CAS: Lewis Pair Catalyst Platform for Functional Polyether Synthesis

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With this award, the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry is funding Professor Nathaniel Lynd of the Department of Chemistry at the University of Texas at Austin to develop new polymerization techniques for the controlled synthesis of polyethers. Polyethers are a class of large molecules in which every repeating unit contains a carbon-oxygen bond. They are typically prepared from small cyclic carbon-oxygen containing compounds called epoxides. This class of polymers is becoming increasingly important in today’s society because they are easier to degrade pathways than widely used plastics that contain mostly carbon-carbon bonds along the main polymer chains. Hence, polyethers might provide a viable solution to the recyclability problem which is of vital importance from an environmental perspective. In this research, catalysts based on aluminum are systematically designed to speed up the synthesis. The new chemical reactions are simple and can be transferred to laboratories around the world, which could greatly expand access to these types of polymers. This research is having a broader impact by providing education and research training to a diverse population of undergraduate and graduate students. Additional outreach efforts are focused on interactions with students from the Austin School for the Deaf and K-8 students through on-campus introductions to polymer chemistry at the Introduce a Girl to Engineering Day at the University of Texas-Austin. This research is focused on development of Lewis pair catalyst systems for functional polyether synthesis. There is currently no consensus polymerization technique available for polyethers that provides access to polymers with controlled molecular weights, chain-end functionality, good tolerance to monomer functionality, and availability to the non-specialist. This research seeks to further the development of such a tool by exploring the kinetics and mechanisms of the N-Al Lewis pair catalysts. Steric and electronic factors that govern Lewis-pair catalyst activity for epoxide polymerization are systematically explored. Detailed studies associated with Lewis pair formation and structure are also conducted. Special emphasis is placed on the investigation and elimination of parasitic initiation/termination through decomposition of a zwitterionic intermediate resulting in alkyl, or hydride terminal polymers, and/or undesirable cyclization. The methodology associated with this work introduces a readily available polymerization platform requiring only mixing of two commercially available chemicals. As such, it opens doors to new chemists with limited technical or infrastructural means to convert structurally diverse epoxides into functional and useful polymers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.