Structure formation in columnar mineral liquid crystals in confinement (D06)

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Following up on our research, we want to study effects of confinement on liquid-crystal phases of anisometric colloids. Since this also requires the use of optical techniques, we shift our emphasis from boardlike Goethite to platelike Gibbsite particles. These hexagons can be prepared with optically accessible diameters using seeded growth and in principle can be made fluorescent. We have previously found that the native platelets form a nematic phase and 2 types of columnar phases: both a hexagonal phase with long-range 2D ordering and a hexaticlike phase which is ordered orientationally but lacks true long-range positional order. Since this is intrinsically related to the possibility of fluctuations of the columns and the occurrence of defects, one of our research goals is to study how the hexagonal and hexatic order is affected by confinement and anchoring in different geometries (gaps, wedges). We also intend to use patterned surfaces to study the packing of columns in wedges. An important technique to study these confined systems is microradian x-ray diffraction, but also newly developed synchrotron techniques like x-ray microscopy could be interesting. These measurements will be complemented by (polarization and/or confocal) light microscopy to address the local (defect) structure.