Photodegradation of polyethersulfone and polysulfone

Abstract

The photolysis and the photooxidation of polyethersulfone (PESF) and bisphenol-A polysulfone (PSF) have been investigated under polychromatic (λ>300 nm) and monochromatic irradiations (254 and 365 nm). Under vacuum exposure, as a result of direct absorption of the incident radiation by the basic backbone structure of polyarylsulfones (PESF and PSF), the photolytic processes that occur involve chain scissions as revealed by UV–visible and high performance liquid chromatography (HPLC) identifications of the fluorescent low molecular weight fragments after methanolic extraction. In parallel, Fourier transform infrared (FTIR) spectroscopy of the irradiated films accounts for the photoreduction of sulfone moieties in benzenesulfinic acid end-groups and for the formation of phenolic extremities after photo-Claisen-type rearrangement of the ether moieties or direct chain scission and subsequent hydrogen abstraction. Phenyl radicals recombination accounts for the pronounced yellowing of the polymer. Under exposure in aerated media, the rapid photooxidation of both polymers involves chain scissions and the formation of numerous carbonylated and hydroxylated oxidative species. The experimental results indicate that most of the oxidation products arise from the photodegradation of the diphenylethersulfone moieties and the cleavage of the aromatic rings; the oxidation of the bisphenol-A moieties occurs only in secondary steps. As a consequence of the chain scissions provoked by the oxidation, the photoproducts are predominantly low molecular weight oxidation products and most of the consumed oxygen appears readily as carbon dioxide.