New initiators for the ring-opening polymerization of cyclic esters

The application of new initiators, based on the lanthanide elements, for the ring-opening polymerization of cyclic esters, has markedly improved the potential for producing precisely controlled polymers from these monomers. A wide variety of complex macromolecular architectures containing polyester chains have been prepared using these initiators. Decisive factors in achieving this are the range of monomers that can be polymerized, and the favourable rates of polymerization obtained for these monomers. The number of papers dealing with the exciting synthetic aspects of these initiators is rapidly increasing. In this review, a perspective of the developments in this area is presented.