Use of pyrazoles as ligands greatly enhances the catalytic activity of titanium iso-propoxide for the ring-opening polymerization of l-lactide: a cooperation effect

Using TiO Pr with a pyrazole ligand for one-pot LA polymerization improved catalytic activity compared with using TiO Pr only. At 60 °C, TiO Pr with Pz exhibited a higher catalytic activity (approximately 3-fold) than TiO Pr . At room temperature, TiO Pr with Pz exhibited a higher catalytic activity (approximately 17-fold) than TiO Pr . High molecular mass PLA ( = 51 100, and = 1.10) could be produced by using TiO Pr with Pz in melt polymerization ([TiO Pr ] : [ Pz] = 1000 : 1 : 1 at 100 °C, 240 min). The crystal structure of Pz Ti O Pr revealed the cooperative activation between two Ti atoms during LA polymerization.