CAREER: Effect of Electric Fields on the Miscibility of Polymer Blends and Block Copolymers

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TECHNICAL SUMMARY:A major materials science objective at present is to create nanostructured morphologies of different blend components. For example, it is believed that the efficiency of ion and exciton conduction in energy related applications such as batteries and solar cells may be optimized by adjusting the morphology of the nanometer-sized polymer domains to form conducting pathways or channels. One route to such ideal morphologies is through alignment of microdomains via the application of electric fields, particularly advantageous for these applications where electrodes are already part of the device. Currently there is still limited understanding of how the presence of electric fields affects the miscibility of polymer blends and block copolymers. In particular, what is the free energy contribution to mixing caused by the presence of an electric field? Theory of this phenomenon is limited by a lack of unambiguous experimental data characterizing the shifts in miscibility with electric fields, which can be quite large, up to 50 K decrease in the phase separation temperature for field strengths around 10 V/micrometer. The proposed research will use fluorescence to measure the phase separation temperature of polymer blends and the order-disorder transition temperature of block copolymers as a function of composition in the presence of electric fields. The experimental results will be fit to a modified Flory-Huggins expression to ascertain the free energy contribution to mixing caused by the presence of an electric field. These results will provide improved fundamental understanding of the polymer-polymer interactions that control miscibility and a means to locally tune and control the enthalpic interaction of a blend. NON-TECHNICAL SUMMARY:Use of polymers in technologically advanced applications is widespread, with many of these applications using multiple polymer components arranged into nanometer-sized domains. The alignment of these domains could be optimized by the application of electric fields across the existing electrodes of the device. The PI will develop a fundamental understanding of how the presence of electric fields affects the blending interactions in polymers, a phenomenon which is currently not understood. The educational component will develop a network of mentoring resources for practical career advice. The centerpiece will be a web-based discussion forum where students of all ages and walks of life can exchange advice on potential career plans and first-hand experience in ways of accomplishing their goals. Such a venue will help fill a void in practical career information that is currently lacking. This is especially important for students from economically limited backgrounds, most frequently from underrepresented minorities, who typically do not have relatives or family friends in related careers that can provide the needed guidance. The PI will directly motivate students at a range of levels about career opportunities, taking groups of graduate and undergraduate students to visit local public schools to share their aspirations about careers in science and technology.