Dielectric Spectroscopy of the Electroclinic Effect in the Ferroelectric Liquid Crystal Materials

ABSTRACT We present the dielectric properties of two pure ferroelectric liquid crystal materials (C11 and C12) exhibiting cholesteric (N*), paraelectric smectic A (SmA*), and ferroelectric chiral smectic C (SmC*) phases. In the dielectric measurements carried out without a DC bias field, we studied the soft-mode relaxation in the SmA* phase. From experimental data and using the results of a Landau model, we evaluate the electroclinic coefficient in the SmA* phase. A soft-mode-like mechanism was also observed in the N* phase for a compound with a shorter chain (C11). This relaxation process is not detected for the homolog with a longer chain (C12). The observation of this mechanism is linked to smectic order fluctuations within the N* phase whose amplitude is more enhanced close to the SmC*−SmA*−N* multicritical point.