A variety of strategies have been explored to obtain active olefin polymerization catalysts, including the use of steric protection, hydrogen bonding, fluorine bonding, and dinuclear active sites. The Do laboratory is investigating the application of pendant Lewis acids to facilitate the coordination-insertion of polar and non-polar olefins into nickel-alkyl complexes. Our prototype system features nickel phenoxyimine complexes appended with polyethylene glycol (PEG) chains to the ligand framework. The PEG groups allow the installation of alkali cations (Li+, Na+, and K+) adjacent to the active nickel centers. We show in ethylene polymerization studies that the alkali ions alter the reactivity of the nickel catalysts, affecting catalyst activity, polymer branching, and polymer molecular weight. We also report results on using our heterobimetallic catalysts to copolymerize ethylene with either α-olefins or polar olefins. Finally, we will discuss the implications of our catalyst design and how we can apply the knowledge that we’ve gained to develop better and improved generations of olefin polymerization catalysts.

Alkali cations as leading actors in olefin polymerization catalysis

253rd National Meeting (2017)

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