Abstract
Heat capacity of a 20 g sample of the mesogen 4-cyanobenzoyloxy-4′-octylbenzoyloxy-p-phenylene was measured in the temperature range 380 to 510 K by adiabatic calorimetry. The C p versus T data is interpreted in terms of thermodynamically equivalent SA1 and SAd phases whose Gibbs potential surface intersects the thermodynamically equivalent reentrant nematic and nematic Gibbs potential surface in such a way as to define the first order doubly reentrant phase sequence: SA1-N-SAd-N. The data do not allow any precise estimates of transition enthalpies.