The invention relates to copolymers of formula (I) wherein R.sup.1 is hydrogen, a C.sub.1-C.sub.5-alkyl radical or C.sub.2-C.sub.5-alkenyl radical which can also contain heteroatoms, an acid group or an aliphatic or aromatic group comprising 1-50 carbon atoms, including an acid group, R.sup.2 and R.sup.3 independently represent hydrogen, methyl and/or ethyl, n ranges from 0-100, and m ranges from 3 to 30, and k ranges from 1-200, and A is hydrogen, an acid group, a C.sub.1-C.sub.5-alkyl radical or a C.sub.2-C.sub.8-alkenyl radical which can also contain heteroatoms, an aliphatic or aromatic group comprising 1-50 carbon atoms, including an acid group, or a copolymer unit of formula (II), wherein R.sup.4 is hydrogen, a C.sub.1-C.sub.5-alkyl radical or a C.sub.2-C.sub.5-alkenyl radical which can also contain heteroatoms, an acid group or an aliphatic or aromatic group comprising 1-50 carbon atoms, including an acid group, R.sup.5 is hydrogen, methyl and/or ethyl, x ranges from 0 to 100, and y ranges from 3-30, wherein, if A is formula (2), R.sup.1 represents hydrogen or an acid group. ##STR00001##