CONVENTIONAL AND NONCONVENTIONAL SPREADING OF A MESOGENIC MATERIAL

Optical microscopic and ellipsometric studies of the spreading of a me sogenic compound on a rough substrate are reported on. The smectic wet s the surface and a precursor film grows whose radius R scales like th e square root of time t: R approximate to (Dt)(1/2). The diffusion coe fficient decreases with temperature and vanishes several degrees below the melting temperature, i.e. the solid phase also ''spreads out'' th rough a precursor film. The effect is analysed in terms of surface-ind uced premelting. This is the first report on such an effect in mesogen ic materials.