  The mesophase behaviour of binary mixtures of bent-core and calamitic liquid
crystals is presented. The nematogenic 4,6-dichloro-1,3-phenylene
bis[4'-(10-undecen-1-yloxy)-1,1'-biphenyl-4-carboxylate] (I) was the
banana-shaped component. As the calamitic compound ethyl
4'-(9-decen-1-yloxy)-1,1'-biphenyl-4-carboxylate (II), similar to one arm of
the bent-core molecule, was used which exhibits smectic phases in a wide
temperature range. A total of 6 mixtures with different compositions were
prepared and studied by polarising optical microscopy, differential scanning
calorimetry and X-ray diffraction on non-oriented samples. In the mixtures a
nematic phase is not concomitant with smectic A phase, and the temperature
range of both phases highly depends on the concentration of the comprising
compounds. Lowered melting temperatures have been observed for all mixtures
with respect to that of the pure compounds. Unforeseen finding is the induction
of a monotropic SmC phase in mixtures with lowest concentration of the
bent-core compound. Semi-empirical quantum-chemical calculations have also been
performed. Based on the calculated molecular conformation, as well as on
collected X-ray diffraction data, a model for a possible self-assembly of the
banana-shaped and calamitic compounds is proposed.
