onadjacent carbon atoms is optionally replaced by O, S, ???CO???O???, O???CO???O, where one or more H atoms is optionally replaced by fluorine, or is an aryl group which has from 5 to 40 carbon atoms and in which one or more carbon atoms is optionally replaced by O, S or N, which is optionally substituted by one or more nonaromatic radicals R1; m is identical or different on each occurrence and is