Hydrogen atom abstraction from polystyrene by t-butoxyl radicals, studied by spin trapping; effect of conformation on reactivity

Abstract

A spin trapping technique was employed to examine the reactivity of polystyrene towards t-butoxyl radicals in solution at room temperature, with 2-methyl-2-nitrosopropane (MNP) and di-t-butyl peroxyoxalate (DBPO) as spin trapping reagent and t-butoxyl radical source, respectively. The polymer-derived radical produced by hydrogen atom abstraction was trapped by MNP; it was found that the polystyrene was selectively attacked at the tertiary positions. A comparison of the reactivities of polystyrene and anisole towards t-butoxyl radicals was made by direct integration of e.s.r. spectra of two spin adducts of radicals produced by hydrogen atom abstraction. The relative reactivity of polystyrene was found to increase with decreasing molecular weight and with dilution of the solution with benzene. These results suggest that the reactivity of polystyrene depends mainly on the nature of its coiled conformation in solution.