Initiation Mechanisms for Radical Polymerization of Methyl Methacrylate with tert-Butyl Peroxypivalate

The reaction of tert -butyl peroxypivalate ( 2 ) with methyl methacrylate ( 3 ) has been studied by the radical trapping technique employing 1,1,3,3-tetramethyl-2,3-dihydro-1 H -isoindol-2-yloxyl ( 1 ) as a scavenger. Thermolysis of 2 generated tert -butoxyl, tert -butyl, and methyl radicals in the ratios of 48:50:2 at 60 °C in 3 . Both alkyl radicals underwent selective tail addition to 3 . tert -Butyl radicals reacted about twice as fast as methyl radicals with 3 . The absolute rate constant for addition of tert -butyl radicals to 3 was estimated to be 2.3 × 10 6 M -1 s -1 at 60 °C. The overall ratio of addition to H abstraction in the reaction of 2 with 3 was 5:1.