Surface-monolayer-induced bulk alignment of liquid crystals: From nematic to smectic-A phase

The Landau-de Gennes theory of surface-induced bulk alignment of nematic li quid crystals is extended to the smectic-il case where both orientational o rdering and positional ordering are present. Assuming strong surface anchor ing, we find that in both nematic and smectic phases, the bulk pretilt angl e is determined by the liquid crystalline order of the first liquid-crystal monolayer at surface through a biaxial surface-bulk transition layer. The smectic layer ordering tends to reduce the spatial variation of the directo r tilt in the transition layer, making the bulk pretilt angle somewhat clos er to the director tilt angle at the surface. Experimental measurement show s results in semiquantitative agreement with theory. [S1063-651X(99)12902-7 ].