Scientific Significance: Self-assembly of micro- or nano- objects at liquid-liquid interfaces is of tremendous interests in various natural and industrial applications. This project focuses on integrating research and education centering on heterogeneous and competitive self-assembly at liquid-liquid interfaces. First, the PI will investigate the self-assembly of heterogeneous colloidal lattices using Pickering emulsions as an experimental template. The two-dimensional colloidal lattices will contain colloidal particles of different wettability, size, and charge. Second, the PI will expand the concept of Pickering emulsions and use solid particles to stabilize double emulsions (self-assembly of single species solid particles at heterogeneous interfaces). They will investigate the influences of particle size, type, concentration, ionic strength, and oil/water ratio on the structure and stability of double emulsions stabilized by solid particles. Finally, they will study the heterogeneous or competitive self-assembly of nanoparticles and surfactants at liquid-liquid interfaces using a molecular dynamics simulation. They will simulate different concentrations of nanoparticles and surfactants at water-trichloroethylene interfaces as well as other pairs of liquid-liquid interfaces. This state-of-the-art research is of both fundamental and practical significance. Heterogeneous and competitive self-assembly at liquid-liquid interfaces is important in various natural and industrial processes. The proposed heterogeneous colloidal lattices are anticipated to open new ways to functionalize novel materials and to provide heterogeneous 2-D experimental model for condensed matter physics study. The expansion of Pickering emulsion concept to double emulsions is another innovative usage for particles and is anticipated to overcome the current major limitation of double emulsions that inhibited them from featuring in practical and commercial applications. The molecular dynamics simulations of heterogeneous or competitive self-assembly of nanoparticles and surfactants will provide in-situ and molecular information and a better fundamental understanding of the phenomenon that exists in many industrial processes such as oil recovery, multi-layer coatings, and emulsion technology.
Broader Impacts: The integration between research and education will be performed to meet the NSF's goals for two strategic outcomes: People and Ideas. With a strong commitment to education, the PI will establish research-related open-ended projects in the existing courses, promote undergraduate and graduate research, establish a new summer program to broaden the participation of under-represented groups, participate in the Teacher Training Institute, and promote technology transfer. Heterogeneous and competitive self-assembly at liquid-liquid interfaces are important and have widespread practical applications. Last, but not least, this project also provides a unique opportunity to meet the nation's need for a cutting-edge research area with the potential of significant expansion in the 21st century.
