47236-AC6
Development of a Density Functional Theory for Copolymer and Surfactant Interfacial Properties and Microstructure
Our group is developing a novel density functional theory for multi-scale modeling of complex fluid assemblies and applying the theory to several critical problems in nanostructured media. This research builds on our polymer density functional theory (DFT) that has shown great promise for predicting interfacial properties and microstructure of copolymer solutions and blends.
Initial focus in the research has been modeling the phase behavior of water / hydrocarbon mixtures in the bulk and studying the interfacial properties and micro-structure of model surfactant molecules at the interface of two immiscible fluids as a model of an oil / water / surfactant system.
The phase behavior of water / hydrocarbon mixtures is fundamental to understanding how hydrogen bonding and compressibility affects fluid properties. Modeling of the interfacial properties and meso-scale structure of fluids depends on an accurate model of bulk fluid phase behavior. We have developed a predictive model of water solubility in hydrocarbon systems from methane to polymers over a wide range of temperature and pressure. Using the model, we identify suspicious experimental data sets and predict water content at conditions and for systems where no data is available.
From self-assembly to form nanostructured materials to enhanced oil recovery, predictive modeling of mixed surfactants for oil / water / surfactant systems is a challenge. We believe that extensions of our density functional theory can meet this challenge by providing predictive modeling and physical insight. We begin by considering a simple model was first proposed by Telo da Gama and Gubbins. The “oil” and “water” molecules are represented by attracting spheres. The “oil-water” interaction is only repulsive. The surfactant molecules are represented as a chain of these same “oil” and “water” beads bonded together. Using such a model, we are studying the effect surfactant structure (including the number of beads of each type, bead position, and branching) on interfacial tension and the structure of the interface. Preliminary results have shown excellent agreement with molecular simulation results for the interfacial tension and the molecular structure of the interface.
