Crosslinked poly(mereapto-thiourethane) was employed as a precursor for graft copolymer synthesis. The crosslinked stem polymer (1) was easily prepared by polyaddition of a bifunctional dithiocarbonate and piperazine under air atmosphere via oxidative coupling of mercapto, group. Polymerization of styrene and methyl methacrylate in the presence of 1 yielded the corresponding crosslinked graft copolymers with high grafting weight percentages (>1800%). (c) 2005 Wiley Periodicals, Inc.