Oxydation photothermique et photocatalysée des polyundécanamides

Abstract

Abstract Photothermal and TiO 2 ‐ or ZnO‐photocatalyzed oxidations of type B‐ and type K‐polyundecanamides (RILSAN) were studied analytically and kinetically. IR spectrophotometry and chemical titration showed that hydroperoxy groups in the polymer reach a fairly high photostationary concentration. Then the primary photoproducts A decompose into products with imido groups ( C ), the concentration of which are increasing until a photostationary value. Under irradiation, the imides C are converted into acids and amides; in thermooxidation acids are the main products. The intermediate products in photocatalysed oxidation were found to be the same as in photochemical oxidation; a photochemical protection of hydroperoxides and imides was observed, due to the inner filter effect of the absorbing pigments. It could be shown that in polychromatic light the photocatalytic activity of TiO 2 (rutile) is more important than its inner filter effect; this antagonism does not depend on the concentration of the photoactive pigment.