Associating fluids single association site

The density functional approach has also been used to study capillary condensation in slit-like pores [148,149]. As in the previous section, a simple model of the Lennard-Jones associating fluid with a single associative site is considered. All the parameters of the interparticle potentials are chosen the same as in the previous section. Our attention has been focused on the influence of association on capillary condensation and the evaluation of the phase diagram [42]. 

In the subsequent papers in the series, Wertheim extended his analysis to multiple association sites and to systems undergoing polymerization." His key contribution was to show that it is possible to obtain the properties of an associating or chain fluid based on knowledge of the thermodynamic properties (the Helmholtz energy and structure) of the monomer fluid. This is the basis of the now well-known Wertheim thermodynamic perturbation theory, and in turn, the basis of all SAFT equations of state. Interestingly, in this series of four papers, Wertheim did not present a single calculated result or any numerical tests of his proposed theories. 

Before discussing the more general case of associating fluids with multiple association sites, we will discuss the simpler case of molecules with a single association site A. For a single association site, the Mayer function is decomposed as... 

In what follows, attention will be restricted to the case that both s and d molecules have a hard spherical core Eq. (3), equal diameters, and the d molecules will be restricted to having a single association site. For this case, this mixture can be treated as a binary mixture of associating molecules in Wertheim s two-density formalism outlined in Section IV. As done throughout this chapter, we will consider a perturbation neatment with a hard sphere reference fluid. Like previous cases, the challenge is determining the graph sum Ac<">. 

Going beyond the single site case, the theory was recently extended such that the d molecules can have an arbitrary number of association sites [90]. In this approach the interaction between s molecules was also that of the hard sphere reference fluid. To add spherically symmetric attractions (square well, U, etc.) between s molecules, one simply needs to employ the appropriate reference system (square well, LJ, etc.). Work is currently under way to employ this association theory as a model for ion-water solvation. 

Mineral Oil Hydraulic Fluids. Studies regarding cancer in humans or animals after inhalation exposure to mineral oil hydraulic fluids were limited to a single case-control study that examined associations between subjectively reported occupational exposure to petroleum-derived liquids and cancer at particular sites among 3,726 male cancer patients (Siemiatycki et al. 1987a). The study found no convincing associations between occupational exposure to hydraulic fluids and cancer at any site. This study is discussed in more detail in Section 2.2.3.8, because, while inhalation exposure was probable for the subject occupations, the authors reported that the exposure route was more often dermal contact. 

To the author s knowledge, this approach has never been applied for numerical calculations of the structure or thermodynamics of one-site-associating fluids. Here we will show how a single simple approximation allows for the calculation... 

Single chain approximation— Neglects all graphs with more than one associated cluster. This is TPT, which assumes that the structure of unbonded sites in the fluid is similar to that of the reference fluid. The single chain approximation will fail, for instance, for fluids with a nanatic phase [68]. 

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