Abstract
Bulk polymerization of dimethyl, diethyl, di-n-propyl, di-n-butyl and dioctyl itaconate was studied by dilatometry at 50°C, using α, α′-azobisisobutylonitrile as initiator. The rate of polymerization Rp is proportional to the square root of initiator concentration and k0, in the equation Rp=k0[M][I]1/2, increases as the alkyl group changes from methyl to octyl. This fact is explained as follows. In the polymerization of itaconates, chain transfer of allylic hydrogen often occurs, producing rather stable radicals which delay the next propagation. Therefore, the higher alkyl itaconates should have larger k0 if it can be considered that the higher becomes the alkyl group, the less becomes the chance of chain transfer because of steric hindrance of the alkyl group.
