Functional syndiotactic poly(β‐hydroxyalkanoate)s via stereoselective ring‐opening copolymerization of <i>rac</i>‐β‐butyrolactone and <i>rac</i>‐allyl‐β‐butyrolactone

Abstract

Abstract The copolymerization of racemic β‐butyrolactone ( rac ‐BL Me ) with racemic “allyl‐β‐butyrolactone” ( rac ‐BL allyl ) in toluene, catalyzed by the discrete amino‐alkoxy‐bis(phenolate) yttrium‐amido complex 1 , gave new poly(β‐hydroxyalkanoate)s with unsaturated side chains. The poly(BL Me ‐ co ‐BL allyl ) copolymers produced have a highly syndiotactic backbone structure ( P r = 0.80–0.84) with a random enchainment of monomer units, as evidenced by 13 C 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 ‐BL allyl ) was a linear function of the feed ratio. The pendant vinyl bond of the side‐chains in those poly(BL Me ‐ co ‐BL allyl ) 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 , Δ H m , T g ) of the prepared polymers have been also evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3177–3189, 2009