Synthesis and mesomorphic properties of new compounds exhibiting TGBA and TGBC liquid crystalline phases

Abstract

We synthesised a series of rod‐like mesogens with a (S)‐2‐methylbutyl‐(S)‐lactate unit in the chiral chain that exhibited extremely wide temperature ranges in the TGBA and TGBC* phases. TGB phases were identified, based on typical textures in confined samples and in free‐standing films, by Grandjean‐Cano texture and by NMR studies on a deuterium‐labelled isotopomer. A sufficiently high electric or magnetic field transformed the TGBA and TGBC* phases into their respective SmA and SmC* phases, the TGB structures being restored within some 20–30 minutes. Therefore values of the spontaneous polarisation and spontaneous tilt angle, when measured under a sufficiently high field, gave evidence of the properties of the SmC* phase. Temperature dependencies of relaxation frequency, dielectric strength, selective reflection and layer spacing showed anomalies at a certain temperature within the TGBC* phase range. Also, changes in textures, as well as in ²H‐NMR spectra, occurred at this same temperature. These results suggest the existence of two TGBC* phases.

Keywords:

• lactate unit
• the TGBA phase
• the TGBC* phase
• dielectric properties

Acknowledgements

This work was supported by Project No. 202/05/0431 from the Czech Science Foundation and No. IAA100100710 from Grant Agency of the Academy of Sciences of the Czech Republic, Project ESF COST D35 WG13‐05, Czech–Polish bilateral collaboration program No. 8 (2006–2007) and OC 175 program under the Ministry of Education, Youth and Sports of the Czech Republic. V. D. thanks the Italian PRIN2005 project and Professor C. A. Veracini for helpful discussions.