Effect of alkyl chain length in the terminal ester group on mesomorphic properties of new chiral lactic acid derivatives

ABSTRACT

Two series of new liquid crystalline lactic acid derivatives with a terminal ester group have been synthesised. The effect of this ester unit and the length of its alkyl chain on the mesomorphic and dielectric properties of the compounds exhibiting a broad temperature range of chiral smectic phases have been studied. We found that the mesomorphic behaviour and phase transition temperatures are strongly affected by the molecular architecture. Depending on the alkyl chain length in the terminal ester unit, the studied materials exhibited paraelectric smectic A*, ferroelectric tilted smectic C* and antiferroelectric smectic C_A* phases over a broad temperature range. The physical properties of the compounds have been studied by optical polarising microscopy, differential scanning calorimetry, electro-optic measurements, small-angle X-ray scattering and dielectric spectroscopy. Furthermore, the homologues with short terminal alkyl chains showed a very small layer shrinkage at the transition from the orthogonal SmA* to the tilted SmC* phase, which is a characteristic feature of ‘de Vries-type’ behaviour.

Graphical Abstract

KEYWORDS:

• Chiral liquid crystal
• lactic acid derivative
• terminal ester group
• mesomorphic properties
• dielectric spectroscopy
• layer shrinkage

Acknowledgements

This work was supported by research projects of Czech Science Foundation (13-07397P) and MEYS (LD14007). The authors are very grateful to Prof. F. Giesselmann for the access to the small angle X-ray scattering equipment and for discussions. The authors greatly appreciate the access to computational resources provided by the MetaCentrum under the program LM2010005 and the CERIT-SC under the program Centre CERIT Scientific Cloud, part of the Operational Program Research and Development for Innovations (Reg. no. CZ.1.05/3.2.00/08.0144).

Supplementary material

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Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by research projects of Czech Science Foundation: [Grant number 13-07397P] and MEYS: [Grant number LD14007].