Interfacial curvature of surfactants

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The long-term goal of this interfacial curvature program is to develop a framework to predict the phase behaviour and dynamics of surfactant-oil-water (SOW) systems. This knowledge would enable using a chemical engineering approach (mass and energy balances, thermodynamics, reaction kinetics and transport phenomena) to design process and products that involve surfactants, including microemulsions, emulsions, suspensions, foams, and others. At the core of this program is the hydrophilic-lipophilic-difference (HLD) + net-average curvature (NAC) model, a semi-empirical equation of state for SOW systems. This grant application seeks support to advance the HLD-NAC framework in the following priority areas: supercriticial fluids, prediction of ternary phase diagrams (including polymers and liquid crystals), and the prediction of dynamic interfacial phenomena (solubilisation, interfacial tension and wetting). These priorities areas were identified in consultation with academic and industrial collaborators. The work on supercritical fluids is motivated in part by encouraging data from novel CO2 microemulsion stimulation of depleted oil reservoirs, CO2-based dry cleaning, and CO2 microemulsion synthesis of nanoparticles used in pharmaceutical applications. The behavior of these systems is highly non-linear and there are phase inversion changes that take place within narrow temperature and pressure intervals, leading to substantial changes in the performance of these technologies. The original HLD equation does not account for changes in pressure, thus the need for an alternative HLD based on molecular interactions that can account for changes in pressure and temperature and that could help engineer these CO2 microemulsion processes. The work on ternary phase diagrams was motivated by colleagues in the oil and gas industry, in the pharmaceutical and food industries, in the paint/coatings industry, and in the surfactant and detergents industry. Experimentally-obtained ternary phase diagrams are highly resource-intensive but they are the ultimate formulation tool for all these industries. The work on dynamic phenomena is motivated by the need to predict the efficiency of surfactant-based extraction processes (self-emulsified solvent injection, extractive solubilisation, solubilisation swings, extractive self-emulsification, and alkaline surfactant polymer flooding for tertiary oil recovery). Our recent work on emulsions showed that separation times could vary by as much as four orders of magnitude by simply changing the type of surfactant. We hypothesize that such drastic changes could also translate to other separation process, and their understanding and management will lead to more efficient processes. The work on the molecular basis of HLD and its application to supercritical systems will be undertaken by Mr. Boza-Troncoso (PhD candidate) who introduced and validated the integrated free energy model (IFEM) to predict the behaviour SOW systems. The work on ternary phase diagrams will be a team effort between Mrs. Zarate (PhD candidate) and Mr. Nouraei (PhD student). The work on interfacial dynamics will be undertaken by Mr. Stamitti (PhD applicant). Based on previous outcomes of this research program, we expect that the findings from these studies and the highly qualified personnel trained (4 PhDs and 10 or more undergraduates) will be in demand by companies involved in the production of nutraceuticals ($4 billion/year industry in Canada), in cosmetics and personal care products ($9 billion/year industry in Canada), in the pharmaceutical industry($20 billion/year industry in Canada), and in the oil and gas industry ($80 billion/year industry in Canada).