Polystyrene, PSt, (Mn≈ 14 000) containing CCl3end groups was obtained by free radical polymerization of styrene, St, initiated by decomposition of azo roups of 4, 4′-azo-bis-(4-cyanopentane-trichloroacetylamide), ACPT, in dimethylformamide solution at 70°C. This polymer was used as initiator for free radical polymerization of methylmethacrylate, MMA. Free radical sites located at the end of PSt chains were generated photochemically (λinc= 436 nm) with the aid of Mn2(CO)10. St/MMA block copolymer containin 72 to 86 mol% MMA was obtained from the crude product after extraction of unreacted PSt with boilin cyclohexane. The results demonstrate that ACPT can be applied as a bifunctional initiator for the synthesis of block copolymers of type AnBmor AnBmAn, consisting of monomers A and B prone to free radical polymerization.