The diagrams of state have been studied for some liquid crystal mixtures which show the induction of smectic phases. Each of the systems studied contains one component with an amino group which influences the polarity and the electron donor property of the molecules. The discussion of the diagrams of state, of the thickness of the smectic layers and of the colours of the mixtures, which indicate the formation of CT complexes, shows that existing models can not explain the induction of smectic phases.
The diagrams of state of mixtures of 4-n-alkyloxybenzylidene-4'-n-butylanilines with 4-n- alkyl- and 4-n-alkyloxy-4'-cyanobiphenyls are studied. The mixtures form induced smectic phases of type SA, SB and SE. In all three smectic phases the thickness of the smectic layers agrees with the mean values of the molecular lengths. In most cases the induced SA phases do not show uninterrupted miscibility with the SA phases of the pure components. For instance, the system 40 • 4/8 CBP exhibits three separate SA phase areas. The maximum transition temperatures of the induced smectic phases increase with increasing chain length of the azomethines, but remain constant in case of the SA and SB phases or even decrease in case of the SE phases with increasing chain length of the cyanobiphenyls