PHOTOOXIDATION OF SILOXANE POLYMERS UNDER VACUUM ULTRAVIOLET IRRADIATION

Vacuum ultraviolet(VUV) irradiation (wavelength 147 nm) of siloxane polymers in the presence of air was studied using ATR FTIR and XPS spectroscopy. The ATR FTIR study revealed the formation of CO and OH groups in the surface layer depending on irradiation time and air pressure. The concentrations of CO and OH groups level off with the increase of irradiation time and pass through the maximum value with the increase of pressure in the range of 0.1-100torr. The XPS study of irradiated polysiloxane films demonstrated that intermolecular crosslinking via oxygen atoms also takes place on the polymer surface. The concentrations of the most important oxygen species O and O3, produced by VUV photolysis of air and coming to the polymer surface were calculated for the air pressure range 0.1-100torr. The photooxidation mechanism for siloxane polymers under VUV irradiation in air has been proposed.