Hydrophilic group-containing ab-type block copolymer

Abstract

An AB-type block copolymer represented by formula (I): ##STR1## wherein R.sup.1 represents a hydrocarbon group having 1 to 10 carbon atoms; R.sup.2 represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms; R.sup.3 represents a benzyl group, ##STR2## wherein R.sup.4 represents an alkyl group having 1 to 10 carbon atoms, or an alkyl group having 1 to 18 carbon atoms; M represents a group represented by the formula (M.sup.2).sub.m --(M.sup.1).sub.n or (M.sup.1).sub.m --(M.sup.2).sub.n, each of m and n being a natural number of 20 to 5000; is prepared by a process of first polymerizing either a monomer for forming the M.sup.1 block or a monomer for forming the M.sup.2 block in the presence of a sulfur-containing compound having formula (XIII): ##STR3## wherein R.sup.1, R.sup.2 and R.sup.3 are as defined above so as to synthesize a polymer initiator having a dithiocarbamate group as indicated in formula (XIII) at the polymer terminal end, and then polymerizing the other monomer in the presence of the polymer initiator obtained in the first step; wherein the polymerization reactions in the first step and in the second step are carried out upon exposure of the monomers to ultraviolet radiation.