Advancing the Performance and Capabilities of Direct Arylation Polymerization (DArP)

University Of Southern California, Los Angeles CA

Investigators

Abstract

With this award, the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry is funding Dr. Barry C. Thompson from the University of Southern California to develop green and energy efficient methods to produce semiconducting polymers. This existing class of plastic-electronic materials has shown great promise for use in organic solar cells and light emitting diodes, as well as several sensory applications in which light is converted to electrical current. In this work, semiconducting polymers are prepared using catalysts based on inexpensive and abundant elements such as copper and nickel. These metals are utilized to lower the energy barrier associated with polymerization processes, making it easier to convert starting materials to desired products. Consequently, their use improves the sustainability of semiconducting polymers and enables new reactivity and properties in the polymers. The new processes associated with this award provide means to assemble the repeating monomer units along main polymer chains in several different ways giving rise not only to linear chains composed of identical repeating units, but also chains in which those repeating units are different and arranged in controlled and predictable ways. Consequently, access to such advanced architectures in these polymers could lead to improvements in their applications, specifically the efficiency by which they convert sunlight into electricity. The work enables outstanding training for undergraduate and graduate students in polymer chemistry, extending to students hosted at the University of Southern California from Cerritos Community College. The broad impact through the development of a graduate student exchange program with Ludwig Maximillians University in Munich, Germany is very important for helping to expose students to the broader scope of international research and collaboration. This research is focused on the development of alternative synthetic routes to direct arylation polymerization catalyzed by copper and nickel complexes for the synthesis of conjugated, semiconducting polymers. Special emphasis is also placed on the use of green and environmentally friendly solvents. The capabilities of direct arylation polymerization are extended by focusing toward a transition from step-growth to chain-growth, which enables access to more advanced architectures such as block and gradient copolymers. Studies related to the ability of direct arylation polymerization to effect controlled living polymerization are a significant step forward in this area of research because it would enable control over the molecular weight and polymer polydispersity. An additional direction involves exploration of more sustainable oxidants for the related dehydrogenative polymerization process that avoids monomer halogenation and the use of stoichiometric amounts of silver oxidants. The use of earth-abundant copper and nickel catalysts to access conjugated polymers via this work is important and has the potential to significantly reduce the cost and complexity of existing procedures for conjugated polymer synthesis, which are generally not atom efficient, require harsh reaction conditions, toxic solvents, and create significant amounts of waste products. 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.