2,6-Dimethyl-5-methylene-1,3-dioxa-4-one (DMDO), a cyclic acrylate possessing acetal-ester linkage, was obtained as a mixture of cis- and trans-isomers (95:5) from Baylis-Hillman reaction of an aryl acrylate. The radical and anionic polymerizations of DMDO yielded the corresponding vinyl polymers without any side reactions such as cleavage of the acetal-ester linkage. The polymerization behaviors were significantly different from that of the acyclic acrylate, alpha-(hydroxymethyl) acrylic acid, which was expected inactive against polymerization due to the steric hindrance around the vinylidene group by the alpha-substituent. The acetal-ester linkage of the obtained polymer (P1) was completely cleaved via acid hydrolysis to afford a water soluble polymer, P2. (C) 2015 Wiley Periodicals, Inc.