Synthesis and characterization of waterborne polyurethane containing poly(3-hydroxybutyrate) as new biodegradable elastomers

Poly(3-hydroxybutyrate) (PHB) is a biodegradable polymer with good biocompatibility. The crystalline and brittle nature has limited its processing for further applications. In this study, PHB diols were employed as a part of the soft segment to synthesize waterborne polyurethane (PU). Poly(e-caprolactone) (PCL) diol was used as the major soft segment (80 mol%) and blended with PHB diol (20 mol%) at the beginning of the synthesis. PHB diols with three different molecular weights (1352, 1679, and 2062 g mol(-1)) were respectively used. The microphase separation was adjusted by changing the prepolymerization temperature. Physico-chemical characterization revealed that the PCL-PHB-based PUs had 3-7% crystallinity, good flexibility (similar to 1-8 MPa modulus and similar to 500% elongation), and some shape memory behavior (up to similar to 80% shape recovery). The use of higher molecular weight PHB diol (2062 g mol(-1)) and a prepolymerization temperature at 95 degrees C gave rise to PU with the best properties in general. The latter PU also showed excellent biodegradation (52% weight loss after 30 days) and biocompatibility (capsule thickness similar to 23 mu m) in vivo. Furthermore, the PU dispersion could be electrospun into nanofibers (similar to 400 nm diameter) without the use of organic solvents. Therefore, the eco-friendly PU containing PHB blocks has good mechanical properties, processing abilities, and biocompatibility, and may be a new category of biodegradable elastomers and potential biomaterials for cardiovascular and other medical applications.