This article describes the photosensitive polymer micelles whose structural stability and acid sensitivity can be widely tuned simply via one-batch UV irradiation. To this end, the well-defined poly(5-ethyl-5-methacryloyloxy-methyl-2-styryl-[1,3]dioxane)-block-poly[poly(ethylene glycol) methacrylate] (PEMSD-b-PPEGMA) copolymers were synthesized via RAFT polymerization under mild visible light radiation at 30 degrees C. The results demonstrated that the irradiation of the homogeneous acetone solution with UV light only induced Z-isomerization of their cinnamyl groups, while irradiating PEMSD chains in the bulky micellar cores only induced dimerization. Moreover, the micelles of previously Z-isomerized copolymer could be effectively stabilized without changing their acid sensitivity on irradiating for shortly 3 min, while UV irradiation for 30 min could remarkably improve the acid stability of these micelles. These novel properties are of potential applications in controlled drug delivery. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012