A nematic phase created in mixtures of polar smectics The effect of smectic layer properties

Phase diagrams of binary mixtures composed of compounds with the NCS terminal group (n-DBT, n-PBT, n-TPB (smectic A₁) or n-BT (smectic E₁)) and n-OCB, n-CB (smectics A_d) are presented. It is shown that the width of the nematic gap that separates the A₁ or E₁ phase region from the smectic A_d phase is related to the interaction energy of the molecules in the smectic layers and to the difference in the smectic layer spacings.