Van der Waals theory of nematogenic solutions. II. Application to binary solutions with spherical solutes and rodlike solvents

The Van der Waals theory of nematogenic solutions derived in Paper I of this series is here applied to binary mixtures with effectively spherical solute molecules and rodlike solvent molecules. Predicted temperature-mole-fraction phase diagrams are shown to be in rather good agreement with experimental data for the systems CCl₄-p, p^'-dihexyloxyazoxybenzene (DHAB), (CH₃)₄Sn-methoxybenzylidene n-butylaniline (MBBA), (C₂{H}₅$)$₄Sn$-MBBA, (${C}₃H₇)₄Sn-MBBA, and (C₄{H}₉$)$₄Sn$-MBBA. On the basis of these calculations, it is argued that when a more or less spherical solute is added to a nematic mesophase, the onset of the nematic{→}isotropic phase transition is controlled primarily by excluded-volume effects and the overall strength of the intermolecular attractions in the system.