Computer simulations of ordering in homologous series of p-n-alkoxybenzoic acids (nOBAC) at nematic-isotropic transition temperature - role of dielectric medium

摘要

Computer simulations of molecular ordering in nematogenic p-n-alkoxybenzoic acids has been carried out with respect to translatory and orientational motions for the acids having 7 (7OBAC); 8 (8OBAC) and 9 (9OBAC) carbon atoms in the alkyl chain. The net atomic charge and atomic dipole components at each atomic centre of the molecule has been evaluated using the CNDO/2 method. The configurational energy has been computed using the Rayleigh-Schrodinger perturbation method. The total interaction energy values obtained by these computations were used to calculate the probability of each configuration in a dielectric medium (i.e., non-interacting and non-mesogenic solvent, benzene) at phase transition temperature using the Maxwell-Boltzmann formula. The flexibility of various configurations has been studied in terms of variation of probability due to small departures from the most probable configuration. The various possible geometrical arrangements between a molecular pair during the different modes of interactions have been considered. An attempt has been made to develop a new and interesting model of nematogens in dielectric medium. (C) 2004 Elsevier B.V. All rights reserved.