Thermodynamic characteristics of a dimer liquid crystal comprising a relatively long spacer -O(CH2CH2O)(6)- were investigated. The contour length of the flexible spacer (similar to 25 angstrom) exceeds that of the hard segments (similar to 18 angstrom). The compound exhibits a nematic mesophase (N) between the crystal (C) and the isotropic melt (I) over a sizably wide temperature range (similar to 80 degrees C). Thermodynamic quantities such as thermal expansion coefficient alpha, isothermal compressibility beta, thermal pressure coefficient gamma (=alpha/beta), and the volume change Delta V at the CN and NI interphase were carefully determined by the PVT measurements. The transition entropies due to volume expansion were estimated by the well-known relation Delta S-V = gamma Delta V. The latent entropies (Delta S-tr)(P) for both CN and NI transitions were estimated according to the Clapeyron relation from the PVT and DTA data. The magnitude of the constant-volume entropy changes (Delta S-tr)(V) calculated was found to be about 50-60% of the corresponding values of (Delta S-tr)(P). These results were consistent with the previous H-2 NMR observations that the chain segments adopt a nematic conformation in the LC state. The thermodynamic role of the flexible segment in determining the phase transitions has been critically discussed.