Synthesis and characterization of multi-block copolymers containing poly[(3-hydroxybutyrate)-co-(3-hydroxyvalerate)] and poly(ethylene glycol)

Various problems, including high crystallinity, high melting temperature, poor thermal stability, hydrophobicity and brittleness, have impeded many practical applications of poly[(3-hydroxybutyrate)-co-(3-hydroxyvalerate)] (PHBV) as an environmentally friendly material and biomedical material. In the work reported here, multi-blockcopolymers containing PHBV and poly(ethylene glycol) (PHBV-b-PEG) were synthesized with telechelic hydroxylated PHBV as a hard and hydrophobic segment, PEG as a soft and hydrophilic segment and 1,6-hexamethylene diisocyanate as a coupling reagent to solve the problems mentioned above. PHBV and PEG blocks in PHBV-b-PEG formed separate crystalline phases with lower crystallinity levels and lower melting temperatures than those of phases formed in the precursors. The crystallite dimensions of the two blocks in PHBV-b-PEG were smaller than those of the corresponding precursors. Compared to values for the original PHBV, the maximum decomposition temperature of the PHBV block in PHBV-b-PEG was 16.0 degrees C higher and the water contact angle was 9 degrees lower. In addition, the elongation at break was 2.8% for a pure PHBV fiber but 20.9% for a PHBV/PHBV-b-PEG fiber with a PHBV-b-PEG content of 30%. PHBV-b-PEGs can overcome some of the disadvantages of pure PHBV; it is possible that PHBV might be a good candidate for the formulation of environmentally friendly materials and biomedical materials. (C) 2010 Society of Chemical Industry