Dynamic Multi-state Living Coordination Polymerization for Next Generation Polyolefins

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With the support of the Chemical Catalysis (CAT) and the Macromolecular, Supramolecular, and Nanochemistry (MSN) Programs in the Division of Chemistry, Professor Lawrence Sita of the University of Maryland, College Park is developing new polymerization catalysts that can be programmed to deliver multiple products from a single initiator. This ‘one catalyst – many materials’ paradigm is being investigated to expand the range of new polyolefin materials that possess technologically-useful physical properties that are of benefit to society and the economy, such as recyclability and serving as replacements for less environmentally benign legacy plastics. Group 4 catalysts are being tuned to undergo selective polymerization in systems that would typically be assumed to be unselective. The activities that are being pursued also provide an excellent forum for training the next generation of scientists for science- and engineering-related careers in education, industry, and science policy, and importantly, those who are members of underrepresented groups.Homogeneous olefin polymerization catalysts are traditionally optimized to produce a single type of polymer from a single monomer. In contrast, Professor Sita and his research team are designing and preparing Group 4 d(0)-complexes supported by cyclopentadienyl and amidinate ligands that can serve as initiators for the living coordinative chain transfer polymerization of olefins into multiple new classes of polyolefin products. By exerting control over the relative rates of reversible dynamic reactions that are competitive with chain-growth propagation, highly versatile multi-state polymerization processes are being programmed to deliver a spectrum of different products from a single initiator under otherwise identical conditions. Different controlling elements of the system being explored include: the structure and chirality of the amidinate ligands, the effect of coordinative groups installed on the amidinate ligands, as well as reaction mixture temporal control over polymer composition. These studies are working towards the advance of polyolefin materials with desirable physical properties while establishing new elements of catalytic control in complex systems.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.