Photolyse et photo-oxydation de polyesters insatures—2. Comportement du polymaleate-isophtalate de propylene glycol reticule ou non

Abstract

The chemical changes during the photolysis and the photooxidation at long wavelengths ( λ ⩾ 300 nm) of poly(propylene glycol-maleate-isophthalate) have been examined by FTIR and u.v. spectrophotometry. In the absence of oxygen, as a result of excitation at λ ⩾ 300 nm, photoisomerization and photodimerization of the fumarate groups were observed in non-crosslinked polyesters; photodissociation of phthalate groups also occurs. In the presence of oxygen, photodimerization is inhibited, photoisomerization and photodissociation proceed and hydroxylated and carbonylated oxidation photoproducts are formed. Crosslinking of poly(propylene glycol-maleate-isophthalate) with increasing content of styrene does not modify the excitation of fumarate and phthalate groups. Oxidation of the styrenic links is, however, observed, especially through the formation of products highly absorbing in the u.v.-visible range. Cross-linking of poly(propylene glycol-maleate-isophthalate) with mixtures of styrene and methyl methacrylate increases the photooxidability of the polyester and decreases the formation of photoproducts absorbing in the u.v.-visible.