A novel polymer bearing acyclic vicinal tricarbonyl moieties in the side chains was synthesized by (1) radical polymerization of a styrene derivative with a 1,3-diketone structure and (2) successive treatment of the resulting polystyrene derivative by N-bromosuccinimide to convert its 1,3-diketone moiety in the side chains into the corresponding vicinal tricarbonyl moiety. The tricarbonyl moiety was highly reactive with water to permit its rapid conversion into a geminal diol structure in water-containing acetone. On the other hand, heating the resulting polymer bearing the geminal diol structure under vacuum enabled successful recovery of the vicinal tricarbonyl moiety to demonstrate the reversible nature of this system, which allowed us to repeat the hydration-dehydration cycle without deteriorating the polymer structure. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 2245-2251, 2011