Predicting the Morphology and Viscosity of Microemulsions Using the HLD-NAC Model

This work focuses on extending the HLD-NAC model to help predict the shape and viscosity of SDHS toluene water microemulsions from readily available formulation parameters. To do so, a new shape-based NAC model was introduced which relates the net and average curvatures to the length and radius of microemulsion droplets possessing a hypothesized cylindrical core with hemispherical end caps. Knowing the shape of these droplets, theoretical scattering profiles and maximum hydrodynamic radii were predicted. Furthermore, considering the predicted volume fraction of the dispersed droplets alongside the shape allows for the accurate prediction of the microemulsion viscosity. It was found that treating the microemulsion phase as a dilute suspension of rigid rods yielded predicted viscosities close to the experimental values near the bicontinuous phase transition limits. These correlations were further extended to published experimental data with regard to the viscosities of nonionic surfactant systems. The predicted microemulsion morphology and viscosity may be useful in the design of formulations for nanoparticle synthesis, enhanced oil recovery, and various environmental remediation technologies.