| abstract |
Use of amorphous perfluorinated polymers for preparing transparent films at 157 nm, said perfluorinated polymers being free from unstable ionic end groups COF, COOH or their amidic derivatives, esters or salts, said polymers formed by cyclic units deriving from perfluorodioxoles of formula: n n n wherein R′ F is equal to R F or OR F wherein R F is a perfluoroalkyl radical having 1-5 carbon atoms; X 1 and X 2 , equal to or different from each other, are F, CF 3 ; n said polymers optionally containing units deriving from perfluorinated comonomers optionally containing oxygen atoms; n in said polymers the cyclic units deriving from the perfluorodioxoles of formula (IA) being ≧95% by moles. |