Dielectric Relaxation Modes in the Phases of Antiferroelectric Liquid Crystals

Abstract

Complex dielectric constant of an antiferroelectric liquid crystal family represented by 4-(1-methylheptyloxycarbonyl) 3-fluorophenyl 4'-dodecylbiphenyl-4-carboxylate was measured in the frequency range between 10-2 Hz and 107 Hz. The experimental results were analyzed using a generalized Cole-Cole expression, and seven dielectric relaxation modes were confirmed to exist. Possible models of collective molecular motions are proposed for mode assignments on the basis of the experimental results of temperature dependence of the modes, together with those of cell gap and bias field dependences.

Characteristic dielectric parameters of para-, ferro- and antiferro-electric phases of (S)-4-(1-methylheptyloxycarbonyl)phenyl-4′-(6-pentanoyloxyhex-1-oxy)biphenyl-4-carboxylate

“…9) are 107 and 42 kJ/mol, respectively. These two relaxation modes in the SmC A * phase have been observed in other materials also [22][23][24][25][26][27].…”

“…The origins of the two modes in the SmC A * phase are discussed in detail by different groups and various explanations have been proposed [22][23][24][25][26][27]. Buivydas et al [23] have assigned these two modes to the in-phase and anti-phase azimuthal angle fluctuation of the directors in the anti-tilted molecular pairs.…”

Investigation of relaxation processes in anticlinic smectic C* (Sm) phase of Liquid Crystals by dielectric spectroscopy

“…has, another collective mode due to phase fluctuations (Goldstone mode) [9][10][11] phase contains two characteristic relaxation modes observed in kHz and MHz regions, respectively [12][13][14][15][16][17][18][19][20]. Here it would be worthwhile to mention that, although the temperature-dependent dielectric behaviour in the antiferroelectric phase have been investigated in different types of antiferroelectric liquid crystal (AFLC) materials, yet a unique interpretation or assignment of different relaxation modes has not been possible [12][13][14][15][16][17]. Bias field studies of these two modes of SmC n A phase are scarce.…”

Electro-optical properties of an orthoconic liquid crystal mixture (W-182) and its molecular dynamics

“…Modes IA and II are referred to as P H and P L modes, respectively. [25][26][27][28][29][30] Mode II ͑P H mode͒ can be observed from room temperature to 98°C and mode IA ͑P L mode͒ can be observed from 50 to 91°C.…”