Features of radical polymerization in alcohols of vinylpyridinium salts, varying the hydrophilic/phobic balance

Abstract

A kinetic study has been made of the radical polymerization of 2-methyl-5-vinylpyridine salts with ethyl and octyl bromoacetic esters in methanol, ethanol and butanol. Increases in the polymerization rate occur in this order and also in the case of the more bulky substituent. Elementary rate constants k p and k t for chain propagation and termination have been calculated. It was found that k p is constant for all the systems, which is associated with a single form of the monomers in an alcoholic medium with slightly dissociated ionogenic groups. The k t values decrease in the order methanol-ethanol-butanol on account of increasing solvent viscosities. In addition, k t decreases with increasing size of the aliphatic substituent in a monomer. The effect is explained by inhibition of rotational diffusion of the propagating radicals. A lower rate of rotation of the growing chain end in the case of the 2-methyl-5-vinylpyridine salt with octyl bromoacetic ester was detected, using a “spin trap” method.