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  • The central reaction step in the complicated copolymerization involves a mixed alkoxide/carboxylate species and that side reactions likely are due to shunting of this species to another one with two alkoxides.
    10/09/17

    Collaboration yields insights into copolymerization for synthesis of new polyesters

An extensive collaboration within the Center for Sustainable Polymers (CSP), and involving other University of Minnesota (UMN) centers as well, is yielding important insights into the alternating copolymerization of epoxides and anyhdrides for the synthesis of new polyesters.

In a paper, “Mechanistic Insights into the Alternating Copolymerization of Epoxides and Cyclic Anhydrides Using a (Salph)AlCl and Iminium Salt Catalytic System,” published in the Journal of the American Chemical Society, the results of work that follows from previous development of catalysts for the copolymerization of epoxides and anhydrides by the Professor Geoffrey Coates research group are described. The reaction yields useful polyesters, including sustainable ones that are derived from renewable starting materials, but the process can be sluggish and can suffer from undesirable side reactions. 

With the ultimate goal of improving the previously developed catalysts and finding ways to avoid the side reactions, detailed kinetic and mechanistic experimental studies using multiple methods were performed collaboratively by researchers in the Coates group at Cornell and the Professor William Tolman group at UMN, with complementary computational work by the Professor Christopher Cramer group at UMN. The team elucidated many details of the complicated copolymerization, with key findings being that the central reaction step involves a mixed alkoxide/carboxylate species and that side reactions likely are due to shunting of this species to another one with two alkoxides. Critically, the new mechanistic insights suggest creative new ways to enhance the reaction rate and avoid the side reactions, opening new doors for innovations in the synthesis and ultimate use of sustainable polymers. 

“By bringing together disparate expertise and multiple perspectives under the umbrella of the CSP, we obtained a new understanding of a quite complicated reaction system that would have been difficult, if not impossible, to obtain otherwise. Indeed, this work exemplifies how true multidisciplinary collaboration within a center can lead to deep insights and innovative discoveries,” said Tolman.

This research involved the University of Minnesota’s Department of Chemistry, CSP, Chemical Theory Center, Minnesota Supercomputing Institute, and Department of Chemistry & Chemical Biology from the Baker Laboratory at Cornell University. Student and post-doctoral researchers working with the principal investigators on this research were Megan Fieser, Ph.D., Marie Sanford, Ph.D., Lauren Mitchell, Ph.D., Christine Dunbar, Ph.D., graduate student Mukunda Mandal, and Nathan Van Zee, Ph.D., as well as undergraduate student Devon Urness.

CSP Director Marc Hillmyer said, “Synergy is a defining characteristic of the work in the Center for Sustainable Polymers and this study shows how integration of expertise in three different laboratories can lead to breakthroughs that allow for significant advances in the field."

Researchers include Lauren Mitchell, Megan Fieser, Christine Dunbar, Maria Sanford, and Mukunda Mandal.
Researchers include Lauren Mitchell, Megan Fieser, Christine Dunbar, Maria Sanford, and Mukunda Mandal.