THE AUTOXIDATION OF POLY(PROPYLENE OXIDE)S

The autoxidation of poly(propylene oxide)s of molecular weights 398, 1020 and 2030 at 95, 110, 125 and 140-degrees follows the same kinetic path independent of the molecular weight of the polymer indicating random hydroperoxidation along the polymer chain. When the -OH end-groups are replaced by -O-CO-NH-C2H5 groups the kinetic path is unchanged confirming random hydroperoxidation and showing similarity of polymer breakdown in simple polyether and in the derived urethane elastomers. The volatile oxidation products produced account for only approximately 2 % of the absorbed oxygen, the major part of the rest leads to water (45%) and to carbonyl groups in the structures at the ends of newly formed chains produced by scission of the polymer molecules. Vapour phase osmometry indicates at least 0.48 chain scissions for each oxygen molecule absorbed. A reaction scheme based on three routes for hydroperoxide decay is presented to rationalize the findings.