Pendant Photochromic Switches Enabling Fluxional Macromolecular Pi-Electronics

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With this award, the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry is funding Professors John D. Tovar and Arthur E. Bragg of the Department of Chemistry at Johns Hopkins University to understand how pi-conjugated building blocks with fluxional electronic structures driven by light absorption can tune the properties of organic electronic materials. Organic electronics can impact many areas of contemporary energy and electrical science, with innovations on the horizon in fields such as large-area lighting, energy storage, and even biomedicine. These materials are essentially long chain plastic-like molecules but with unusual electronic properties imparted through special bonds called pi-bonds. The alternation of pi-bonds with single bonds enables the molecules or polymers to conduct electricity when these bonds are varied. In this research, the investigators first construct molecular building blocks for the polymers with different electronic properties. Computational modelling is utilized to systematically investigate how chemical changes introduced into the building blocks affect the overall properties of the polymers from which they are formed. Advanced spectroscopic and electrical measurement techniques are used to understand changes in electronic and molecular structures in real time. Such systematic investigations generate knowledge that could lead to significant improvements in cutting-edge applications ranging from high-speed transistors to energy storage. Students associated with this project are exposed to interdisciplinary research and prepared to be leaders in the next generation of interdisciplinary scientists. Education and outreach activities targeting students and underrepresented minority groups in urban Baltimore high schools provide additional creative opportunities for broader community involvement.This work is focused on the exploration of organic electronic materials derived from complex aromatic structures as components of photoswitchable conjugated polymers. The research plan involves the synthesis of photoswitchable fluxional monomer units triggered by various external stimuli and extensions to oligomeric and polymeric analogues, computational modeling to understand how these chemical changes impact electronic properties, and spectroscopic interrogations using steady-state and ultrafast or other time-resolved techniques to capture changes in electronic and molecular structure. The general research approach is primarily concerned with new strategies to achieve highly polarizable polymer electronic structures as opposed to particular bandgap engineering of energy levels. The ideas elucidated from this project could be transitioned to many types of application-specific materials designs such as stimuli-switchable transistors whereby conjugation pathways can be controlled externally.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.