We successfully synthesized poly(l-lactide)-b-poly (methyl methacrylate) diblock copolymers at ambient temperature by combining ultraviolet light-induced copper-catalyzed ATRP and organo-catalyzed ring-opening polymerization (ROP) in one-pot. The polymerization processes were carried out by three routes: one-pot simultaneous ATRP and ROP, one-pot sequential ATRP followed by ROP, and one-pot sequential ROP followed by ATRP. The structure of the block copolymers is confirmed by nuclear magnetic resonance and gel permeation chromatography, which suggests that the polymerization method is facile and attractive for preparing block copolymers. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 699-704