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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) (PEM pMSD) and poly(5-ethyl-5-methacryloyloxymethyl-2-( o-methoxystyryl)-[1,3]dioxane) (PEM oMSD) 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 EM pMSD 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 °C. The ortho-methoxy substitution of PEM oMSD led to high degree of photoinduced Z-isomerization over 80%. Moreover, the para-methoxy substitution of PEM pMSD led to the rapid hydrolysis of the cyclic acetal linkages in ambient acid media, while the ortho-methoxy substitution of PEM oMSD slowed down this hydrolysis. This hydrolysis slowed down on Z-isomerization particularly in PEM oMSD. These effects widely broadened the tunability of the light-modulated acid sensitivity. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]