Structure and Dynamics in Temperature-Sensitive and Anistropic Complex Fluids

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**** NON-TECHNICAL ABSTRACT ***This experimental program will explore the fundamental properties of complex fluids such as colloidal suspensions, emulsions and oil-water interfaces, polymer and surfactant solutions, liquid crystals, and mixtures thereof. These soft materials find applications in the paint, food science, and cosmetics industries, in the practical control of fluid rheologies and microfluidics, in cell biology, in high-tech problems such as photonics, lithography, biochemical sensors and processors, and in design of advanced composites. This project will create new materials and will elucidate a variety of basic phenomena such as melting, diffusion, and self-assembly. Knowledge gained in these studies will impact on our ability to manipulate particles (micro- and nano-particles) and macromolecules in solution, and thereby offer insight for the practical problems listed above. Technology developed as part of this research has potential economic benefit, e.g. it has led already to the formation of a start-up nanotechnology company. The program will also educate a new generation of scientists and engineers about soft materials; these students will add to the technological infrastructure of the nation. **** TECHNICAL ABSTRACT ****This individual investigator award supports experiments in soft materials to elucidate traditional phenomena such as melting, diffusion and self-assembly using non-traditional materials and observational tools. The research will also create and understand the behavior of a variety of novel 'hyper-complex fluids', i.e. complex fluids composed of more than one soft material. The project involves three sets of experiments; 1) Temperature-sensitive polymers will be employed to induce novel phase behavior, and to enable in-situ observations of phase transition dynamics and scaling in a range of complex fluids. The focus of this study will be on melting, freezing, solid-solid phase transitions, and jamming of temperature-sensitive lyotropic colloids. 2) Diffusion and structure of isotropic and anisotropic mesogens (e.g. spherical and ellipsoidal particles) in unusual background solvents such as nematic liquids and two-dimensional interfaces will be investigated. 3) New complex fluid materials and phenomenology created by mixing single-wall carbon nanotubes (SWNTs) in various soft materials will be studied. Preliminary studies have identified a plethora of complex fluids (e.g. surfactant solutions, gels, epoxies) whose properties (e.g. rheological, electrical) are dramatically changed by addition of SWNTs. Investigation of this system class will be from a fundamental viewpoint. In addition new methodologies for manipulation of nanotubes will be identified. The students involved in these research projects will learn skills that will add to the technological infrastructure of the nation.