Dielectric and optical properties of heterogeneous microcomposite materials based on porous matrices and liquid crystals

Porous matrices with determined structure, pore shape, size, and volume fraction, impregnated with liquid crystals (LC) can be used as model systems to understand physical properties of dispersed LC - materials important for display applications. Using dielectric spectroscopy, static and dynamic light scattering we have investigated equilibrium and dynamic properties of LC dispersed in porous matrices with randomly oriented, interconnected pores as well as in parallel cylindrical pores with different pore sizes. The spatial confinement and the existence of a highly developed interface in porous matrices have the strong influence on dielectric and optical properties of LC which resulted in the appearance of a low frequency relaxational process (f less than or equal to 10 KHz) absent in bulk and a strong modification of modes due to the molecular rotation around short axis and librational motion. All observed relaxational processes in confined LC are not frozen even at temperatures about 20 degrees below the bulk crystallization temperature. One of the new properties among others observed for nematic LC confined to porous matrices is the appearance of slow relaxational process which does not exist in the bulk LC and wide spectrum of relaxation times (10(-8) - 10)s.