Connecting Short Range Order to Macroscopic Properties in Complex Structured Fluids

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Non-Technical AbstractSmall, elongated organic molecules are the archetypal materials behind today's $100 billion/yr liquid crystal display industry. When the shape of these molecules is made less symmetrical - e.g., by introducing a kink in their central core or a branching of an otherwise linear structure - they often spontaneously form nanometer size domains that are more ordered than the overall, macroscopic material, which still exhibits an essentially fluid-like behavior. This interesting dichotomy across length scales can be exploited to produce novel, easily processible structured fluids with potential for new technologies much broader than electro-optical displays - technologies ranging from unique soft actuators to personal-scale green power generation. This project will enhance existing, and develop and demonstrate new, experimental and analytical tools and procedures to connect short-range order in low symmetry molecular systems to larger scale properties of potentially significant technological impact. It will also aim to synthesize and characterize a completely new class of reduced-symmetry complex fluids based on combining the exquisite length tunability of DNA duplexes with the bent-shaped molecular structures that have revitalized research in the liquid crystal field in recent years. Undergraduate and graduate students will be mentored through a rare 'trifecta' of cross-disciplinary exposure (physics, chemical physics, and chemistry), regular opportunities for participation in international research collaboration, and a balance of cutting-edge small and large (national) scale laboratory experience. Technical AbstractThis project, supported by the Condensed Matter Physics (CMP) and Solid State and Materials Chemistry (SSMC) Programs will pursue materials' synthesis and experimental studies of orientationally-ordered fluids composed of complex-shaped molecular constituents, ranging from reduced-symmetry liquid crystal monomers and dimers to lyotropic solutions in which tunable-length DNA duplexes are combined with a bent-shaped aromatic core structure in a novel approach to produce a reduced-symmetry nematic fluid. The project will test the generality of the concept that reducing the symmetry of particles significantly enhances the nature and degree of nanoscale ordering among them (effecting, e.g., a biaxial, polar, or chiral nanostructure), while the overall system maintains higher (fluid-like) symmetry at the macroscopic scale. The response of these materials to external fields (electro-optical and electro-mechanical responses in particular) will be assessed for potential technological applications. The investigation will employ a variety of techniques aimed at: i) detailing the nanostructure, using synchrotron X-ray facilities (including NSLS-II) and direct imaging via cryo-TEM methods, and ii) connecting short-range structure to macroscopic properties, utilizing sensitive optical probes and external electric and magnetic fields. Undergraduate and graduate students will be mentored through a combination of cross-disciplinary exposure (physics, chemical physics, and chemistry), a balance of cutting-edge small and large (national) scale laboratory experience, and regular opportunities for participation in international research collaboration.