A SPIN-TRAP STUDY OF THE BENZOYL PEROXIDE INITIATED RADICAL COPOLYMERIZATION OF STYRENE AND VINYL-ACETATE

Electron spin resonance spectroscopy has been used, in conjunction with the spin-trapping technique (employing 2-methyl-2-nitrosopropane), to identify (and distinguish between) polystyrene and poly(vinyl acetate) propagating radicals. The technique has also been used to establish the relative concentrations of propagating radicals with a styrene or a vinyl acetate ultimate monomer unit at the radical end of the propagating chain in a range of styrene/vinyl acetate copolymerizations. From the data the monomer reactivity ratios have been estimated to be r(s) = 57 +/- 7 and r(VA) = 0.002 +/- 0.004.