Gibbs energy of aggregation: An integral thermodynamic characteristic of the self-organization of equilibrium liquid systems

The Gibbs energy of aggregation, a new integral thermodynamic characteristic of the self-organization of equilibrium liquid systems due to specific interactions such as hydrogen bonds, is introduced. This function is defined as the difference between the Gibbs energy of the associated liquid system and the Gibbs energy of the hypothetical nonideal liquid system consisting of monomers at the same temperature and pressure. General expressions for molar Gibbs energies of aggregation of a pure liquid and a binary solution, taking into account the contributions from specific and universal (dipole, dispersion) interactions, are derived in the context of the quasi-chemical approach. An expression for the dependence of the Gibbs energy of aggregation of a pure liquid on the degree of chain aggregation is derived using the athermal associated solution model. In the same approximation, an expression for the dependence of the Gibbs energy of aggregation for a binary solution of an associating component in an inert solvent on the solution’s composition and the degree of the chain association of a pure liquid is derived. Results from numerical calculations of the Gibbs energies of aggregation of a pure liquid and a binary solution are reported. A correlation is made between the Gibbs energy of aggregation of a pure liquid and the standard Gibbs energy of formation of the dimer. It is shown that the Gibbs energy of aggregation versus the standard Gibbs energy of dimerization dependence is nonlinear in the range of low degrees of aggregation.