(191l) Molecular Modeling of Complex Fluids

Systems of complex fluids are characterized by the effects of multiple length scales on the fluid structure and physical properties. Equations of state are generally accurate for the homogeneous limit; however, parameter fitting strategies for highly non-linear equations of state such as the SAFT family can produce several equally good parameter sets -- especially with complex polar and/or hydrogen bonding fluids. Using intuitive assumptions of bulk fluid behavior based on experimental observation is presented as a methodology for determining the molecular parameters. This is demonstrated by fitting the intrinsic SAFT parameters of water and testing their robustness in predicting water solubility in normal alkanes. In addition, a single modeling framework is presented based on Wertheim's first order thermodynamic perturbation theory. The interfacial SAFT (iSAFT) density functional theory is capable of describing the inhomogeneities at surfaces and interfaces while reducing to the SAFT equation of state in the bulk. The accuracy of this model is used to describe the physical behavior and properties of a series of model oil-water-surfactant systems.