Methylation driven molecular packing difference at the smectic phases of a series of pyridinium-based chiral ionic liquid crystals

Abstract

A series of pyridinium-based chiral ionic liquid crystals were designed and synthesized. All of them exhibit enantiotropic smectic phases. The methylation on the pyridine ring not only decreases the melting point and clearing point, but also drives structural transitions from bilayer molecular packing structures to interdigitated monolayer ones at the smectic A and C phases. Due to entropy increase, the clearing point of the liquid crystal derived from 2-methylpyridine is higher than that derived from 3-methylpyridine, and then that derived from 4-methylpyridine.

Keywords:

• Ionic liquid crystal
• methylation
• chirality
• molecular packing structure

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Natural Science Foundation of the Jiangsu Higher Education Institutions of China [20KJA430009] and the Project of Scientific and Technologic Infrastructure of Suzhou [SZS201905].