Dielectric pre-transitional behavior in the vicinity of isotropic–blue phase III transition

Abstract

Pre-transitional effects have been observed from the study of static dielectric permittivity () and its temperature derivatives () near the isotropic to blue phase-III (I–BPIII) transition in a highly polar T-shaped liquid crystalline material having a stable BPIII phase which persists over a comparatively wide range of temperature (∼8°C). The pre-transitional behavior near I–BPIII transition is found to be very similar to that observed in isotropic–nematic (I–N) transition. Landau–de Genes and Maier–Saupe approaches, used earlier to describe anomalous behavior of ε_S near the I–N transition, have been implemented to investigate the present pre-transitional behavior near the I–BPIII transition. The value of critical exponent (α) for the I–BPIII transition is found to be close to that of the reported I–N transition. Temperature-dependent behavior of and have also been interpreted in terms of field-induced increments of basic thermodynamic quantities, namely internal energy, entropy, and Helmholtz free energy.

Keywords:

• liquid crystal
• phase transition
• dielectric spectroscopy
• pre-transitional effect

Acknowledgments

The authors are grateful to the CSIR, Government of India, for partial financial grant. One of the authors (BKC) is grateful to the AvH Foundation for providing the HP4192A impedance analyser.