Phase behaviour of the system 4′-pentyloxy-4-cyanobiphenyl + CO2

Isoplethic phase diagrams were measured for the system 4′-pentyloxy-4-cyanobiphenyl + CO2 for CO2 mole fractions up to 0.72, in temperature range 280–360 K and at pressures up to 12 MPa using a synthetic method with visual observation. It is found that pure 4′-pentyloxy-4-cyanobiphenyl shows two different solid phases, a nematic liquid phase (N) and an isotropic liquid phase (I2). For the binary system, liquid–liquid demixing (I1 + I2) was found. The following phase equilibria were measured: I2 + gas ↔ I2, N + gas ↔ N, solid + N ↔ N, solid + I2 ↔ I2, N ↔ N + I2 and N + I2 ↔ I2. Further, points of the three-phase curves (solid + N + gas), (N + I2 + gas), (solid + N + I2), (solid + I1 + I2) and (I1 + I2 + gas) were determined experimentally. Based on these measurements a P,T-projection of the system was constructed. At 341 K, the molar Henry coefficient of the isotropic phase was determined to be 13.7 MPa.

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► P,T-phase diagrams of a liquid crystal (pentyloxy cyanobiphenyl) with CO2 up to xco2 = 0.72.
► The liquid crystal + CO2 system shows liquid–liquid demixing.
► Pentyloxy cyanobiphenyl shows two solid phases which are enantiotropic.