Patent ID: 7811556

Claim:
A copolymer or a pharmacologically acceptable salt thereof, with an average degree of polymerization in the range of from 5 to 200, consisting of, as constitutional units, (a) one or more structural units which may be the same or different from each other and which are represented by the formula (I) below: wherein: m is an integer of from 3 to 100, Alk represents an alkylene group having from 1 to 6 carbon atoms, and R 1 and R 2 are the same or different and each represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms that may optionally be substituted with at least one substituent selected from the group consisting of hydroxy groups, halogen atoms and aryl groups having from 6 to 14 carbon atoms that may optionally be substituted with from 1 to 5 substituents selected from Substituents A defined below, and (b) one or more structural units which may be the same or different from each other and which are represented by the formula (II): wherein: R 3 is selected from the group consisting of an alkoxy group having from 1 to 6 carbon atoms that may optionally be substituted with at least one substituent selected from the group consisting of hydroxy groups, halogen atoms and aryl groups having from 6 to 14 carbon atoms that may optionally be substituted with from 1 to 5 substituents selected from Substituents A defined below, an aryloxy group having from 6 to 14 carbon atoms that may optionally be substituted with from 1 to 5 substituents selected from Substituents A defined below, and a group represented by the formula —NR 4 R 5 , wherein R 4 and R 5 are the same or different from each other and each represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms that may optionally be substituted with at least one substituent selected from the group consisting of hydroxy groups, halogen atoms and aryl groups having from 6 to 14 carbon atoms that may optionally be substituted with from 1 to 5 substituents selected from Substituents A defined below, and a hydroxyl group present in a ratio of 5:5 to 0:10, wherein the ratio represents said hydroxyl group:one of said other groups listed above as a selection for R 3 in the structural unit represented by formula (II) in said copolymer molecule, and Substituents A are selected from alkyl groups having from 1 to 6 carbon atoms, alkoxy groups having from 1 to 6 carbon atoms, halogen atoms, hydroxy groups, nitro groups and carboxy group.