Antiferroelectric liquid crystals with induced intermediate polar phases and the effects of doping with carbon nanotubes

By mixing a commercial broad-temperature-range nematic liquid crystal mixture with a single-component antiferroelectric chiral smectic exhibiting two different chiral smectic-C-type phases as only mesophases, we have induced three phases which appear in neither of the two components; the paraelectric SmA* phase and the so-called intermediate phases SmC beta* and SmC gamma*, antiferroelectric and heli- electric in nature, respectively. The generation of the two latter phases in mixtures where one component is an essentially non-chiral nematic is highly unexpected, since these phases are generally linked to high degree of smectic order and/or strong chiral interactions. It is probably made possible through microphase segregation driven by the incompatibility of the fluorinated tail of the smectic component with the non-fluorinated constituents of the nematic mixture. We also doped the nematic with single-wall carbon nanotubes (SWCNTs) before adding it to the smectic at the same concentration, allowing us to study the effect of SWCNTs on antiferroelectric liquid crystals. Although the final SWCNT concentration was very small (0.002 wt%) the phase sequence was radically altered, the ordinary SmC* phase now being present all the way between SmA* and crystallization, while all other variations of smectic-C-type order were suppressed. (c) 2007 Elsevier B.V. All rights reserved