Photo-oxidation of cured fluorinated polymers IV. Photo-oxidation of the fluorinated copolymer network with urethane linkage

The photochemical behaviour of an aliphatic polymer network based on a fluo rinated copolymer with urethane linkages was investigated. Polymer samples were submitted to irradiation at long wavelength (lambda > 300 nm) in the p resence of oxygen. The evolution of the structure was monitored by FTIR ana lysis and the different photoproducts identified. We first studied the beha viour of a model compound (HDT-BDO) which has only urethane functions as po tential sites of oxidation to determine the specific reactivity of such sit es, We determined the photo-oxidation mechanisms of the urethane site. Then , we studied the photo-oxidation of the fluorinated polymer network (PUF) w hich has several sites of oxidation (ether and urethane). We show that the ether and urethane sites had a quite similar reactivity in these cured poly mers, in contrast to classical aliphatic poly(ether-urethane) for which oxi dation results from the high sensitivity of the polyether soft segments, (C ) 2000 Elsevier Science Ltd. All rights reserved.