Orientational order parameter of two cyano nematogens by optical spectroscopy

Abstract

Refractive index and density measurements of two cyano nematogens, namely p-hexyloxybenzylidene p-aminobenzonitrile and p-octyloxybenzylidene p-aminobenzonitrile have been carried out. From these data, orientational order parameter S has been estimated using different methods. Principal polarizabilities have been calculated using the well-known Vuks isotropic and Neugebauer anisotropic models. Polarizability anisotropy has been estimated using Lippincott δ-function, molecular vibration, Haller's extrapolation and Vuks scaling methods. Using these values, the orientational order parameter S has been estimated at different temperatures in their nematic phases. The values obtained have been compared and discussed. Further, using the experimental refractive index data, the nematic crossover temperatures have also been estimated for these compounds.

Keywords:

• Schiff's base compounds
• nematic
• orientational order parameter
• birefringence
• density
• crossover temperature

The authors acknowledge M/s SSD Polymers, Machilipatanam, for providing the facilities for refractive index and density measurements. The authors thank Prof. V.G.K.M. Pisipati and Dr P.V. Datta Prasad for fruitful discussions. The author N. Vinutha is grateful to the University Grants Commission (UGC), New Delhi, for the award of RFSMS fellowship. Dr P. Pardhasaradhi is grateful to the Head of the Department of ECE, K.L. University, Vaddeswram, India, and the management for providing the necessary climate.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Dr D. Revannasiddaiah is thankful to the UGC, New Delhi, for financial support under Major Research Project Scheme (F.No. 41–882/2012 (SR)) and UPE project.