Novel poly(3-hydroxybutyrate) and poly(ethylene glycol) (PHB/PEG) multiblock copolymers were synthesized through one-step copolymerization with hexamethylene diisocyanate (HDI) as a coupling agent by varying the block composition. Molecular structures and chemical compositions were confirmed by NMR and FTIR spectral analysis. Thermal properties and mechanical properties were investigated using differential scanning calorimetry (DSC) and stress-strain experiments, respectively. The hydrophilicity and degradability were also assessed in different media at 37 degrees C. The results show that this kind of copolymers exhibit good toughness and moderate strength in comparison with homopolymer PHB, the degradation rate and equilibrium water content (EWC) are much higher than those of the PHB homopolymer. (c) 2005 Elsevier Ltd. All rights reserved.