High-resolution calorimetric study of critical behaviour at the smectic-C^*–smectic- phase transition

Abstract

Precise heat-capacity measurements have been made around the smectic-–smectic- phase transition in the R–S mixture of liquid crystal MHPOBC ([1,1′-biphenyl]-4-carboxylic acid, 4′-(octyloxy)-, 4-[[(1-methylheptyl)oxy]carbonyl]phenyl ester) which exhibits ferro- and antiferroelectric phases. Ultra-low frequency ac calorimeter and high-sensitivity differential scanning calorimeter have been used. The measurements revealed the existence of quite slow relaxation near the transition. The heat-capacity anomaly accompanying the transition showed a significant increase as decreasing heat frequency in the ac method. The excess heat capacity observed for a mixture that is closest to the critical point has been analysed quantitatively.

Keywords:

• critical phenomena
• heat capacity
• relaxation frequency
• antiferroelectric liquid crystals

Acknowledgements

This work has been supported in part by the Global Centre of Excellence Programme by MEXT, Japan through the Nanoscience and Quantum Physics Project of the Tokyo Institute of Technology.

Notes

1. 1.The value of X which is thought to be closest to the critical point stated here is slightly different from that mentioned in our previous work [6]. This is mainly because of relatively limited resolution of the experiment there, including the fact that less amount of samples were used in each measurement.