Abstract
The design of new catalysts for the polymerization of cyclic esters derived from biorenewable resources is an important component of broader efforts to develop sustainable technologies for replacing petroleum-based polymeric materials. i-iv Thorough understanding of polymerization mechanisms plays a key role in catalyst design efforts, yet while rudimentary aspects of cyclic polymerization pathways are well-recognized, many details remain unclear. v,vi Included among the varied mechanistic issues under study are the bases for observed stereoselectivities in metal-catalyzed lactide (LA) ring-opening polymerizations (ROPs), the nature of the catalytic species involved in ROPs, supporting ligand electronic and steric influences on ROP rates, and the relative contributions and characteristics of coordinative insertion and monomer activated pathways (Figure 1). vii-x We seek to address such issues through the detailed mechanistic analysis of ROP catalysts of variable types, and report here the results of studies of a range of systems, including those shown in Figure 2.