Conjugated polymer - liquid crystal solutions: dynamic control of intramolecular energy transfer in the end-capped poly-(p-phenylene-ethynylenes)

ORGN 434

Evgueni E. Nesterov, Zhengguo Zhu, and Timothy M. Swager. Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139

The application of conjugated polymer based electro-optical devices and sensors strongly depends on the efficient photoexcitation energy migration through the polymer chain. The ability to control the energy transfer using external stimuli is important not only for design of new molecular devices but may also improve our understanding of the mechanism of this process. Here we report synthesis and study of the anthracene-capped poly-(p-phenylene-ethynylenes) (PPEs), e.g. polymer 1. The anthracene units act as band gap lowering energy traps facilitating the efficient excitation energy funneling from PPE chain towards the termini. Thus, photoirradiation of the polymer 1 leads to the fluorescent emission both from the PPE chain and from the anthracene units. Dissolving of the polymer in common nematic liquid crystals (LCs) enhances the efficiency of the energy migration due to improving polymer alignment and increasing overall intra-chain conjugation. More importantly, the LC solution may be used to control the extent of the energy migration through the polymer by applying external electric field. Depending on frequency of the electric field, the extent of the energy migration towards the end groups can be finely tuned, which results in a substantial change in the ratio of emission from the PPE chain and anthracene termini. This phenomenon may be employed in the design of new electro-optic materials. Possible variations of the polymer structure to improve the electro-optic response as well as photophysical study of these systems will be discussed.

Physical Organic, Materials, Heterocycles, Aromatics, Metal-Mediated Reactions 8:00 PM-10:00 PM, Tuesday, September 9, 2003 Hilton New York -- Americas Hall 1, Poster Division of Organic Chemistry The 226th ACS National Meeting, New York, NY, September 7-11, 2003