Low-temperature heat capacities and thermodynamic functions of four-ring chain difluoromethyleneoxy liquid crystalline compounds with different alkyl terminal chain

The heat capacities of three difluoromethyleneoxy liquid crystalline compounds (n-BB(F)B(F,F)XB(F,F)-F; n = 3, 4, 5) were measured using a quantum design physical properties measurement system (PPMS) based on a heat-pulse relaxation method in the temperature range from 1.9 to 300 K. The experimental results showed that the heat capacities of these three compounds increased with the temperature increment and none of the thermal anomalies were observed in the entire temperature region; and also the heat capacity values of n-BB(F)B(F,F)XB(F,F)-F (n = 3, 5) are larger than those of 4-BB(F)B(F,F)XB(F,F)-F due to the odd–even carbon effect below 21 K. The standard molar entropies at 298.15 K and 0.1 MPa were determined to be (631.14 ± 6.31), (650.21 ± 6.50), and (697.49 ± 6.97) J K−1 mol−1 for n-BB(F)B(F,F)XB(F,F)-F (n = 3, 4, 5), respectively.