Interfacial phenomena are of vital importance to industrial and commercial applications from enhanced oil recovery to personal care products. To optimize interfacial processes, amphiphiles are usually involved, and, unlike simple molecules, amphiphiles possess both hydrophilic(water-loving) and hydrophobic(oil-loving) properties. Compared to the knowledge gained regarding the properties of simple fluids in the bulk region, our knowledge of modeling and prediction of the phase behavior and interfacial properties of amphiphiles is relatively less abundant. The goal of this thesis is to enhance our understanding of the phase behavior and interfacial phenomena of the systems containing amphiphiles using molecular simulation and statistical mechanics based theories. In particular, we have studied fundamental aspects related to enhanced oil recovery, i.e. interfacial tension, micelle formation, middle-phase microemulsion, foam stability and wettability alteration of reservoir rock surfaces.

In this thesis, the interfacial Statistical Associating Fluid Theory that relies on fundamental measure theory, mean field treatment of van der Waals interaction, and Wertheim's thermodynamic perturbation theory for association and chain connectivity along with molecular dynamics simulation have been used to study the molecular structure and interfacial properties of surfactant containing systems. Key contributions of this thesis include:

First, an approach inside iSAFT framework based on the Method of Moments that predicts the formation of middle-phase microemulsions of surfactant/oil/water systems has been presented.

Second, the iSAFT approach has been extended to model surfactant micelle formation. Complete interfacial tension isotherm can be predicted. The effects of surfactant architecture have been studied.

Third, the role of lauryl betaine as a foam booster was investigated. Insight was gained on the interaction between lauryl betaine and alpha olefin sulfonate.

Fourth, the adsorption of deprotonated naphthenic acid on Calcite surface was studied, which is important in understanding the wettability alteration of carbonate reservoirs.