On the nature of the smectic mesophase in 8CB + 10CB binary mixtures. Evidences for a smectic A to nematic tricritical point

The two-component system octylcyanobiphenyl(8CB) + decylcyanobiphenil(10CB) has been studied by means of Modulated Differential Scanning Calorimetry, optical microscopy and X-ray diffraction. Although the general trends of the phase diagram are similar to that proposed by Marynissen et al., additional evidences for the existence of TCP have been reported, the composition being about 0.2, which is slightly lower than that proposed in the aforementioned work. Additionally, the smectic mesophase of the 8CB + 10CB mixtures has been characterised through X-ray diffraction and optical measurements as smectic A for the whole composition range. Such a result is against the recent work of Oweimreen and Hwang.