CAREER: Optically-Controlled Phase Transition of Organic Molecules via Molecular Switching

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NON-TECHNICAL SUMMARYLight-responsive molecules have emerged as a new tool to optically control various properties of solid-state materials. Reversible control over the optical, thermal, phase, and mechanical properties of solid-state materials enables applications that involve optical storage, energy storage, and mechanical response. The fundamental understanding of the optically-induced molecular transformation in solids and how such transformation results in phase change, however, is currently lacking. This CAREER research project, jointly supported by the Solid State and Materials Chemistry program in the Division of Materials Research and the Chemical Structure, Dynamics, and Mechanisms B program in the Division of Chemistry, broadens the knowledge on light-molecule interactions in a condensed environment, which is translated to understand solar thermal energy storage that has a tremendous impact on the energy security of the nation. The project contributes to the advancement of various fields studying molecular switching, phase transition behaviors, and renewable solar energy storage. Additionally, it addresses critical areas for improving underrepresented minority engagement in STEM at Brandeis University and in the local community. Undergraduate students from underrepresented groups are actively recruited and trained in organic materials chemistry, and Spanish-English bilingual science events are established in partnership with a local high school to promote the interests of students in chemistry and renewable energy technologies.TECHNICAL SUMMARYWith this research project organic materials that are optically stimulated to undergo reversible phase transitions between solid and liquid are developed. The principal investigator and her research group design and synthesize new organic functional materials that harness the optically-induced conformational and polarity change of photoswitches to control the phase of bulk materials. Various photochromic core structures and functional groups are explored to yield a deep understanding of the structure-property relationship. New functionalization strategies that delineate the effect of the polarity, steric hindrance, molecular symmetry, and fluorous interactions on the condense-phase photoswitching and consequent phase transitions are investigated. Through this work, molecular switching dynamics in a crowded environment are unraveled, and strategies to alter the conformational freedom around the moving parts of molecular switches are developed. Additionally, measurements of thermal parameters of phase transition materials are used as a characterization tool to understand the types and degree of intermolecular interactions in condensed phases.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.