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 fum arate groups are observed through the specific excitation of these gro ups in the absence of oxygen. In the presence of oxygen, photodimeriza tion is inhibited, photo-isomerization and dissociation proceed and hy droxylated and carbonylated groups are formed. Crosslinking of poly-(p ropyleneglycol-maleate) through addition of increasing content of styr ene (30-50%) does not prevent direct excitation of the residual fumara te 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 oxidi zed groups are formed together with the oxidation products of the UP-c hain.