Computational Analysis of Liquid Crystalline Biphenylcyclohexane Derivatives: Estimation of Configurational Entropy, and Phase Stability

Abstract

A comparative computational analysis of two liquid crystalline disubstituted biphenylcyclohexanes (BCHs) of general formula R-C₆H₁₀-C₆H₄-X with R: C₃H₇; X: H (BCH30), and R: C₅H₁₁; X: CN (BCH5CN) has been carried out on the basis of quantum mechanics, statistical mechanics, and intermolecular forces. The atomic net charge and dipole moment at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh–Schrodinger perturbation theory, along with multicentered–multipole expansion method, has been employed to evaluate the long-range intermolecular interactions, while a “6-exp” potential function has been assumed for short-range interactions. The interaction energy values obtained through these computations have been taken as input to estimate the configurational entropy and Helmholtz free energy at room temperature, transition temperature, and above transition temperature. The present investigation provides valuable information in understanding the flexibility of a particular configuration at different temperatures. Further, it serves as a molecular model to yield the structure-phase stability relationship.

Keywords:

• CNDO/2 method
• configurational entropy
• interaction energy
• phase stability

Acknowledgments

The financial support rendered by the UGC, and CSIR, New Delhi, India is gratefully acknowledged.