AN ELECTRON-SPIN-RESONANCE STUDY OF THE RADIATION-CHEMISTRY OF POLY(HYDROXYBUTYRATE)

The spectra of the radical species resulting from gamma irradiation of poly(hydroxybutyrate) and its copolymers with hydroxyvalerate have be en obtained after radiolysis at 77 and 303 K, and the corresponding ra diation chemical yields have been calculated. Photobleaching and annea ling experiments have allowed the major radical species to be identifi ed and their reactivities to be assessed. Radical anions, as well as n eutral radicals, were observed to be present at 77 K, but the radical anions were found to decay to neutral radicals at temperatures around 140K. Above about 250 K a multi-line component of the spectrum was los t, but the radical associated with this spectral change has not been u nequivocally assigned, though it is believed to be a radical resulting from chain scission. Annealing over the temperature range 300-350 K r esulted in the loss of a triplet, which accounts for most of the radic als present. This triplet has been assigned to a radical located on th e carbon atom adjacent to the carbonyl group. This radical is believed to exist in two possible conformations. Ali of the radicals decayed a t temperatures above 400 K.