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 fluorinated copolymer with urethane linkages was investigated. Polymer samples were submitted to irradiation at long wavelength (lambda > 300 nm) in the presence of oxygen. The evolution of the structure was monitored by FTIR analysis and the different photoproducts identified. We first studied the behaviour of a model compound (HDT-BDO) which has only urethane functions as potential sites of oxidation to determine the specific reactivity of such sites, We determined the photo-oxidation mechanisms of the urethane site. Then, we studied the photo-oxidation of the fluorinated polymer network (PUF) which has several sites of oxidation (ether and urethane). We show that the ether and urethane sites had a quite similar reactivity in these cured polymers, in contrast to classical aliphatic poly(ether-urethane) for which oxidation results from the high sensitivity of the polyether soft segments, (C) 2000 Elsevier Science Ltd. All rights reserved.