In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Geraldine L. Richmond of the Department of Chemistry at University of Oregon, Eugene is studying molecular factors that contribute to nanoemulsion formation and stabilization by surfactants and polymers. Nanoemulsions are a class of colloids - mixture where a one component is suspended as tiny particles in another substance. Milk is an example of a colloid as small butterfat particles are dispersed in a watery liquid. Colloids provide exciting opportunities for a wide range of biological, medicinal, and technological applications. In these applications, colloids typically consist of oil-droplets that are stabilized in water solution by surface-adsorbed amphiphiles (compounds with water-loving and fat-loving properties). Their tiny diameters allow them to serve as vehicles for a wide range of compounds that are encapsulated in their interiors. In this research, scientists seek to understand the forces and energy required for surface adsorption and assembly of surfactants and polymers on spherical droplets of unique size. Molecular-level characteristics of these systems are investigated using a number of sophisticated measurement techniques. Knowledge associated with this research has the potential to impact drug delivery, food science, oil recovery and materials chemistry. The research team is broadening the impact of their research through educational outreach efforts aimed at a variety of ages and populations. The activities include public presentations and on-line videos for students and the general public on topics such as emulsions in our everyday lives, simple experiments in making and understanding emulsions, lasers in chemistry, and the special properties of nanoemulsions. Research lessons are incorporated into the outreach, networking, and educational activities through the "Water First!" project. This project involves working and collaborating with women scientists in Africa that are involved in water research, education and policy.
The research team is developing a detailed picture of the molecular characteristics of the nanodroplet surface that contribute to their formation and stabilization by surface adsorbed alkyl surfactants and polymers. The main objectives is twofold. First they want to fully characterize the molecular bonding, structure and orientation of emulsifying agents, oil and water at the surface of nanodroplets prepared in their kinetically stable state by ultrasonification. The scientists also compare the results with analogous studies of these emulsifying agents and their effect on interfacial oil and water at a planar oil-water interface that is in a thermodynamically stable state. The emulsifying agents chosen for these model studies are carboxylic acid containing alkyl surfactants and polymers. These fundamental studies are designed to take advantage of the adsorptive properties of these weakly acidic alkyl surfactants and polyelectrolytes whose surface charge and adsorptive characteristics can be varied by pH, ionic strength and metal ion complexation. Studies that involve the variation in length, size, hydrophobicity and rigidity of the adsorbates provide additional information related to surface packing, conformational ordering, and multi-layer formation. Both surface charge and steric effects are known to be important factors in reducing the pathway of these nanodroplets to coalesce and phase separate.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
