Estimation of Mesophase Behaviour and Stability of Alkoxy Cyanobiphenyl Liquid Crystals: Lattice-Based Approach

The present study reports structure and phase behaviour of the alkoxy-cyanobiphenyl (nOCB) homologues particularly for 6OCB, 7OCB, 8OCB and 9OCB using semiempirical computational methods. Molecular structures were generated from crystallographic data obtained from literature. Charge distribution analyses were performed using AM1 and PM3 methods, to identify reactive sites and molecular stability. The overall reactivity order follows as 6OCB > 7OCB > 8OCB > 9OCB, suggesting reduced reactivity with increasing alkoxy chain length. Group charge analysis focuses on the dominant role of aromatic and end groups in influencing dipole interactions and phase stability. Interplanar spacing calculations for 3D, 2D and 1D systems reveal that improved molecular packing enhances thermal stability and phase transition behaviour with 8OCB exhibiting the highest nematic-isotropic (N-I) transition temperature. Smectic-A phases in higher homologues indicate increased structural ordering and polymorphism. Overall, the study validates a strong correlation between charge distribution, molecular packing, and phase transitions. PM3 results show greater consistency compared to AM1, providing improved reliability in predicting the behaviour of liquid crystal systems. The theoretical predictions are compared with experimental data from the literature, which demonstrates that latticebased approaches offer an efficient computational framework for analysing the role of alkoxy chain length on mesophase behaviour and stability.