Effects of solvent on model copolymerization reactions. A 13C-NMR study

Abstract

Relative reactivities of methyl methacrylate (MMA) styrene and vinyl acetate (VAc) towards the 2-methyl-2-(methoxycarbonyl)ethyl (1) and cyanoisopropyl (2) radicals have been determined in three solvents (benzene, ethyl acetate and methanol). The experiments involved 13C-NMR analysis of the 13C-labelled end-groups of copolymers formed with either azo-bis-(methylisobutyrate-α-13C) or azo-bis(isobutyronitrile-α-13C) as initiator. Relative reactivities of styrene vs MMA and MMA vs VAc were the same in benzene and ethyl acetate. Use of methanol as solvent was found to enhance slightly the relative reactivity of styrene vs MMA towards both radicals. The significance of these results is discussed ..