Frustrated structure of an anticlinic-like smectic-C phase

Area of Science:

• Materials Science
• Condensed Matter Physics
• Crystallography

Background:

• Liquid crystals exhibit diverse mesophases with unique molecular arrangements.
• The anticlinic-like tilted mesophase in octylphenyl-2-chloro-4-(p-cyano-benzoyloxy) (DB8Cl) has been proposed as a bilayer smectic structure.

Purpose of the Study:

• To investigate the low-temperature anticlinic-like tilted mesophase of DB8Cl using polarising optical microscopy.
• To analyze the observed optical textures and their relation to the molecular structure and optical properties.

Main Methods:

• Polarising optical microscopy was employed to study the mesophase.
• Experimental results were analyzed using a model considering the distribution of the principal optical axis.

Main Results:

• Observed double stripe patterns in planar oriented samples, indicative of double periodic refractive index modulation.
• A temperature-dependent long-period modulation and a cell thickness-independent short-period modulation were identified.
• The proposed molecular structure of DB8Cl involves dimers, resembling bent-core molecules but with greater complexity.

Conclusions:

• The observed optical properties suggest a complex molecular arrangement in the DB8Cl mesophase.
• The original proposed structure does not fully explain the periodic variation of the principal optical axis.
• DB8Cl exhibits a unique dimeric structure with similarities to banana-like liquid crystals.