The investigation of the relaxation processes in antiferroelectric liquid crystals by broad band dielectric and electro-optic spectroscopy

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].…”

Field induced modification of SmC∗–SmCA∗ transition temperature of a fluorinated antiferroelectric liquid crystal

“…(2) with De = 1.28 and 1.84, and relaxation frequencies 2.7 MHz and 49 kHz, respectively, for the P H and P L relaxation process. It should be noted that the parameters are little higher than those obtained generally in AFLC materials [17,19,21] which can be recognized as the typical sample characteristic. The other parameter b k is found to be always less than 0.1, except near the fluctuating transition region.…”

“…Fig. 2 shows the frequency dependence of the real (e 0 ) and imaginary (e 00 ) parts of dielectric permittivity e * (x, T) in the antiferroelectric SmC A * phase at T = 405 K. The spectrum reveals two well-separated low frequency (P L ) and high frequency (P H ) relaxation processes which have been observed only in the SmC A * phase of the investigated compound and in some other AFLC materials [14][15][16][17][18][19][20][21][22].…”

“…Above this critical field, the strength P L decreases abruptly and P H is suppressed. Panarin et al [21] reported that the relaxation frequency of the P L mode decreases at low bias field and corresponding strength increases. In the case of MHPOBC, strength and frequency of both modes have been found to be approximately invariant upto 20 kV cm À1 [19].…”

“…The mode was called antiferroelectric Goldstone mode by Hiraoka et al [26] and antiphase azimuthal angle fluctuation by Buivydas et al [17]. (iv) Disturbance of antiferroelectric helix due to coupling between dielectric anisotropy and electric field De E 2 by Panarin et al [21]. However, this process cannot be detected during dielectric measurements.…”