Dr. Sharani Roy of the University of Tennessee-Knoxville

Professor Sharani Roy of the University of Tennessee-Knoxville will present

"Modulating polyethylene microstructure using a redox-switchable polymerization catalyst: a computational mechanistic study"

on May 1, 2019 at 4:10pm in Neville Hall, Room 3

Developing accurate, first-principles-based models of catalytic mechanisms can help to elucidate reaction pathways and design next-generation catalysts. This work investigates the mechanism of tunable ethylene polymerization by a redox-switchable nickel-diimine catalyst using density functional theory. This nickel- based Brookhart-type catalyst, developed by the group of Brian Long at the University of Tennessee, contains the dipp-BIAN α-diimine ligand. This redox-active ligand gives the catalyst the ability to change its redox state in the presence of a reducing agent, such as cobaltocene. Experimental results by the Long group showed that the reduced form of the catalyst produces a less branched polyethylene than the non- reduced form the catalyst, demonstrating that the microstructure and properties of the polyethylene product can be tuned just by changing the electronic state of the catalyst, while keeping other reaction conditions the same. Our computation of the reaction pathways for both the non-reduced and reduced forms of the catalyst explains how reduction of the catalyst produces a more linear polyethylene. Further, we propose candidates for redox-switchable catalysts related to the studied complex that can further modulate the microstructure of polyethylene.