Layer-by-Layer Surface Freezing of Freely Suspended Liquid-Crystal Films

Abstract

Computer-enhanced polarized video microscopy has been used to study the discrete layer-by-layer surface ordering transitions of freely suspended films of 4-($n$-nonyloxy) benzylidene-4-($n$-butyl) aniline (9O.4). Stable tilted hexatic smectic-$I$ surface layers form on both free surfaces of the 2D-liquid smectic-$A$ interior in a monolayer, bilayer, trilayer,...sequence as $T\to T_c$. The appearance of the first ten surface layers is described very well by the simple power-law form, $L=L_0{t}^{-\frac{1}{3}}$, predicted for the surface freezing transition in a system with van der Waals forces.