There are disclosed according to the invention copolymers having repeating structural units a) of the formula ##STR1## and b) of the formula (II) ##STR2## wherein m and p are each independently of the other whole numbers>0, n=1, o=1 or 0, Y is a bond or a group of the formula --CR.sub.2 -- or --CO--O--CR.sub.2 --CR.sub.2 --CR.sub.2 --, each of the radicals R independently of the others is a H atom, an alkyl group, a group of the formula --CR'.sub.2 --OR', --OR', --COOR', --SiR.sub.c R.sub.d R.sub.e, or --NR.sub.d --R.sub.c, an organic acid radical, its anhydride or its corresponding readily hydrolysable ester of the formula --O--CO--R.sub.c or its corresponding readily hydrolysable amide of the formula --NR.sub.d --CO--R.sub.c, a phenyl group optionally substituted by one or two --CR'.dbd.CR'.sub.2 groups, or a group of the formula --CR.sub.e R.sub.f CHR.sub.g --SiX.sub.3, a group of the formula --SiOSiO(SiO).sub.m H, an epoxy group, an aziridine group, a phosphate or phosphorate group or an anhydride thereof or a bond, or two radicals R together represent a group of the formula .dbd.CR2, and each of the radicals R', R.sub.c, R.sub.d, R.sub.e, R.sub.f, R.sub.g and X independently of the others may be a H atom, a OH group, an alkyl group, an alkoxy group or an aryl group, with the proviso that in at least one unit of the formula II at least one radical R bonded to a Si atom is a --OH, --OR.sub.c or --NR.sub.d R.sub.c group or a radical of the formula --OCOR.sub.c or --NR.sub.d COR.sub.c.