Origin of the Director Tilt in the Lyotropic Smectic C* Analog Phase: Hydration Interactions and Solvent Variations |
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| Authors: | Dr. Johanna R. Bruckner Friederike Knecht Prof. Dr. Frank Giesselmann |
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| Affiliation: | Institute of Physical Chemistry, University of Stuttgart, Stuttgart, Germany |
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| Abstract: | The origin and long‐range correlation of the director tilt in the recently discovered  phase, which is the lyotropic analog of the thermotropic smectic C* (SmC*) liquid crystalline phase, are investigated. Polarized micro‐Raman spectroscopy reveals that the director tilt in the  phase originates from a tilting of the aromatic 2‐phenylpyrimidine cores of the surfactant molecules. Optical measurements of the tilt angle show that its magnitude decreases with increasing solvent concentration, suggesting that the long‐range inter‐lamellar correlation of the tilt directions is reduced at increasing thickness of the solvent layers. The phase diagrams with four different solvents (water, formamide, N‐methylformamide, N,N‐dimethylformamide) are investigated, showing that the  phase is only formed with those solvents that exhibit a dense network of hydrogen bonds. This observation suggests that these hydrogen bond networks play an essential role in the long‐range correlation of the director tilt between adjacent surfactant layers. To verify this assumption, mixtures with deuterated solvents are investigated, showing that the tilt angle in the  phase is indeed reduced by this modification of the solvent′s hydrogen bond network. |
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| Keywords: | amphiphiles hydration interactions liquid crystals Raman spectroscopy solvent effects |
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