Design, Synthesis and Investigation of Substitution on Conformation Properties

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In this project, funded by the Chemical Structure, Dynamics & Mechanisms-B Program of the Chemistry Division, Professor Jennifer Lu at University of California, Merced, is developing a new class of molecular switches that can be triggered by low-energy stimuli. Inspired by long-lasting and precise changes in the shapes of biomolecules, Professor Lu designs and synthesizes a set of unique molecular structures and studies their changing structures. The multidisciplinary nature of this project employs fundamental knowledge from organic chemistry, physical chemistry and materials science and engineering, and provides a learning environment that is conducive to training and inspiring students at all levels. A key component of the education program involves outreach to encourage high school students to pursue college education in STEM fields. This research may help scientists understand the directional growth of a plant in response to sunlight and how to harvest waste energy. Professor Lu and her research group develope polymers that generate anomalously large thermal contractions (up to -2300 ppm/K). These polymers contain a small amount of 1, 4, 7, 10 tetra-phenylamide substituted s-dibenzocyclooctadiene (DBCOD), a flexible cyclooctane group fused to one rigid phenyl ring at each end. The research group hypothesizes that this thermal contraction stems from DBCOD's conformational up-conversion from the global minimum to a local minimum. The relative energies of these two conformers and the energy barriers of this conformational transition can be adjusted by the local environment (e.g., substitution type and pattern). To acquire a fundamental understanding of substituent effects on the thermodynamic and kinetic aspects of the DBCOD conformational change, they conduct a multidisciplinary investigation that involves computation-guided model system synthesis and atomic and molecular scale characterizations. The goal of this project is to establish substitution design rules that correlate specific substituents to their effects on conformation properties. To connect atomic-scale changes to macroscopic behavior and validate the design guideline, they use the DBCOD derivative that favors the twist-boat conformation at lower temperature and the chair conformation at higher temperature to make a linear polymer.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.