COMPARTMENTALIZED POLYMERIZATION WITH OIL-SOLUBLE INITIATORS - KINETIC EFFECT OF SINGLE RADICAL FORMATION

The stationary state distribution of radicals in compartmentalized sys tems initiated by oil-soluble initiators have been calculated for vari ous cases of single radical formation as well as a simultaneous genera tion of single radicals and pairs of radicals in the particles. The ef fect of a contribution from radicals produced by initiator dissolved i n the aqueous phase has been considered. Desorption and reabsorption o f radicals, aqueous phase termination, total rate of radical formation and the water-solubility of the initiator are quantified in terms of dimensionless parameters. The calculations predict that single radical s generated in the particles are kinetically indistinguishable from ra dicals produced in the aqueous phase over a wide range of variation of the parameters. It is shown that if the rate of generation of single radicals constitutes only about 10 per cent of the overall rate of rad ical formation in the particles, the former radicals account for the m ajor part of the rate of polymerization. The mechanisms previously pro posed to account for the similar kinetic behaviour observed with water -soluble and oil-soluble initiators are discussed. It is concluded tha t the present calculations support the view that this similarity is ma inly due to radicals produced by the water-soluble fraction of the ini tiator. (C) 1997 John Wiley & Sons, Inc.