The temperature and frequency dependent dielectric relaxation behavior of a liquid crystalline (S)-(+)-1-methylheptyl 4-[2-(4-alkoxyphenyl) thiophene-5-carbonylthiooxy] benzoate system is reported. Interesting successive antiferroelectric-ferroelectric-antiferroelectric (AF-FE-AF) phase transitions are observed in this system resembling the successive phase transitions observed in crystalline Rochelle salt. The smectic-C*(SmC*) to AF1 phase transition (around 103.0 °C) is first order in nature, predicted from the use of Orihara and Ishibashi theory. It is also found that a contribution of the ferroelectric SmC* phase ordering penetrates even in the antiferroelectric AF1 (SmCA*) and AF2 (SmCA*) phases very close to the SmC*-AF1 and SmC*-AF2 phase boundaries (critical regions). It is suggested that this type of mixing of AF and FE phases might cause surface induced ferroelectric- or ferroelectric-type ordering near the AF-FE phase transitions. A soft mode with Debye-type dispersion was observed in the SmA phase. The thermal behaviors of dielectric dispersion, absorption, and dielectric strength in different phases are also reported and discussed.
Physical Review E
Copyright 2003 American Physical Society. Available on publisher's site at http://dx.doi.org/10.1103/PhysRevE.67.041704.
Kundu, S. K.; Chaudhuri, B. K.; Seed, Alexander; Jakli, Antal (2003). Dielectric Relaxation Behavior of a Liquid Crystal Showing an Unusual Type of Antiferroelectric-Ferroelectric-Antiferroelectric Phase Sequence. Physical Review E 67(4) doi: 10.1103/PhysRevE.67.041704. Retrieved from https://oaks.kent.edu/cpippubs/166