This article describes a rhodopsin-inspired photosensitive polymer whose light-tunable acid sensitivity can be widely modulated simply by adjusting the position of a single methoxy substituent in the aromatic rings of cinnamyl groups. The well-defined poly(5-ethyl-5-methacryloyloxymethyl-2-(p-methoxystyryl)-[1,3]dioxane) (PEMpMSD) and poly(5-ethyl-5-methacryloyloxymethyl-2-(o-methoxystyryl)-[1,3]dioxane) (PEMoMSD) as well as poly(5-ethyl-5-methacryloyloxymethyl-2-styryl-[1,3]dioxane) were synthesized via reversible addition-fragmentation chain transfer (RAFT) process. The results demonstrated that the para-methoxy substitution of EMpMSD monomer led to the more shortened initialization period and rapid chain propagation of RAFT process than 5-ethyl-5-methacryloyloxymethyl-2-styryl-[1,3]dioxane monomer under mild visible light radiation at 25 degrees C. The ortho-methoxy substitution of PEMoMSD led to high degree of photoinduced Z-isomerization over 80%. Moreover, the para-methoxy substitution of PEMpMSD led to the rapid hydrolysis of the cyclic acetal linkages in ambient acid media, while the ortho-methoxy substitution of PEMoMSD slowed down this hydrolysis. This hydrolysis slowed down on Z-isomerization particularly in PEMoMSD. These effects widely broadened the tunability of the light-modulated acid sensitivity. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011