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

We report the highly isoselective ring-opening polymerization (ROP) of racemic ß-butyrolactone (ß-BL) using in situ-generated catalysts based on Y[N(SiHMe2)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 (Pm up to 0.89) in ROP of ß-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 (Tm ≈ 140 °C) and drastically reduced brittleness. The produced PHB showed an elongation at break of 392%, thus demonstrating promising polyolefin-like thermomechanical material properties.