Semi-interpenetrating networks of bacterial poly(3-hydroxybutyrate) with net-poly(ethylene glycol)

Semi-interpenetrating network (IPN) hydrogels based on bacterial poly(3-hyd roxybutyrate) (PHB) and net-poly(ethylene glycol) (net-PEG) were prepared b y the UV irradiation technique. The swelling and thermal behavior of the hy drogels, os well as their mechanical properties were studied by means of sw elling tests, differential scanning calorimetry and tensile experiments. Ne t-PEG-based hydrogels all show higher equilibrium water contents (EWCs), wh ile a remarkably decreased EWC is observed for the hydrogel containing 75% PHB. The thermal behavior of PHB in the semi-IPNs is not greatly affected b y hydrogel composition. However, the crystallinity of PEG segments is notic eably decreased by crosslinking and would further drop with increasing amou nt of PHB. Incorporation of semi-IPN structure with PHB could significantly improve the mechanical properties of hydrogels when compared with that of pure net-PEG. The PHB/net-PEG 150/50) semi-IPN2. ranking as that possessing the best mechanical properties in the wet state, is expected to be useful as a biomedical material. (C) 2001 Elsevier Science Ltd. All rights reserve d.