A new method is reported for synthesizing AB-type diblock copolymer polycaprolactone-block-polystyrene (PCL-b-PSt) from a novel bifunctional initiator 2.2.2-trichloroethanol (TCE) by combining two different polymerization techniques: enzymatic ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Trichloromethyl terminated PCL was prepared by enzymatic ROP of epsilon-caprolactone (epsilon-CL) in the presence of Novozyme-435 and TCE as biocatalyst and initiator, respectively, and subsequently employed in ATRP of styrene (St) using CuCl/2, 2'-bipyridine (bpy) as the catalyst system. The GPC and NMR analysis indicated the formation of the diblock copolymer including the biodegradable PCL block and the well-defined PSt block.