A comparative investigation of the radiolytic behaviour of perfluoropolyethers and their analogous non-fluorinated compounds

Abstract

A comparative investigation of the basic features of the radiolytic behaviour of perfluorinated and non-fluorinated polyethers has been undertaken by performing ESR measurements on the intermediate radical products, NMR detection of the major structural changes and GC analysis of gaseous products [A. Faucitano, A. Buttafava, A.P. Guarda, G. Marchionni, J. Fluorine Chem. (submitted); A. Faucitano, A. Buttafava, F. Martinotti, G. Marchionni, R.J. De Pasquale, Radiat. Phys. Chem., 37 (1991) 43]. The compounds investigated were perfluoro(polytrimethylene oxide), perfluoro(polypropene oxide), poly(methylene oxide), poly(ethylene oxide), poly(propene oxide) and poly- (tetramethylene oxide): CF 3CF 2CF 2O(CF 2CF 2CF 2O) n CF 2CF 3; CF 3CF 2 CF 2O[CF 2CF(CF 3)O] n CF 2CF 3; (CH 2O) n ; (CH 2CH 2O) n ; [CH 2CH(CH 3)O] n ; (CH 2CH 2CH 2CH 2O) n . The behaviour of the perfluoroethers is dominated by CC and CO bond cleavages leading to a decrease of the average molecular weight; of minor importance is the cleavage of CF bonds. In the non-fluorinated polyethers CC and CO bond cleavages take place together with the rupture of CH bonds, which is of prominent importance. This route proceeds with H abstraction by the primary ether cation-radicals and by the secondary alkyl and alkoxy radicals. The results have been rationalized with mechanisms which involve important aspects of the ion and free radical chemistry of the compounds investigated.