For the point of view of electrooptics applications, the sol-gel process  has been adapted [2, 3] for trapping microdroplets of nematogenic organic cornpounds (i.e. liquid crystals, LCs) in a thin-film of a silica-gel based matrix. The LC compounds are dissolved in the starting mixture, loosing their particular properties; further hydrolysis and polycondensation reactions lead to a phase separation that results in the formation of pores which are filled with the organic compound. If adequate processing of the formation of the microdroplets is achieved, the organic compound can gradually recover its nematic LC state. The LC molecules can be oriented in microdomains according to the pore innersurface anchoring that originates from the organic groups on the walls of the pores, e.g. orienting properties induced by -CHH3, -C2H5, -C6H5, etc. Once the phase separation in the Glass Dispersed Liquid.Crystals (GDLC) formation takes place, (LC microdroplets dispersion, figure 1), the LC concentration used in the starting solution becomes simply a figure related to the number and the compactness of microdroplets within the silica-gel matrix. To characterize the orientation and the shape of the microdroplets, the samples were analyzed with a microscope between crossed polarizers, and a radial orientation corresponding to a homeotropic surface condition was obtained in practically all GDLCs, as shown by a characteristic “maltese cross” pattern in the droplets (figure 1).
KeywordsLiquid Crystal Glass Producer Disperse Liquid Transparent Condition Maltese Cross
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