Effect of molecular structure on the phase behaviour of some liquid crystalline compounds and their mixtures - VIII. Quaternary mixtures of enantiotropes

Transition temperatures of quaternary mixtures prepared from the cyano and nitro derivatives of the two series, 4-hexadecyloxyphenyl 4-substituted ben zoates (Ia,b) and 4-substituted phenyl 4-hexadecyloxy benzoates (IIa,b) hav e been determined by DSC and the transitions identified with polarized ligh t microscopy. The cyano and nitro derivatives, in both series, were used be cause their molecules are enantiotropic. The method described before for th e ternary system was extended to elucidate the eutectic composition of the quaternary system from the knowledge of either the eutectic compositions of the four possible ternary mixtures or of those of the six individual binar y systems. A general equation was deduced to calculate the eutectic composi tion of any multi-component system from values determined for their individ ual binary systems. T-c values of binary, ternary, or quaternary mixtures w ere related to the polarizability anisotropy, Delta alpha(X), of the indivi dual C-Ar-X bonds. The mixture law was successfully applied.