Synchrotron X-ray investigation of the layer spacing in a series of low molar mass bi-mesogen organosiloxane smectic materials

Abstract

The temperature dependence of the layer spacing of a series of chiral bi-mesogen organosiloxane liquid-crystal materials is presented. The detailed measurements were taken at the ELETTRA radiation source in Trieste on thin specimens contained between glass coverslips. In the materials with 10 and 11 spacers between the siloxane and the mesogenic moiety, it is observed that the temperature dependence of the layer spacing is not monotonous. In the material with six spacers, there is an abrupt change of 0.01 nm in the layer spacing between 35 °C and 36 °C. In this temperature range, domains with both layer spacing coexist. This observation is in agreement with polarised light microscopy observations; however, detailed differential scanning calorimetry (DSC) measurements show no heat associated with this transition.

Keywords:

• organosiloxane
• bi-mesogen, synchrotron X-ray
• smectic liquid crystal
• ferroelectric
• layer spacing

Acknowledgements

The authors would like to thank Prof. Peter Zugenmaier for providing the liquid-crystal specimens used in this work.