Synthesis and Characterization of Novel Copoly(ester−urethane) Containing Blocks of Poly-[(R)-3-hydroxyoctanoate] and Poly-[(R)-3-hydroxybutyrate]

Novel poly(ester−urethane) block copolymer has been synthesized by use of telechelic hydroxylated poly-[( R )-3-hydroxyoctanoate] (PHO-diol) with number-average molecular weight ( M n ) of 2400 as the amorphous soft segment, telechelic hydroxylated poly-[( R )-3-hydroxybutyrate] (PHB-diol) with M n of 2600 as the crystalline hard segment, and l -lysine methyl ester diisocyanate (LDI) as the junction unit. Reaction of the PHO-diol, PHB-diol, and LDI at a ratio of 1:1:2 in the presence of dibuthyltin dilaurate as catalyst afforded the block copolymer in 70% yield with a molecular weight ( M w ) of 33 500 (GPC) and a M n of 10 600 (VPO). The chemical structure of the new polymer was confirmed by 1 H NMR, 13 C NMR, and IR spectra. On average, 2 PHO-diol, 2 PHB-diol, and 5 LDI were incorporated in each molecule of the block-copoly(ester−urethane). The thermoplastic properties were very good with a melting temperature ( T m ) of 146 °C and the glass transition temperature ( T g ) of −6 °C (DSC). The mechanical properties, obtained from the stress/strain test, are comparable with other biocopolyester and block-copoly(ester−urethane).