DETAILED THERMAL STUDY OF THE ROTATOR PHASE OF PURE HEPTACOSANE (N-C27H56) BY ALTERNATING-CURRENT CALORIMETRY

The dynamic heat capacity of heptacosane was measured by ac calorimetr y. Samples with a homologous purity of 99.9% were used. The characteri stic feature of ac calorimetry of excluding latent heat made it possib le to study details of the dynamic heat capacity of the rotator phase. In both the heating and cooling processes at a constant rate of 0.5 K /min, slow motion with a correlation time comparable to 1/3 s was obse rved. At constant temperatures of the rotator phase significant and sl ow annealing effects were observed. Experimental results showed that t he equilibrium state at temperatures equal to or higher than 329.9 K w as apparently different from the equilibrium state at temperatures equ al to or lower than 329.5 K. It was shown that the observed experiment al results could be explained by assuming existence of a parameter whi ch changes only very slowly.