Cultivating Conjugated Polymers as Novel Light Responsive Materials

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NON-TECHNICAL SUMMARY:Stimuli-responsive materials alter their structure or properties according to changes in their environment. This research program will develop novel stimuli-responsive polymers whose function and properties can be controlled by light exposure. This is exciting as light is a "clean" stimulus in that it can be applied remotely without physical contact, is readily patternable, and its intensity can be tuned with great fidelity. Unfortunately, there are few compounds that are light-responsive. The planned research program will provide pathways to direct these structural changes to improve their performance in functional devices and to amplify these structural changes. The results of this research program will therefore expand the applications that can be rationally controlled and patterned by light exposure, which will significantly extend the practicality of light-responsive materials. Workforce development and training of the next generation of scientists and engineers who are prepared to tackle the grand challenges in stimuli-responsive materials will be realized through this research program and also by engaging public high school students in hands-on research experiences, thus providing exceptional preparation for college. Further impact will result from the completion of experiments at the national neutron facilities at ORNL and NIST where the students participating in this project will acquire hands-on experience in a multi-user facility and contribute to the continued health of these national resources. This project will also further develop the sustainable research infrastructure in Tennessee and will be implemented to promote the participation of underrepresented groups in research.TECHNICAL SUMMARY:The overarching goal of this research program is to provide pathways to rationally control the optoelectronic performance of conjugated polymers by altering their molecular, nanoscale, and mesoscale structure with exposure to light, as well as to provide robust routes to amplify their light-induced structural changes so as to realize novel light-responsive materials. Current results clearly show that the absorption of a photon by conjugated polymers reversibly alters their structure, assembly, and functionality. Therefore, this research program will elucidate the relationship between light-induced structural order in conjugated polymeric active layers and their photo-physical properties. In parallel, targeted conjugated polymer constructs that are designed to augment their alteration in structure and assembly when exposed to light in solutions and thin films will be developed and harnessed to provide routes to new stimuli-responsive materials with desired properties. This research program will develop methods to amplify the structural changes of conjugated polymers with exposure to light and correlate light-induced alteration of the hierarchical structure of conjugated-polymer mixtures to optimal functional response. This critical information will then be used to elucidate guidelines to enable the systematic modification, rational design and control of novel light-responsive materials with targeted properties. This research will also attempt to directly correlate the impact of photon absorption on conjugated polymer configuration, assembly, and vertical morphology to the optoelectronic performance of conjugated polymer active layers. This in turn may further provide crucial links toward the rational design of conjugated polymer solutions or blends and associated thermal, light, and deposition processing protocols so as to realize devices with optimal functional performance.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.