Catalysis plays a central role in the activation and use of renewable resources in polymer synthesis.1 Here, the renewable resources of interest include plant-derived monomers and the use of carbon dioxide as a raw material. The lecture will highlight recent work developing homogeneous metal complexes, featuring zinc/magnesium and first row transition metals for use in polymerization catalysis. In particular, discoveries that activity and selectivity are enhanced by controlling the ligand conformation and by the use of synergy in heterodinuclear catalysts will be highlighted.2-3
We have recently reported a series of catalysts that can selectively polymerize mixtures of monomers to deliver block sequence controlled copolymers.4-5 Key to the ability to selectively enchain from mixtures is the ability to switch the catalyst between different polymerization cycles/mechanisms (Fig. 1). Using this method, mixtures of epoxides/lactones/anhydrides and carbon dioxide are selectively enchained to provide multi-block copolymers. Central to the unusual performance of these catalysts is control over the inorganic chemistry of the metal-polymer chain end-group so as to switch and direct particular (block) polymer enchainment sequences. The catalyst syntheses, characterization and application data will be presented, including in situ spectroscopic and DFT studies. The catalysis allows the preparation of new block and alternating copolymers and their properties as degradable elastomers, shape memory polymers and specialty materials will be highlighted.
Figure 1 Switchable Catalysis from monomer mixtures (LHS) and synergy in heterodinuclear catalysis (RHS)
- Zhu, Y.; Romain, C.; Williams, C. K. Nature 2016, 540, 354.
- Thevenon, A.; Romain, C.; Bennington, M. S.; White, A. J. P.; Davidson, H. J.; Brooker, S.; Williams, C. K. Angew. Chem. Int Ed. 2016, 55, 8680.
- Garden, J. A.; Saini, P. K.; Williams, C. K. J. Am. Chem. Soc. 2015, 137, 15078.
- Romain, C.; Zhu, Y.; Dingwall, P.; Paul, S.; Rzepa, H. S.; Buchard, A.; Williams, C. K. J. Am. Chem. Soc. 2016, 138, 4120.
- Zhu, Y.; Romain, C.; Williams, C. K. J. Am. Chem. Soc. 2015, 137, 12179.