Molecular design of block and graft copolymers by vinyl‐substituted xanthates

The selective polymerization behavior of O‐ethyl S‐4‐vinylbenzyl xanthate (1) was investigated on the basis of polymerization kinetics in the dark and in the presence of UV‐light. S‐Benzyl O‐ethyl xanthate (2) was used as a non‐polymerizable model compound of 1 to evaluate chain transfer constants. In the homopolymerization and the copolymerization of 1 initiated with AIBN in the dark, styryl groups selectively take part in the polymerization, and xanthate groups are not responsible for it. The monomer reactivity ratios (r1 = 0,51 and rMMA = 0,41) of 1 with methyl methacrylate (MMA) are very close to those of styrene with MMA. The photolysis of 2 was investigated by 1H NMR. It was found that photodecomposition of 2 takes place at CH2S (a) and SC( = S) bonds (b) with the ratio: a/b = 1/5. The polymerization of MMA was carried out with 1 upon photoirradiation. Number‐average degrees of polymerization of the polymers obtained increase linearly with conversion. Block and graft copolymers were prepared by using these macrophotoinitiators.