2pi and pi walls in antiferroelectric smectic-C*A and smectic-C free-standing films.

: We observed, in free-standing films of antiferroelectric liquid crystal, dependence of the wall structure on orientation of walls with respect to the external field direction and on parity of number of smectic layer in the film. These observations are explained by anisotropy of two-dimensional elastic constants and by dependence of polarization direction on parity of the film. Investigations in electric and magnetic field allow us to determine the values of elastic constants and longitudinal polarization of the films. Different mechanisms of c -director reorientation were observed when the electric-field direction was reversed or magnetic field orientation was changed with respect to the film plane.