According to an aspect of the present invention, bioactive polymers are provided which have (a) a hydrophilic bioactive portion and (b) at least one hydrophobic polymer group that is linked to the hydrophilic bioactive portion by a covalent linkage that contains a chain transfer agent residue. According to another aspect of the present invention, medical articles are provided with bioactive surface by coating them with a coating material that contains such bioactive polymers.