"The contact lens according to claim 21 wherein A is selected from the group consisting of 2-cyanoacryloxy, acrylonitryl, acrylamido, acryloxy, methacryloxy, styryl, N-vinyl-2-pyrrolidinone-3-yl, N-vinyl-2-pyrrolidinone-4-yl and N-vinyl-2-pyrrolidinone-5-yl and R is an alkylene radical and R1, R2, R3 and R4 is an alkyl radical having from 1 to 10 carbon atoms." . . . . . .