Heat capacities and volumes of transfer of cholesteryl oleyl carbonate into various solvents

Heat capacities C_p and volumes V have been obtained at 25°C for the transfer of cholesteryl oleyl carbonate (ChOC) from a reference solvent, the highly-branched alkane 2,2,4,4,6,8,8-heptamethylnonane into various solvents. These include normal, branched, and cyclic alkanes as well as the pure cholesteric ChOC. V and most C_p are associated with the change of environmental free volume during the transfer process and are predicted by the Prigogine-Flory theory. However, for n-alkane solvents with more than twelve carbons, C_p is large, positive, and unattributable to free volume changes. It is consistent with a restriction of alkane segmental motion by the ChOC. The same mechanism has been proposed to explain an antiplasticization effect of ChOC on transitions in polymers.