DIELECTRIC STUDIES OF THE BIAS FIELD-EFFECT ON THE SOFT MODE OF A FERROELECTRIC LIQUID-CRYSTAL

Using dielectric spectroscopy, surface interactions are detected by th eir influences on the soft mode behavior in the vicinity of the SmC t o SmA phase transition. A non zero pretilt angle is observed in SSFLC cells filled with the ferroelectric liquid crystal -2-chloro-3-methyl butanoyloxy]phenyl}-(4-decyloxy) benzoate. In the absence of a bias el ectric field, the pretilt induces a tilt angle in the SmA phase being coupled to an electric polarization (surface electroclinic effect). T his effect increases with decreasing cell thickness. It depends on the rubbing direction in a specific LC cell and is suppressed by a suffic iently strong bias electric field. Within a bias electric field, the s uppression of the soft mode is described by the ''classical Landau mod el'' whose coefficients are determined from dielectric measurements.