K. I. SIMIONESCU a n d V. PERCHEK Institute of Macromolecular Chemistry, Iassy, Rumania ~I~HERE are m a n y conflicting views in the literature concerning the structure and
properties of polyarylacetylenes. Based on results in the literature and our own information obtained from an investigation into polypentadeutero phenylacetylerie isomers, we tried to form our point of view concerning this class of polymer. Translated by E. SEMERE
DISSOCIATION AND RECOMBINATION IN SOLID POLYMERSt ZIt. SMETS, ZH. ~TIJST, M. SHMITTS-SMETS a n d A. SOMERS Lcuven University, Belgium
thermal dissociation of labile molecules, which are in the solid state of dissolved in a solid polymer matrix, result in the formation of 'products, which differ in their composition and relative yield from products of reactions taking place in solution. These differences may be due to a restriction o f rotary and diffusion mobility. I f dissociation results in the formation of active particles capable of undergoing thermal or photochemical recombination, reaction kinetics do not conform to the bimolecular mechanism as in the ease of reaction in solution, b u t correspond to a gradual process described b y White, Lebedev PHOTOCHEMICAL a]ld
* Vysokomol. soyed. A21: No. ll, 2652, 1979. t Vysokomol. soyed. A21: No. 11, 2652-2653, 1979.
2934
Notes on papers published in "Polymer Science", 1979
and Butyagin. At the first stage rapid recombination takes place in the "cell", followed by a second, very slow stage, corresponding to diffusion controlled recombination of isolated particles (radicals or monomers). Kinetics of this step-by-step reaction are characterized by three different types of dissociationrecombination equilibrium: a) thermal dissociation and radical recombination of benzopinacol and its derivatives; b) photochemical dissociation of hexaphenyl-1, 2-bisimidazole to triphenylimidazole radicals and recombination; c) photochemical dissociation of substituted anthracene- and benzacridisine dimers and photochemical recombination of monomers. In the second case radical pairs and isolated radicals may be readily determined by EPR. Diffusion coefficients of the radical and "cell" dimensions m a y be calculated by the White kinetic equations. Cell dimensions agree with dimensions determined by Butyagin for the radical decomposition of polymers exposed to ~-radiation. Experiments carried out at different temperatures (above and below the glass temperature) demonstrate the effect of the segmental mobility of polymers and the molar volume of labile molecules. Translated by E. S~.~I~E
RECENT RESULTS OF RADIATION SYNTHESIS AND MODIFICATION OF POLYMERS USED FOR SPECIAL PURPOSES* D. 0. HUMmeL Institute of Physical Chemistry, Cologne University, German Federal Republic
The value of radicals. The value of 1 mole of radicals prepared by various methods is as follows: 0.85 -- from benzoyl peroxide; 5.6--from 60Co and 5.6--using a small proportion of 0.2 MV accelerator. Synthesis. Fluorine containing monomers and their monomer mixtures are among the most interesting systems used for radiation initiated synthesis of polymers with satisfactory thermal, mechanical and chemical properties. A detailed investigation has recently been carried out of a vinyl fluoride-vinylideno fluoride systems used for grafting hydrophilic monomers. Modification. Polyethylene, polypropylene, polyvinylfluoride and polytetrafluoroethylene films were used for grafting butadiene, vinyl chloride and styreno from the gaseous phase. Homopolymerization in the gaseous phase can usually be mihimized. A polyethylene-hexafluoroacetone system is the most interesting system both from theoretical and practical point of view Using this system grafting takes place by a chain mechanism ~nd each branch only contains one too* Vysokomol. soyed. A21: No. 11, 2653-2654, 1979.