CAS: Augmenting the Applicability and Sustainability of Direct Arylation Polymerization (DArP)

University Of Southern California, Los Angeles CA

Investigators

Abstract

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Professor Barry C. Thompson of the University of Southern California is studying green and energy efficient methods to prepare conjugated polymers. This class of organic semiconductors has shown a great promise for a diverse array of optoelectronic applications, such as sensors, solar cells and light emitting diodes. In this research, systematic studies will be conducted in order to enhance the sustainability of direct arylation polymerization, a controlled and atom-economical method to synthesize conjugated polymers. Strong emphasis will be placed on mechanistic understanding of this catalytic process in green solvents and development of rational methods for engendering functional group tolerance. The combination of these two approaches has the potential to transform the sustainability, accessibility and scalability of conjugated polymers. In the long run, this could lead to practical large-scale production of polymers with previously inaccessible molecular structures and properties. Broader impacts of this work will be demonstrated through integrated set of activities. Participation in the University of Southern California-Cerritos Community College Internship Program will entail hosting community college students, providing an effective way to engage primarily under-represented groups. This internship program will be extended to involve students from Los Angeles Pierce College, an HACU Member Hispanic Serving Institution. Additionally, a pioneering program focused on Write-to-Learn pedagogies to facilitate student learning and retention in undergraduate science classes will be developed. While the rapidly increasing performance of applications of conjugated polymers (CPs) has brought increased attention to the field, current synthetic approaches have lagged behind what is required for continuing discoveries and the increasing focus on sustainable processes and materials in synthetic polymer chemistry. This project will focus on addressing deficiencies in direct arylation polymerization (DArP), with the potential to transform this polymerization into a controlled, sustainable, scalable, and broad-scope method for preparing CPs. In the first objective, mechanistic features of DArP will be investigated in dihydrolevoglucosenone, a bio-based solvent derived from cellulose and classified as an alternative to dimethylformamide. Other green methods for the polymerization will involve heterogenous emulsion polymerization, use of earth-abundant metals for catalysis, and lowering of reaction temperature. The second objective will explore strategies to achieve controlled chain-growth in DArP by transcribing catalyst-transfer direct arylation conditions to polymerizations using a fluorene-tetrafluorobenzene monomer and a variety of halogenated aromatics as the initiators. The third objective targets reaction conditions to increase the functional group tolerance of DArP. This is to be achieved by focusing on CPs bearing acidic/reactive and palladium-coordinating functional groups. The broad scope of sustainable approaches outlined in this research has the potential to provide advances that can contribute to more sustainable chain-growth polymerization processes in general. 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.