[en] In order to better understand which features in dielectric spectra of antiferroelectric liquid crystals (AFLCs) are due to the bulk director geometry and which are due to surface-induced structures, we have performed dielectric spectroscopy measurements with simultaneous texture monitoring on two SmC*-exhibiting AFLC homologues (11- and 12F1M7), at varying cell gap. Such AFLCs are strongly affected by surface action even in fairly thick cells (d≈15µm), with heavy supercooling of the SmC* phase as the most obvious result. We show that the supercooled structure can be removed by AC-field treatment in the SmCa* phase, but some domains may stay in a polar geometry, as reflected in both texture and dielectric signature. On heating from the antiferroelectric SmC?* subphase into SmC*, meta-stable non-helical domains may form at cell gaps much larger than the helical pitch. These domains give rise to a lowfrequency dielectric absorption not seen in bulk SmC* samples.
[Chalmers University of Technology]
