Highly Isoselective Ring-Opening Polymerization of rac-β-Butyrolactone: Access to Synthetic Poly(3-hydroxybutyrate) with Polyolefin-like Material Properties

We report the highly isoselective ring-opening polymerization (ROP) of racemic β-butyrolactone (β-BL) using in situ -generated catalysts based on YN(SiHMe 2 ) 2 3 (THF) 2 and salan-type pro-ligands. The catalyst system produces isotactic poly(3-hydroxybutyrate) (PHB) with record productivity (TOF up to 32 000 h –1 ) and the highest isoselectivity ( P m up to 0.89) in ROP of β-BL achieved to date. In contrast to bacterial PHB, the chemically synthesized PHB has beneficial material properties, such as increased melt processing window attributed to a lowered melting temperature ( T m ≈ 140 °C) and drastically reduced brittleness. The produced PHB showed an elongation at break of 392%, thus demonstrating promising polyolefin-like thermomechanical material properties.