J. K. Allen, J. C. Bevington
Jul 4, 1961
Citations
0
Influential Citations
14
Citations
Journal
Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences
Abstract
Di-tert. butyl peroxide labelled with carbon-14 has been used to initiate the polymerization of styrene, and the resulting polymers have been analyzed for fragments derived from the peroxide. Polymers prepared in benzene solution contain both tert. butoxy and methyl end-groups, the proportions depending upon the conditions prevailing during polymerization; except at low concentrations of styrene and high temperatures, initiation is chiefly by the tert. butoxy radical giving polymer molecules with ether end-groups. In some diluents, initiation is largely by an indirect process in which the primary radicals abstract hydrogen from the diluent. There is an isotope effect in the dissociation of the tert. butoxy radical; introduction of carbon-14 into the radical reduces by about 7% the velocity constant for dissociation to give acetone at 130°C. Allowance must be made for this effect when using the labelled peroxide as a source of tert. butoxy radicals to be used in competitive studies of the reactivities of substances towards these radicals.