Effect of molecular structure on the phase behaviour of some liquid crystalline compounds and their mixtures XI. Binary mixtures of unsymmetrical 1,4-phenylene bis-(4-substituted benzoates)

Binary mixtures formed from components of the four series of unsymmetrical 1,4-phenylene bis-4-substituted benzoates, in which one substituent is a terminal alkoxy group with a number of carbon atoms kept constant (at n =6, 8, 14 and 16) while the other substituent (X) ranges through CH₃O, CH₃, Cl, CN and NO₂, were prepared and characterized for their mesophase behaviour. Transition temperatures of the mixtures prepared were measured by differential scanning calorimetry and identified by polarizing optical microscopy. Phase diagrams for the various binary combinations were constructed to investigate the dependence of the phase behaviour of mixed systems upon the electronic nature of the terminal group X, as well as on the chain length of the alkoxy group. The results are discussed in terms of mesomeric and polarizability effects.