A macroiniferter having photolabile thiuram disulfide groups an poly(ethylene glycol) segments was prepared by the solution polycondensation of bis(2-hydroxyethyl) thiuram disulfide with adipoyl chloride and poly(ethylene glycol) in the presence of triethyl amine. The macroiniferter obtained was used in the photoinduced polymerization of methyl methacrylate to yield active poly(methyl methacrylate-b-ethylene glycol) block copolymers. The active block copolymers were also used for photopolymerization of styrene to obtain multiblock copolymers. Block copolymers were characterized by spectroscopic examination, fractional precipitation and gel permeation chromatography. (C) 1998 Elsevier Science Ltd. All rights reserved.