Gelation of Liquid Crystals with Self-Assembled Fibers

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Abstract
Physical gelation of liquid crystals with low molecular weight gelators leads to the formation of a new class of anisotropic gels that have great potentials for optical, electrical, and photofunctional materials. The liquid crystalline (LC) physical gels are microphase-separated anisotropic composites consisting of liquid crystals and self-assembled solid fibers. For these materials, the isotropic–anisotropic transitions due to liquid crystals and the sol–gel transitions due to gelators occur reversibly and independently. The thermal, optical, and electrical properties of the LC gels are tuned by the selection and combination of the components, which determine the microphase-separated structures. LC gels based on room temperature nematic liquid crystals show electro-optical switching on twisted nematic and light scattering modes. The electro-optical properties can be improved in the presence of fiber additives. Discotic liquid crystals that function as hole transport materials have been used as LC components of anisotropic gels. The discotic gels exhibit hole mobilities higher than those of the liquid crystal alone. Chemical modification of gelators with functional moieties is another versatile approach for functionalization of LC gels. Hydrogen-bonded gelators with photoswitchable azobenzene moieties have been developed and complexed with liquid crystals. The resultant photoresponsive LC gels show light-induced structural changes, which are applicable to rewritable information recording.