Initiation mechanisms in free radical polymerization: Competitive reaction of cyanoisopropyl radicals with styrene and acrylonitrile

The competitive reactions of cyanoisopropyl radicals with the mixed monomers styrene and acrylonitrile have been investigated using the nitroxide radical trapping technique. When the trap concentration is kept low, second, third, and even fourth generation tin terms of successive monomer addition) carbon radicals have been observed as trapped products. The ratio of rate constants for the addition of styrene and acrylonitrile to cyanoisopropyl radicals is 2.7 at 75 degrees C and 5.3 at 105 degrees C. These values are compared with the ratios for reactions of these two monomers with a number of other radicals and discussed in terms of the polarities of the radicals and monomers. (C) 1998 John Wiley & Sons, Inc.