Current Topics in Smectic Liquid Crystal Research

Abstract

Interest in the smectic liquid-crystalline state of matter received a substantial boost with the discovery by Meyer in the mid-1970s that a chiral smectic C (SmC*) phase exhibits a spontaneous electric polarization, and with the subsequent demonstration by Clark and Lagerwall of the surface-stabilized SmC* ferroelectric liquid crystal at the beginning of the 1980s. Since then, chiral smectic phases and their plethora of polar effects have dominated the research in this field, which today has reached a mature state where the first commercial microdisplay applications are now shipping in millions-per-year quantities. In this Review we discuss some of the topics of highest interest in current smectic liquid crystal research, and address application-relevant research (de Vries-type tilting transitions without defect generation and high-tilt antiferroelectric liquid crystals with perfect dark state) as well as more curiosity-driven research (the nature and origin of the chiral smectic C subphases and their intermediate frustrated states between ferro- and antiferroelectricity).

Integration of electro-active π-conjugated units in nanosegregated liquid-crystalline phases

“…30 In de Vries type ferroelectric liquid crystals, a temperature-independent layer spacing of the ferroelectric LC phase has been reported. 31 Only one example of columnar liquid crystals of triphenylene derivatives bearing six oligosiloxane chains has been reported. 32 For side chain polymers, high hole mobility was observed in a nanosegregated smectic phase in which rigid side chain mesogenic terthiophene units and liquid-like polysiloxane chains were microscopically separated.…”

Carbon Nanotubes in Liquid Crystals

“…We investigated the effects of 75 SWCNT doping on the mesomorphism of an antiferroelectric liquid crystal mixture exhibiting a particularly rich polysmectic phase sequence 42 , including the still mysterious intermediate chiral smectic-C phases 53 . Although the CNT concentration in the LC was as small as 0.002 wt.-%, their 80 presence had a profound effect on the phase sequence, all chiral smectic-C-type phases except the ordinary SmC* being suppressed.…”

1H Nuclear Magnetic Resonance of a Ferroelectric Liquid Crystalline System

“…In order to understand the phase transitions and molecular orientational order in liquid crystals, various types of study, including nuclear magnetic resonance (NMR) and electrical field effect, have been conducted. Thermotropic liquid crystals can have nematic, smectic and cholesteric phases at different temperatures [1][2][3][4]. In contrast to the nematic phase that possesses orientational order without any positional order, the smectic phase possesses both minimal and orientational orders.…”

“…While the electric permittivity obeys CurieWeiss law in this phase, the origin of its ferroelectricity is the molecular chiral asymmetry [1,7]. There is no spontaneous polarization in Sm-A, but an electroclinic effect is shown under electric field [8].…”

“…Since molecular arrangement and the reflective index can easily be changed by applying either an electric field or a magnetic field, nematic liquid crystals are used as electro-optical devices such as displays and monitors [1,9]. The ferroelectric liquid crystals show very fast operating time with low dielectric constants [1].…”