Aspects of some initiation and propagation processes

TLDR: In this article, it was shown that the rate of free radical polymerization can be determined as a function of the electron-accepting properties of the chelate derivatives of the metal acetylacetonates.

Abstract: SELECTIVE FREE-RADICAL INITIATION Selective initiation of free-radical polymerization is, as far as I am aware, a novel phenomenon Conventional initiators such as benzoyl peroxide and azo-bis-isobutyronitrile, which produce active radicals, are not significantly discriminating in their behaviour towards different monomers, provided these can be polymerized by a radical mechanism; indeed the rate of initiation by azo-bis-isobutyronitrile at a given concentration is essentially the same for a number of common monomers12 Recent work3 has revealed the existence of a type of initiator which is strongly selective, the rate of initiation apparently depending on the electron-accepting properties of the monomer Our interest in selective initiation of free-radical polymerization arose during studies of initiation by chelate derivatives of metals, which will now be described briefly Three groups of workers have shown that certain metal acetylacetonates can act as sources of initiating radicals4-6 Both Kastning et al5 and ourselves6 have pointed out the relatively high activity possessed by manganic acetylacetonate Mn"(acac)a compared to the simple chelates of other metals At 80°C the rate of polymerization w of bulk methyl methacrylate is given as a function of chelate concentration by the equation