CAREER: Toward Photocontrol of Conjugated Polymer Emission: Modulation of Fluorescence Properties in Photochromic Poly(p-phenylenevinylene) Derivatives

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With the support of the Organic and Macromolecular Chemistry Program in the Chemistry Division, Professor Elizabeth J. Harbron of the College of William and Mary will develop photoluminescent (PL) polymers whose fluorescence and emission color can be modulated by light-activated isomerization of pendant groups. Potential suggested applications for these materials include photo switching and memory storage. Several new photochromic poly (p-phenylenevinylene) (PPV) derivatives will be synthesized and studied in solution and film. The first area of investigation will be a derivative in which energy transfer from the polymer backbone occurs selectively to only one form of the pendant photochrome. Thus, PPV will emit with unquenched intensity when the photochrome is in one form and will not emit when the photochrome is in its resonant form due to efficient energy transfer. This polymer will facilitate true on/off reading of a fluorescence signal and will also enable all-optical write/read/erase cycles in polymer films. Additional studies will focus on control of emission intensity through photoinduced photochrome alignment, which will be studied on the single molecule level. Time-resolved fluorescence techniques will be employed to study all photochromic PPV derivatives to investigate the interplay between exciton migration within the PPV chain and energy transfer to pendant photochromic acceptors. The results of measurements with different photochromic side chains will be used to identify the combination of PPV and side chain energetic characteristics required for an optimal photoswitch polymer.. With the support of this CAREER award from the Organic and Macromolecular Chemistry Program, Professor Harbron will work with materials that are simple, and synthetically accessible to provide a fundamental understanding of the processes involved in switching phenomena with the real benefit being provided by the optical measurements and experiments. Broader impacts of the proposed activity are primarily the training of undergraduates in polymers, organic synthesis, and photophysics. Professor Harbron will continue getting undergraduate researchers involved in projects and in publishing in ACS journals. She has also proposed summer course for high school students.