Layer modulated smectic-C phase in liquid crystals with a terminal hydroxyl group

Area of Science:

• Materials Science
• Condensed Matter Physics
• Crystallography

Background:

• Liquid crystals exhibit diverse mesophases, including various smectic-C phases.
• Understanding the local layer structures is key to predicting material properties.
• Terminal functional groups, like hydroxyl, significantly influence liquid crystal phase behavior.

Purpose of the Study:

• To elucidate the local layer structures of three distinct smectic-C phases (SmC, SmC', and SmC″) in a liquid crystal.
• To determine the role of intermolecular hydrogen bonding in the formation of these phases.

Main Methods:

• High-resolution X-ray diffraction
• Microbeam X-ray diffraction
• Fourier Transform Infrared Spectroscopy (FTIR)

Main Results:

• SmC phase identified as the conventional SmC1 phase.
• SmC″ phase characterized as a bilayer SmC2 phase.
• SmC' phase exhibits an in-plane modulation structure, identified as a smectic-C antiphase.
• FTIR suggests intermolecular hydrogen bonding is essential for inducing SmC' and SmC″ phases.

Conclusions:

• The study clarifies the structural characteristics of three smectic-C phases.
• Intermolecular hydrogen bonding plays a critical role in the formation of specific smectic-C phases, including antiphase and bilayer structures.
• This research contributes to the fundamental understanding of liquid crystal phase transitions and structures.