Reimagining the Platform for Semiconducting Polymers

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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 developing a new class of semiconducting polymers by decorating commodity plastics with electro-active segments. Semiconducting polymers impact many areas of contemporary energy and electrical science. These long chain carbon-based macromolecules are extensively used in solar cells, LED screens and other applications that utilize the conversion of electricity to light. In this research, electro-active segments will be attached to main polymer backbone consisting of single carbon-carbon bonds with a specific alignment relative to one another. Segments will be prepared that contain small organic molecules featuring carbon-nitrogen pi-bonds (double bonds). When these pi-bonds are broken, they create positive and negative charges along the side chains of the main polymer backbone. With such a chemical approach, non-metallic plastics are converted to plastics that conduct electricity and absorb light. If successful, this work will fundamentally change the approach toward electro-active polymers with improved environmental stability and mechanical properties. This work will provide an outstanding framework for the training of undergraduate and graduate students in polymer chemistry. Outreach and educational activities will focus on participation in the USC-Cerritos Community College summer research internship program and implementation of writing-to-learn pedagogies in undergraduate organic chemistry courses. There is also broader impact through international collaboration with the collaborators in Germany adding a special dimension to the training experience for the students engaged in this research. This research will focus on development of semiconducting polymers based on non-conjugated (meth)acrylate backbones containing electronically active pendant groups. In the first specific aim, the synthesis of homopolymers will be optimized using controlled radical and anionic polymerization methods, with the goal to identify the influence of critical aspects of polymer structure on charge transport with a central focus on the role of stereoregularity. Post-polymerization methods to incorporate electroactive pendants will utilize transesterification and thiol-ene addition reactions. The second aim focuses on stereoregular block copolymers based on acrylate backbones. Lastly, the prepared multi-functional polymers will be explored for potential use in organic photovoltaics by evaluating the correlations between polymer structure and thin film morphology. The proposed research, if successful, will advance fundamental chemistry knowledge on how to use tacticity to assist in the arrangement of the electro-active pendants into an ordered conformation to facilitate and improve electron transport efficiency. In the long run, this work could also enable the preparation of flexible, lightweight and inexpensive organic semiconductors with roll-to-roll processing.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.