PHOTOCHEMICAL BEHAVIOR OF POLY(ORGANOPHOSPHAZENE)S .12. PHOTOOXIDATION OF NA-POLY[BIS(4-BENZYLPHENOXY)-LAMBDA-5-PHOSPHAZENE] AT SHORT AND LONG WAVELENGTHS UNDER ACCELERATED CONDITIONS

In this paper the mechanism of the thermo- and photo-oxidation of na-p oly[bis(4-benzyl-phenoxy)-lambda5-phosphazene] films at short and long wavelengths has been followed under accelerated conditions using FTIR and UV-visible spectroscopic techniques. The decrease of the band at 1 453 cm-1 and the simultaneous appearance of new bands at 3 400 and 3 481 cm-1, due to free and bonded hydroperoxides, show that the primar y hydroperoxidation in this polymer occurs at -CH2- groups belonging t o benzylic moieties. According to our previous paper, the bands observ ed in the carbonyl region at 1 657, 1 704 and 1 725 cm-1 during photo- oxidation have been assigned to the formation of benzophenone, benzald ehyde and benzoic acids (dimers), respectively. The formation rate of benzophenone groups increases during irradiation at long wavelengths ( lambda > 400 nm). Under thermo-oxidative condition (90-degrees-C), ben zophenone groups are the main oxidation products derived from hydroper oxide decomposition. In addition, the photo-oxidation of a film pre-th ermo-oxidized for 500 h shows clearly that the benzophenone groups can generate aldehydes, benzoic acids and peracids. Crosslinking takes pl ace in high yields by hydrogen abstraction occurring at both benzylic and secondary alcohol units. The regeneration of benzophenone groups h as been evidenced during the photo-oxidation.