An imidazole-initiated copolymerization of an aromatic bislactone, 10-methyl-2H,8H-benzo[1,2-b:5,4-b']bipyran-2,8-dione (1), and glycidyl phenyl ether (GPE) was investigated. In spite of the bifunctional nature of I that would potentially permit formation of networked and thus insoluble polymers upon its copolymerization, only one of the two lactone moieties of 1 exclusively underwent the copolymerization to give a linear polyester. Spectroscopic analysis of the polyester and its reductive scission into the corresponding fragment revealed that the polyester was formed by a 1:1 alternating copolymerization of GPE and the lactone moiety of 1. The other lactone in I that did not participate in the copolymerization was quantitatively incorporated into the side chain of the polyester as a reactive site, of which ring-opening reactions by amine and alcohol as nucleophilic reagents allowed chemoselective polymer reactions. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47:1661-1672,2009