Collective and molecular modes in ferroelectric and antiferroelectric liquid crystals

A new 4-(1-methylheptyloxycarbonyl)phenyl4´-octyloxybiphenyl-4-carboxylate (MHPOBC) analog exhibiting ferroelectric and antiferroelectric properties has been studied by dielectric and electro-optic methods. Dielectric measurements were performed using a gold coated cell, thickness 23 /spl mu/m. In the ferroelectric SmC* phase a pronounced Goldstone mode was found, whereas in the antiferroelectric SmC*/sub A/ phase two dielectric relaxation processes have been observed. It has been shown that collective processes, like soft mode and Goldstone mode, show non-Arrhenius behavior. The measurements of spontaneous polarization were performed by means of the reversal current method using a cell of thickness 7 /spl mu/m coated with indium-tin oxide (ITO) layers. Temperature dependencies of spontaneous polarization are discussed in terms of the mean-field model.