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 ⁱ Pr ₄ with a pyrazole ligand for one-pot LA polymerization improved catalytic activity compared with using TiO ⁱ Pr ₄ only. At 60 °C, TiO ⁱ Pr ₄ with ^fur Pz exhibited a higher catalytic activity (approximately 3-fold) than TiO ⁱ Pr ₄ . At room temperature, TiO ⁱ Pr ₄ with ^Bu Pz exhibited a higher catalytic activity (approximately 17-fold) than TiO ⁱ Pr ₄ . High molecular mass PLA ( M _{n GPC} = 51 100, and Đ = 1.10) could be produced by using TiO ⁱ Pr ₄ with ^fur Pz in melt polymerization ([TiO ⁱ Pr ₄ ] : [ ^fur Pz] = 1000 : 1 : 1 at 100 °C, 240 min). The crystal structure of ^Me Pz ₂ Ti ₂ O ⁱ Pr ₇ revealed the cooperative activation between two Ti atoms during LA polymerization.
Competing Interests: There are no conflicts to declare.
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