NCI

Exploiting Non-Covalent Interactions (NCI) in polymerisation catalysis

Non-covalent interactions (NCIs) encompass a wide range of interactions, including ion pairing, hydrogen bonding, dipole-dipole interactions, π-π stacking, hydrophobic interactions, and van der Waals forces.

There has been growing interest in harnessing NCIs in both organo- and metal-catalysed systems to enhance catalyst activity and selectivity. Various approaches have been developed to modify the first and second coordination spheres through ligand-substrate interactions, ligand-ligand interactions, and more sophisticated scenarios involving multiple interactions.

Our group is interested in translating these strategies to metal-catalysed polymerisation catalysis, not only to improve catalyst activity and selectivity but also to enable the polymerisation of challenging monomers, such as those with low ceiling temperatures.

To date, we have reported two complementary strategies.

The first employs catam aluminium catalysts, exploiting the cooperative role of the NH moieties within the catam ligand scaffold. This approach combines elements of organocatalysis and metal-based catalysis to enhance polymerisation performance.

Our second strategy involves the in situ formation of heterobimetallic species through the control of cation-π interactions between the phenolate moieties of salen-based titanium catalysts and silver salts. This enables the modulation of catalyst behaviour through secondary-sphere interactions.

For more details, check out our recent publications.

Publications

  1. Gesslbauer, S.; Savela, R.; Chen, Y.; White, A. J. P.; Romain, C. Exploiting Noncovalent Interactions for Room-Temperature Heteroselective rac-Lactide Polymerization Using Aluminum Catalysts. ACS Catal. 2019, 9, 7912–7920. 10.1021/acscatal.9b00875
  2. Baker, C. A.; Romain, C.; Long, N. J. Cationic-π Interactions enabling Hard/Soft Ti/Ag Heterobimetallic Cooperativity in Lactide Ring-Opening Polymerisation. Chem. Commun. 2021, 57, 12524–12527. 10.1039/D1CC05083D
  3. Koh, J.; Baker, C. A.; Diamantakis, M. N.; Long, N. J.; Romain, C. A pinch of silver salt to enable rac-lactide ring-opening polymerisation at room temperature using Ti-salen complexes. Polym. Chem. 2025, 16, 1503–1508. 10.1039/D4PY01319K