Phase behaviour and applications of a binary liquid-liquid mixture of methanol and a thermotropic liquid crystal

Herein, we report on the phase behaviour of a binary liquid-liquid mixture composed of methanol (MeOH) and the thermotropic liquid crystal 4-Cyano-4'-pentylbiphenyl (5CB). The corresponding phase diagram combines features of a conventional liquid-liquid mixture with characteristics that are particular to the nematic liquid crystal. We observe four arrangements as a function of composition and temperature, namely monophasic isotropic, monophasic nematic, biphasic isotropic-isotropic and biphasic isotropic-nematic, with an upper critical solution temperature of 298 K. The interplay of nematogenic and non-nematogenic species offers a number of applications. Dilution of mesogens with MeOH allows to control the isotropic-to-nematic phase transition of 5CB over a range of 35 K. The tunability of phase mixing and phase composition in an accessible temperature window provides novel routes for the extraction of target compounds, here shown for Eosin Y, Doxorubicin, Crystal Violet and Sudan IV.