We explore new types of complex dispersions that have unique structures at many length scales. For over a decade, we have been emulsifying liquid crystals and studying how the temperature-dependent anisotropic elastic properties of liquid crystal phases can affect the shape of droplets. This top-down process has led to the creation of an aqueous dispersion of flat coin-like birefringent microdisks. In addition, we are interested in the structure, rheology, and optical properties of many kinds of complex dispersions such as mixtures of surfactants, polymers, clays, emulsion droplets, liquid crystals, and ferrofluids.





This image shows shape-selective aggregation of microdisks into columns using an entropic depletion attraction. The aggregation is induced by adding additional sodium dodecyl sufate (SDS) micelles. The osmotic pressure of these micelles causes disks to aggregate face-to-face, whereas spheres (outside the column) do not aggregate. The shape selectivity of the aggregation arises from very different excluded volumes for the micelles for disks that nearly touch as compared to spheres that nearly touch. This shape selectivity can be used to purify disks from spheres in a mixed dispersion. See: "Osmotically Driven Shape Dependent Colloidal Separations", T.G. Mason, Phys. Rev. E Rapid Comm. 66, 060402 (2002).



This image shows a microscopic liquid crystal droplet illuminated by white light using crossed polarizers. Studying the structure, interactions, and rheology of microscale and nanoscale dispersions of particles such as these will lead to new advances in the science of complex fluids.


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