Abstract
The smectic phase with an anomalous dependence of the tilt angle on temperature for a bent-core liquid crystal is observed for the first time. In this phase, the tilt angle decreases on cooling and in the temperature range below the tilted phases, re-entrant orthogonal smectic phase (SmAPA) appears. At higher temperatures, a ferroelectric phase with a helix of short pitch is formed. As the tilt angle decreases on cooling, the helical phase transforms to a surface-stabilized (helixfree) flat anti-ferroelectric structure. This transition is explained by the out-of-plane biaxial anchoring energy
Highlights
Liquid crystals (LCs) belong to a unique state of soft matter where myriad liquid crystalline phases are exhibited
The physical properties and the phase transitions of a smectic liquid crystal material built from achiral bent-core molecules are investigated by electro-optics, polarizing microscopy, birefringence, and spontaneous polarization
We find that there is an additional, previously not recognized, low-temperature phase SmAPA which is a nontilted smectic phase occurring in an inverted phase sequence below the tilted one
Summary
Liquid crystals (LCs) belong to a unique state of soft matter where myriad liquid crystalline phases are exhibited. An emergence of these phases depends on the molecular shape, chirality, and temperature. The most successful LC used in the liquid crystal display (LCD) industry is still the nematic phase of rodlike (or calamitic) molecules. Calamitic LCs may exhibit a number of smectic phases, such as orthogonal (SmA), tilted (SmC) phases, and their variants. The tilted, SmC-like smectics built from chiral molecules exhibit spontaneous polarization [1] and may form ferroelectric SmC∗ and antiferroelectric SmC∗A phases. A number of intermediate ferrielectric subphases may emerge in the temperature range in between SmC∗A and SmC∗ [2,3]. At the time of the discovery of ferroelectric liquid crystals (FLCs), the molecular chirality was considered to be the essential condition for ferroelectricity
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