The molecular aspect of the double absorption peak in the dielectric spectrum of the antiferroelectric liquid crystal phase

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.…”

“…Several groups have proposed the existence of both relaxations in antiferroelectric phase; although they individually explain that such two modes are based on different originations, no definite unique origin of such modes exist. 25- 30 Buivydas et al finally proposed the origin of P L and P H modes as arising due to a collective reorientation of the molecules around the cones in the same direction, i.e., in phase motion in variable ͑azimuthal angle͒ in antitilt pairs, and P H mode arises due to the collective reorientation of the molecules around the cones in the opposite direction and antiphase motion in azimuthal angle in their antitilt position. The Buivydas model for the explanation of P L and P H modes until now has been satisfactorily accepted and it is satisfactory enough to explain the origination of the existence of such relaxation in antiferroelectric phase.…”

The investigation of the relaxation processes in antiferroelectric liquid crystals by electro-optic spectroscopy

“…7 Nevertheless, the problem of finding the mechanisms governing the various relaxation processes in the antiferroelectric phase has not yet been solved and the aim of this letter is to unambiguously establish these mechanisms using electrooptic spectroscopy of a AFLC. Though the nature of the relaxation process in SmC A phase has somewhat been speculated in earlier experimental publications [3][4][5] and theoretical works, 8,9 nevertheless no clear evidence is given and theoretical investigations are divorced from the experiments. In this letter, the mechanism of the collective processes is found on comparing the results of the dielectric and electro-optic spectroscopy with those from the theoretical investigations.…”

“…[3][4][5][6] The dielectric spectra in the frequency range from 10 Hz to 1 GHz show the existence of two collective relaxation processes and two molecular relaxation processes in the SmC A phase and these are denoted as Processes 0,1,2,3 with increasing of the relaxation frequency. 6 The lower frequency processes ͑Process 0 and Process 1͒ are found to exist 6 only in the two antiferroelectric phases SmC A and AF phases.…”

“…A determination of the origin of the collective modes will allow for a further improvement in these materials to occur with regard to their switching speeds and hence increase their usefulness for displays and electro-optic devices. A study of the relaxation processes has been made using dielectric spectroscopy, [3][4][5][6] electro-optics, 4 and photon correlation spectroscopy. 7 Nevertheless, the problem of finding the mechanisms governing the various relaxation processes in the antiferroelectric phase has not yet been solved and the aim of this letter is to unambiguously establish these mechanisms using electrooptic spectroscopy of a AFLC.…”