The present invention provides a copolymer obtainable by polymerizing a monomer mixture which contains at least compounds of the following formulae (A), (B) and (C), wherein Ta, Tb, Tc, Ua1, Ua2, Ub1, Ub2 and Ub3, Qa, Qb and Qc, Ra, Rb and Rc, An− and m are as defined in Specification and Claims, and so on. The copolymer of the present invention can be utilized as an ion complex material excellent in a function of inhibiting adhesion of a biological substance.
