Influence of Temperature on Surface Tension of Liquid Crystals in the Cyanobiphenyl and Cyano-oxybiphenyl Series

ABSTRACT

The surface tension of low molar mass liquid crystals from the nCB and nOCB series was evaluated for temperatures, T, corresponding to the different phases of the materials, using the pendant drop method. With the exception of the materials which presented a smectic phase, and far from the transition temperatures the surface tension was shown to decrease with increasing temperature. The atypical behaviors (discontinuities of surface tension, γ, and of ∂γ/∂T, upward jump, and increase of surface tension with increasing temperature) that were observed for temperatures in the proximity of the transition temperatures and for the materials that presented a smectic phase, was explained in light of the ordering of the molecules.

Keywords:

• OCB and CB liquid crystals
• pendant drop method
• surface tension

Acknowledgments

The authors would like to thank FAPESP for financial support and are also grateful to Centro de Technologia e Invação da Braskem for analyses of Pressure Volume and Temperature of materials.