Associated perturbed anisotropic chain theory

The Associated-Perturbed-Anisotropic-Chain-Theory and the Gradient Theory... 

In the present section we treat the interfaces of mixtures in which there may be one or more associating component(s). For this purpose, the gradient theory is combined with the Associating Perturbed Anisotropic Chain Theory (APACT) which takes into account the possibility of association. In this section only association due to hydogen bonding is considered. The results are also compared with the results obtained with the gradient theory combined with the PR equation of state. 

As was pointed out earlier, the gradient theory can be linked easily to a semi-empirical equation of state. The equations of state applied in this study are the Peng-Robinson equation of state and the Associated-Perturbed-Anisotropic-Chain-Theory (APACT). The only effect on the interfacial tensions of pure fluids that is strongly influenced by the selected equation of state is the behavioitr in the near-critical region, since other differences are completely annulled by the fitting procerdure that is applied for the influence parameter. 

Ikonomou, G.D., and Donohue, M.D. (1986) Thermodynamics of hydrogen-bonded molecules the associated perturbed anisotropic chain theory, AJChEJ. 32, 1716-1725. 

In this section, we present the results that have been obtained by the implementation of the Associated-Perturbed-Anisotropic-Chain-Theoiy (APACT) into the gradient theory of van der Waals. Not all details and equations of the APACT will be shown, because they are described in detail elsewhere [19,20,21]. 

The first models used to describe hydrogen bonding fluids were developed using a chemical approach, where each associated cluster is treated as a distinct species created from the reaction of monomers and smaller associated clusters [8,9]. The reactions are governed by equilibrium constants that must be obtained empirically. This type of approach has been incorporated into various equations of state including a van-der-Waals-type equation of state [10], the perturbed anisotropic chain theory equation of state (APACT) [11], and the Sanchez-Lacombe [12] equation of state. 

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