High glass transition temperature bio-based copolyesters from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and isosorbide

New renewable copolymers were prepared from reactive bis-hydroxylated poly(3-hydroxybutyrate-co-3-hydroxyvalerate) oligomers (PHBHV-diol), isosorbide and 1,4-phenylene diisocyanate. First, microwave (MW)-assisted alcoholysis in the presence of ethylene glycol provides a rapid and straightforward method for engineering PHBHV-diol, with molar masses ranging from 700 to 4100 g mol−1. These well-defined oligoesters were further used for the preparation of random copolymers of PHBHV-diol and isosorbide bridged with 1,4-phenylene diisocyanate via urethanization. The molar masses (Mn) of most copolyesters are about 10,000 g mol−1 with polydispersities (DPI) in the range of 1.2-1.9. The dependence of the solid-state structures on the length of PHBHV block was carefully investigated. The incorporation of isosorbide units into the PHBHV backbone increased the glass-transition temperatures from +5 °C up to +34 °C.