Designing Complexes for Homogenous Catalysis and Polymerization

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This research program combines synthetic inorganic chemistry, catalysis and polymerization to address problems concerning the use of abundant CO2 as a feedstock molecule for preparing more valuable chemicals, including polymers. The work involves fundamental research but with significant applications relevant to society. The primary goal is the preparation of new metal-containing molecules that catalyze the reaction of CO2 with other small molecules in a controlled fashion. The products of these reactions can be used as solvents, precursors to other value-added chemicals or high performance polymers.***Ultimately, can CO2 be combined with other waste molecules to give valuable products? For example, propylene oxide (PO) can be obtained from propene, which is a byproduct of oil refining and natural gas processing. CO2 can be reacted with PO to give propylene carbonate or poly(propylene carbonate). Propylene carbonate is used as a polar solvent with a high boiling point and as a component of electrolytes in lithium batteries. Polymers such as poly(propylene carbonate) are useful as degradable thin films or as components in polyurethane manufacturing for things like automotive seat cushions. Other reactants can be sourced from plant matter such as citrus fruit peels (limonene oxide) or forestry waste (pinene oxide). Previous work focused on tunable catalyst systems that can be rationally altered to dial in selectivity for cyclic or polymeric carbonates. With these systems in hand, interest now lies in the control of polymer molecular weight and microstructure. Microstructure concerns the arrangement of the monomers within the polymer (e.g head-to-tail or head-to-head orientation, known as regiochemistry, and up or down relative arrangement of the monomer groups, known as tacticity). Microstructure has significant influence on the physical properties of the polymer, like melting point and crystallinity and its crucial control will be obtained through careful catalyst design. New generations of catalysts based on inexpensive and earth abundant metals (e.g. chromium, cobalt, iron, aluminum, magnesium and zinc) will be prepared. Computational studies will assist with insight into mechanistic details, partnered with direct experimental evidence obtained by in-situ spectroscopy performed using a custom designed reaction vessel, as well as by a variety of mass spectrometry techniques. This information will permit the further tuning of experimental conditions and catalyst design. ***Long-term goals include the development of new catalytic systems and useful materials derived from CO2, as well as contributing to the fundamental knowledge of reactions of CO2 and the chemistry of earth abundant metals. Both of these goals are extremely valuable for developing sustainable technologies and efficient use of resources for the manufacturing industry in Canada.