End Groups of Poly(Methyl Methacrylate-Co-Styrene) Prepared with Tert-Butoxy, Methyl, and/or Phenyl Radical Initiation: Effects of Solvent, Monomer Composition, and Conversion

Abstract

The relative reactivities of iert-butoxy, methyl, and phenyl radicals toward styrene, methyl methacrylate, and several solvents (acetone, butan-2-one, toluene, and benzene) have been established by means of competition experiments. These experiments demonstrate that when a source of tert-butoxy radicals is employed as the initiator for copolymerization and toluene or butan-2-one is used as the solvent, a majority of end groups may be solvent derived. This is a consequence of the iert-butoxy radicals' high propensity for hydrogen abstraction. Even with benzene as solvent, there is a significant proportion of solvent attack and resultant phenyl radical initiation. A second major influence of t..