Emergence of Mixed Nematic Mesophase in Binary System of a Non-Mesogen and a Smectogen

An interesting binary system consisting of a non-mesogen and a smectogen viz. p-chlorophenyl-p′-methoxycinnamate (A) and p-chlorophenyl-p′-n-octyloxycinnamate (B), respectively, which belong to the same homologous series1 viz. p-chlorophenyl-p′-n-alkoxycinnamates is now reported in which mixed monotropic nematic and mixed enantiotropic nematic mesophases emerge over a wide range of temperature and concentration. It is observed that the mixed smectic mesophase gets depressed as the concentration of the non-mesogen increases, yielding simultaneously enantiotropic mixed nematic phase; the mixed phase diagram exhibits nematic as well as smectic phases. As the concentration of the non-mesogen increases further, the mixed smectic phase enters into monotropic state while the mixed nematic phase continues to be enantiotropic. However, with more than about 60 mole% (A), the mixed nematic enantiotropic mesophase becomes monotropic nematic which ends by about 92 mole% of the non-mesogen (A). The characteristic modifications in the mixed mesomorphism are correlated with the structural characteristics of the components of the molecular forces displayed by them.