Conformational Control of Radical Benzyl Bromination in Polymers from Methylstyrenes

Atactic and isotactic poly(3,4dimethylstyrenes)(poly(3,4-DMSt)h)a ve been subjected to benzylic radical bromination using either the N-bromosuccinimidebenzoyl peroxide (NBS-BPO) or the Br2-K2C03-light systems. Brominated and unbrominated polymers were studied by 13C NMR spectroscopy. A remarkable difference in the chemical reactivity of the methyl groups in positions 3 and 4 of the benzene ring between atactic poly(3,4-DMSt) and isotactic poly(3,4-DMSt) was observed. These results suggest a conformational control of the polymer main chain on the chemical reactivity of the two methyl groups on the benzene ring toward the bromine substitution reaction