PHOTOLYSIS AND PHOTOOXIDATION OF UNSATURATED POLYESTERS POLYMALEATE .1.

The photochemical changes involved in the photolysis and in the photo-oxidation at long wavelengths (lambda greater-than-or-equal-to 300) of poly(propyleneglycol-maleate) have been analysed by means of FTIR and u.v. spectrophotometries when the unsaturated polyester has not been crosslinked; photo-isomerization, dimerization and dissociation of fumarate groups are observed through the specific excitation of these groups in the absence of oxygen. In the presence of oxygen, photodimerization is inhibited, photo-isomerization and dissociation proceed and hydroxylated and carbonylated groups are formed. Crosslinking of poly-(propyleneglycol-maleate) through addition of increasing content of styrene (30-50%) does not prevent direct excitation of the residual fumarate groups. The three basic photoprocesses still occur. Throughout the photo-oxidation of the crosslinked UP, specific oxidation products are formed on the styrene links, such as acetophenone groups; these oxidized groups are formed together with the oxidation products of the UP-chain.