This study reports an application of trichloroethanol (TCE) as a bifunctional initiator for the synthesis of block copolymers (BCPs) by organocatalyzed ring-opening polymerization (OROP) and atom transfer radical polymerization (ATRP). TCE was employed to synthesize a low dispersity poly (valerolactone) macroinitiator, which was subsequently used for the ATRP of tert-butyl methacrylate. While it is known that TCE can serve as an initiator in ATRP, the ability to induce polymerization under OROP is reported for the first time. The formation of well-defined BCPs was confirmed by gel permeation chromatography and H-1 NMR. Computational studies were performed to obtain a molecular-level understanding of the ring-opening polymerization mechanism involving TCE as initiator. (C) 2015 Wiley Periodicals, Inc.