New compounds with a TGBA-TGBC-SmC* phase sequence

Abstract

A new series of lactic acid derivatives has been prepared with molecular cores consisting of two laterally substituted biphenyls connected by an ester group. The compounds exhibited the TGBA phase in a broad temperature range. In addition, for some compounds, a narrow blue phase was found above the TGBA phase on cooling from the isotropic phase. Except for the compound with the shortest chain, the TGBC phase appeared below the TGBA phase. The low temperature SmC* phase existed within the interval up to 80 K, including the overcooled state, which was down to room temperature. In the compounds studied a strong pre-transitional phenomenon took place manifested as a broad peak on the differential scanning calorimetry plot in the isotropic phase. The phases were established on the basis of a planar sample and free-standing film microscope observation. Small angle X-ray diffraction measurements provided information about layer spacing, d, and confirmed the phase assignment. Dielectric spectroscopy revealed the soft and Goldstone modes in the respective TGBA and SmC* phases.

Keywords:

• ferroelectric liquid crystals
• TGBA phase
• TGBC phase
• dielectric spectroscopy
• lactic acid derivatives

Acknowledgements

This work was supported by projects IAA100100710 and IAA100100911 (Grant Agency of AS CR), by Research Project AVOZ 10100520 and Grant No. 202/09/0047 from the Grant Agency of the Czech Republic. The X-ray diffraction measurements were performed at the Structural Research Laboratory, Chemistry Department, University of Warsaw, Poland, which was established with financial support from the European Regional Development Fund, Project No: WKP 1/1.4.3./1/2004/72/72/165/2005/U.