Rare earth metal-mediated ring-opening polymerisation of cyclic phosphoesters

In this report, a simple ytterbocene complex was used for the first time in the ring-opening polymerisation of cyclic phosphoesters. The polymerisation is applicable to both cyclic phosphonates and cyclic phosphates, giving corresponding biodegradable polyphosphoesters with a medium to high molar mass and low molecular weight distribution. NMR and MALDI-TOF investigations indicate that the polymerisation follows a ring-opening chain polymerisation mechanism, allowing the preparation of both homopolymers and block copolymers.