The copolymerization of racemic beta-butyrolactone (rac-BLMe) with racemic "allyl-beta-butyrolactone" (rac-BLallyl) in toluene, catalyzed by the discrete amino-alkoxy-bis(phenolate) yttrium-amido complex 1, gave new poly(beta-hydroxyalkanoate)s with unsaturated side chains. The poly(BLMe-co-BLallyl) copolymers produced have a highly syndiotactic backbone structure (P-r = 0.80-0.84) with a random enchainment of monomer units, as evidenced by C-13 NMR, and high molecular weight (M-n up to 58,000 g mol(-1)) with a narrow polydispersity (M-w/M-n = 1.07-1.37), as determined by GPC. The comonomer incorporation (5-50 mol % rac-BLallyl) was a linear function of the feed ratio. The pendant vinyl bond of the side-chains in those poly(BLMe-co-BLallyl) copolymers allowed the effective introduction of hydroxy or epoxy groups via dihydroxylation, hydroboration-oxidation or epoxidation reactions. NMR studies indicated that all of these transformations proceed in an essentially quantitative conversion and do not affect the macromolecular architecture. Some thermal properties (T-m, Delta H-m, T-g) of the prepared polymers have been also evaluated. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3177-3189, 2009