A copolymer obtainable by polymerization of monomers, and, where is a monomer of formula where A represents C 2 - to C 4 -alkylene, B represents a C 2 - to C 4 -alkylene other than A, R represents hydrogen or methyl, m is from 1 to 500; n is from 1 to 500, and the sum total of m + n is from 2 to 1000; is an ethylenically unsaturated monomer which contains an aromatic group and is a compound of formula (IIa) or (IIb): where X a represents an aromatic or araliphatic radical having 3 to 30 carbon atoms which optionally contains one or more of the hetero atoms N, O and S, Z a represents H or (C 1 -C 4) -alkyl, Z b represents H or (C 1 -C 4)-alkyl, and Z c represents H or (C 1 -C 4)-alkyl; where R 1 represents hydrogen or methyl, X b represents an aromatic or araliphatic radical having 3 to 30 carbon atoms which optionally contains one or more of the hetero atoms N, O und S, W a represents oxygen or an NH group. is an ethylenically unsaturated monomer which contains an alkyl radical and is a compound of formula: where R 2 represents hydrogen or methyl, Y represents an aliphatic hydrocarbyl radical having 6 to 30 carbon atoms, which may be linear or branched or else cyclic, and which may contain hetero atoms O, N and/or S and may also be unsaturated, W b represents oxygen or an NH group. is a monomer of formula where A represents C 2 - to C 4 -alkylene, B represents a C 2 - to C 4 -alkylene other than A, R represents hydrogen or methyl, m is from 1 to 500; n is from 1 to 500, and the sum total of m + n is from 2 to 1000; A represents C 2 - to C 4 -alkylene, B represents a C 2 - to C 4 -alkylene other than A, R represents hydrogen or methyl, m is from 1 to 500; n is from 1 to 500, is an ethylenically unsaturated monomer which contains an aromatic group and is a compound of formula (IIa) or (IIb): where X a represents an aromatic or araliphatic radical having 3 to 30 carbon atoms which optionally contains one or more of the hetero atoms N, O and S, Z a represents H or (C 1 -C 4) -alkyl, Z b represents H or (C 1 -C 4)-alkyl, and Z c represents H or (C 1 -C 4)-alkyl; where R 1 represents hydrogen or methyl, X b represents an aromatic or araliphatic radical having 3 to 30 carbon atoms which optionally contains one or more of the hetero atoms N, O und S, W a represents oxygen or an NH group. X a represents an aromatic or araliphatic radical having 3 to 30 carbon atoms which optionally contains one or more of the hetero atoms N, O and S, Z a represents H or (C 1 -C 4) -alkyl, Z b represents H or (C 1 -C 4)-alkyl, and Z c represents H or (C 1 -C 4)-alkyl; R 1 represents hydrogen or methyl, X b represents an aromatic or araliphatic radical having 3 to 30 carbon atoms which optionally contains one or more of the hetero atoms N, O und S, W a represents oxygen or an NH group. is an ethylenically unsaturated monomer which contains an alkyl radical and is a compound of formula: where R 2 represents hydrogen or methyl, Y represents an aliphatic hydrocarbyl radical having 6 to 30 carbon atoms, which may be linear or branched or else cyclic, and which may contain hetero atoms O, N and/or S and may also be unsaturated, W b represents oxygen or an NH group. R 2 represents hydrogen or methyl, Y represents an aliphatic hydrocarbyl radical having 6 to 30 carbon atoms, which may be linear or branched or else cyclic, and which may contain hetero atoms O, N and/or S and may also be unsaturated, W b represents oxygen or an NH group.