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Anisotropic Solvation of Rod-Shaped Nanostructures in Liquid Crystalline Solvents
Our interest
in liquid crystals is centered around the understanding of how nanostructured solutes such as rod-shaped polymers
align in an anisotropic medium. We are studying the orientation and degree of alignment
of conductive light emitting polymers in thermotropic liquid crystals by using single molecule polarization
spectroscopy. Because of the larger size of a polymer solute compared to the liquid crystalline molecules,
the solute is aligned to a much greater extent. The aim of this project is to gain a deeper understanding of how molecular solvent-solute interactions govern
short and long range orientation, alignment and diffusion of solutes in liquid crystalline solvents. We are
examining the anisotropic solvation and diffusion of macro-molecules and nanoparticles as a function of size, shape, liquid
crystalline phase, and solvent order. By using a combination of ensemble and single molecule/particle polarization
spectroscopy techniques we are able to extract solute order parameters, which give us detailed information about anisotropic
solvation in liquid crystals.
The figure above shows a typical fluorescence transient (left) of polymer molecules diffusing in a liquid crystal. Each burst corresponds to a single molecule passing through the laser excitation spot. The fluorescence is split into two orthogonally polarized components (blue and red trace), which allows us to calculate the polarization anisotropy of each molecule and then generate a histogram of polarization anisotropy values (right). Modeling of the polarization anisotropy distribution allows us to extract the degree of orientational alignment of the solute in the liquid crystal. Publications:
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