A diblock copolymer consisting of tetrahydropyranyl acrylate (THPA) as a pH-deprotectable block, and a permanently hydrophobic block, methyl acrylate, was synthesized by RAFT polymerization using a quaternary amine functionalized, hydrophilic, RAFT chain transfer agent. The polymer self-assembled in water to form vesicles with D-h = 130 nm, as determined by DLS and cryogenic transmission electron microscopy. Acid catalyzed deprotection of the THPA units to yield acrylic acid resulted in a vesicle to micelle morphology transition, as evidenced by the decrease in hydrodynamic diameter to D-h = 19 nm and the observation of micelles by dry state transmission electron microscopy. (c) 2014 Wiley Periodicals, Inc.