Effect of solvent polarity on the self-assembly and dielectric dynamics of non-aqueous lyotropic liquid crystalline phases

Abstract

Binary mixtures comprising cetylpyridinium chloride and non-aqueous solvents of varying polarity [ethylene glycol (ε ~ 37.2) and formamide (ε ~ 109)] were studied via X-ray diffraction, polarisation optical microscopy, differential scanning calorimetry and dielectric spectroscopy. Layered lamellar mesophase was observed in both mixtures. Formamide-based mesophase was found more ordered and stable up to higher temperature (140°C). Ordering and stability of the mesophase was explained considering the higher polarity and dipolar–dipolar interactions of formamide. Dielectric spectroscopy demonstrates the large magnitudes of capacitance and permittivity (Cp ≈ 9 µF and ε ≈ 2428) for mesophase derived from formamide. Dynamical relaxation parameters of both mixtures were discussed and correlated with their structural aspects.

Keywords:

• lyotropic liquid crystalline phase
• cationic surfactants
• non-aqueous solvent
• dielectric spectroscopy
• Cole–Cole relaxation process

Acknowledgement

The authors acknowledge Department of Science and Technology (DST), India, for the financial support.