11.16 - Main Group Complexes in Polymer Synthesis

Main group compounds have been fundamental to polymer synthesis since its earliest days, with reports of ring-opening polymerization mediated by s-block systems from even the mid-19th century. This important field continues apace, fuelled increasingly by the need for sustainable polymers derived from renewable sources, and for polymers which are degradable under appropriate conditions to obviate waste-stream derived issues. In this chapter, main group complexes for ring-opening polymerization of a wide range of cyclic organic monomers are summarized. The chapter opens with a brief overview of mechanistic steps which main group catalysts can initiate for ring opening polymerization. This is followed by consideration of systems for the polymerization of cyclic ethers and thioethers; acetals; esters and thioesters; amides; and carbonates and thiocarbonates, with a brief description of monomers and polymers and a non-comprehensive overview of s- and p-block complexes as initiators for each monomer. There is then discussion of ring-opening copolymerization approaches, specifically focusing on alternating copolymers and the inclusion of carbon dioxide as a C1 feedstock in these reactions. Finally, main group catalysts for the degradation of ROP-derived polyesters are discussed. Approaches to return virgin monomer stocks for repolymerization in a circular economy context are discussed as well as waste valorisation by transesterification to yield higher value decomposition products from ROP-derived sustainable polymers, with brief discussion of mechanisms that may be operant in these steps.