Thermodynamic measurements on the binary system bis{[2,2-di(n-hexyloxycarbonyl)ethenyl]phenyl} biphenyl-4,4 '-dicarboxylate and 4-n-octyloxyphenyl 4-n-pentyloxybenzoate at elevated pressures

Thermodynamic measurements have been carried out on the binary system of a swallow-tailed liquid crystal A = bis{[2,2-di(n-hexyloxycarbonyl)ethenyl]ph enyl} biphenyl-4,4 ' -dicarboxylate (4DS6) and B = 4-n-octyloxyphenyl 4-n-p entyloxybenzoate (5O/O8). A filled smectic A phase is induced in the concen tration range 0.11 < x(A) < 0.75. The maximum of the SmA-N transition tempe rature (365 K) is observed for x(A) = 0.33. Dilatometric measurements show that the packing density in the filled phases is increased. High-pressure D TA is employed in order to investigate the coexistence range of the liquid crystalline phases and the slopes of the transition lines. The slopes of th e melting curves for the mixtures are significantly smaller than those for the pure components. The slopes for the smectic - nematic - isotropic trans itions are considerably larger. The coexistence range for the (smectic + ne matic) phases does not seem to be pressure-limited, rather it increases wit h pressure.