THERMODYNAMIC INTERPRETATION OF THE TERMINAL GROUP EFFECT ON THE THERMAL-STABILITY OF A MESOPHASE

Nematic liquid crystal-isotropic liquid transition temperature-composi tion curves were calculated for the four binary systems between p-azox yanisole and Schiff bases. The calculation was done by means of equal G analysis, which is one of the thermodynamic treatments reported by V an Hecke. Two Schiff bases with nitro group were chosen as examples of convex upwards transition temperature-composition curves. Two Schiff bases with dimethylamino group were chosen as examples of Concave upwa rds transition temperature-composition curves. As a result, deviations from linearity, which have been interpreted so far as due to the inte raction between the component compounds, were attributed to the differ ences between the nematic liquid crystal-isotropic liquid transition e ntropies of p-azoxyanisole and a schiff base.