NMR spectra of chiral smectic liquid crystals differing in helical parameters

ABSTRACT

Chiral liquid crystals with three-ring rigid core were examined. The method based on the selectively reflected light was used to determine the helical pitch. The helical twist sense was worked out using the polarimetry method. ¹H and ¹³C NMR measurements were performed. The influence of three molecular structure parameters: the type of chiral centre, the length of non-chiral chain and substitution of benzene ring by fluorine atoms, on helical pitch, handedness of helical structure and values of chemical shift in proton and carbon spectra was determined. The change of the length of non-chiral terminal chain has the most significant influence on the temperature dependence of helical pitch. All tested parameters have the biggest influence on the values of chemical shift of atoms in the chiral centre.

Graphical Abstract

KEYWORDS:

• Liquid crystals
• SmC_A* phase
• helical pitch
• helical twist sense
• NMR spectra

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here

Additional information

Funding

This work was supported by the Wojskowa Akademia Techniczna [PBS 23-651, RMN 08-687].