Tadashi Nakata

Vinyl Polymerization. CLXXII. Polymerization of Methyl Methacrylate Initiated by Nickel Peroxide

Abstract When nickel peroxide was used as an initiator of the polymerization of methyl methacrylate, it was found that the radical polymerization proceeded easier than styrene under similar conditions, and that the polymers obtained at low temperatures showed somewhat increased syndiotactic sequence as compared with ordinary radical polymers. From the NMR determinations of the polymers resulted by nickel peroxide at various temperatures, the Bovey-Tiers relationship, that is, that the probabilities of formation of isotactic, syndiotactic, and heterotactic triads of monomer unit among the polymer chain are controlled by a single parameter of the probability of isotactic addition of monomer in the propagation step was confirmed in this case. Similarly, the ratio ki/ks in rate constants for isotactic and syndiotactic additions in the polymerization by nickel peroxide in bulk was expressed by the following equation: In this equation, the difference in activation energy and entropy were somewhat larger than th...

Vinyl Polymerization. CLXXIII. Effects of Water and Some Reducing Agents on the Polymerization of Vinyl Monomers Initiated by Nickel Peroxide

Abstract The polymerization of vinyl monomers such as styrene, methyl methacrylate, acrylonitrile, vinyl acetate, and vinyl chloride was carried out in the presence of water with nickel peroxide as a solid radical initiator. It was found that the rates of polymerizations of the monomers markedly increased with the presence of water, except in the case of styrene, and the molecular weights of the polymers obtained in water were higher than those obtained in toluene. The accelerating effect of water was closely related to the solubility of the monomer used in water. The stereoregularities of the polymers resulting from methyl methacrylate, however, were observed to be rather random. The effects of some organic and inorganic reducing agents on the rate of polymerization of methyl methacrylate or styrene initiated by nickel peroxide, and on the molecular weight and the stereoregularity of the resulting polymers were also investigated.

The Thermal Dimerization and Polymerization of 1,3-Cyclohexadiene

Abstract The thermal polymerization of 1,3-cyclohexadiene to produce dimer and low molecular weight polymer is reported. The reaction initiated thermally and/or by benzoyl peroxide is kinetically of the second order, and the activation energy is 13.1 kcal/mole. The activation energy for the reaction is in quantitative agreement with that of the homopolymerization of 1,3-cyclohexadiene estimated from the kinetic study on the copolymerization with acrylonitrile. Evidently the dimerization process to give dimer as a product of typical Diels-Alder condensation is a competing type of reaction with radical polymerization to give a low molecular weight polymer. The ratio of the rate constant for two competing types of reaction at 200°C is found to be 1.21. The thermal polymerization in the presence of oxygen produces dimer in greater yield as a result of inhibition of the radical polymerization process.