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(a) Molecular structure of the benzoperylene derivative. This compound exhibits a hexagonal columnar phase from to ambient temperature. (b) Schematic representation of the homeotropic (face-on) and planar (edge-on) orientations of a columnar mesophase.
Dependence with the film thickness of the colLC orientation and wetting behavior observed after thermal annealing by DIC microscopy. The scale bar indicates in (a) and in (b) and (c), respectively. (a) For film thicknesses above , the uniform homeotropic orientation of the columnar mesophase extends over several . A small highly birefringent planar region is shown for contrast. Inset: the same image between crossed polarizers. (b) By decreasing the layer thickness down to , the sample exhibits large homeotropic regions in coexistence with a few planar domains. Small circular dewetted zones also appear around defects on ITO surface. (c) A complete dewetting is found for colLC films thinner than . Inset: the same image after a fast Fourier transform.
X-ray diffraction pattern of a single colLC domain observed in the geometry of an open supported film. The sixfold symmetry is the signature of homeotropic alignment of the hexagonal columnar mesophase, investigated in transmission with the x-ray beam normal to the plane of the substrate. The white scale bar indicates .
ITO substrate studied by AFM. (a-1) The region of interest has a square side of and the white bright spots are surface defects of about high, as shown by the corresponding profile in (a-2). (b-1) Zoom in of square side showing the average roughness of the ITO surface of about (b-2).
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