Development of amino-oxazoline and amino-thiazoline organic catalysts for the ring-opening polymerisation of lactide.

The ring-opening polymerisation of lactide by a range of amino-oxazoline and amino-thiazoline catalysts is reported. The more electron-rich derivatives are demonstrated to be the most highly active and polymerisation is well controlled, as evidenced by the linear relationship between the molecular weight and both the monomer conversion and the monomer-to-initiator ratio. Mechanistic studies reveal significant interactions between the monomer, initiator and catalyst and that the polymerisation is first order with respect to each of these components. These observations indicate that the polymerisation operates by a general base/pseudo-anionic mechanism.