Nematic Phases Created in Binary Mixtures of Smectics A

Abstract It is shown that the forming of nematic mixtures composed uniquely of compounds with the smectic phase A is possible. The nematic phase is created as a result of the weakening of intermolecular attraction forces in the disturbed smectic layers. Many examples are given of binary mixtures in which induction of the nematic phase is observed or an enhancement of the nematic phase at the cost of the smectic phase takes place. The effect of the molecular structure and of the properties of the smecticphase A on its destabilization in a mixture and the creation of the nematic gap between the smectic A regions are discussed. The most characteristic features of the phase diagrams related to the S→I and S→N phase transitions and the accompanying changes of enthalpy of these phase transitions, of density and viscosity are shown in detail by way of example of binary mixtures composed of 5-n-alkyl-2-(4′-isothiocyanatophenyl)-1,3-dioxanes (smectic A1) and 80CB, or 120CB or 12CB (smectic Ad). Keywords: liquid crystalspolar smectic mixturesinduced nematic phasesdioxanesbiphenylsesters