Initiation Mechanisms in Copolymerisation: Reaction of t-Butoxyl Radicals with Co-monomers Ethyl Vinyl Ether and Methyl Methacrylate

Abstract

The radical trapping technique employing 1,1,3,3‐tetramethyl‐1,3‐dihydro‐1H‐isoindol‐2‐yloxyl as a scavenger has been used to investigate the reaction of t‐butoxyl radicals with mixtures of ethyl vinyl ether and methyl methacrylate. The range of identified products includes those from both addition and hydrogen abstraction with both monomers, head addition with ethyl vinyl ether, and some second monomer addition products. Relative rate constants have been obtained for various pairs of constituent reactions. t‐Butoxyl radicals add to ethyl vinyl ether one to two times faster than to methyl methacrylate, depending on which monomer is in excess. The ratio is less than 1 in nonolefinic solvents and as high as 6 in t‐butanol. This solvent effect is thought to be due to the radicals complexing to either methyl methacrylate or t‐butanol (H‐bonding), thereby increasing its electrophilic character.