Percolation, Gelation, and Cluster Formation of Nanomaterials
Co-advised by Dr. Yun Liu, and Dr. Michael Mackay
Nanomaterials offer a wide variety of beneficial properties to applications in numerous facets of life. Suspensions of colloids, polymers, nanoparticles, proteins, etc. are found in products ranging from pharmaceuticals to paints to dish detergents. Typically, these materials exhibit a tendency to either remain stable as a homogeneously dispersed system of particles (repelling one another) or aggregate until they reach the point of precipitation or sedimentation (excessive attraction). However, certain materials offer intriguing behavior in that they will agglomerate to a specific size or number of particles and become stable. The underlying mechanism behind the formation of these "equilibrium" clusters is interesting for their applicability in numerous technologies. Specifically, this project will focus on the application of these materials in pharmaceuticals and organic based solar cells.
The underlying cause for cluster formation is a fine balance of attractive and repulsive forces on charged particles, which is typically represented by a potential function of varying complexity. The exact form of the potential and mechanism of particle-particle and cluster-cluster interactions are still undetermined. Adding to the complexity is the disagreement of results within literature between a thermodynamic and kinetic origin (and a range of different systems used to model these interactions). To determine an initial understanding of cluster dynamics, particle-particle interactions are being studied via Monte Carlo (MC), Molecular Dynamics (MD), and Stokesian Dynamics simulation efforts. Since the mechanism of cluster formation is still debated, these simulations will give insight into the thermodynamics and kinetics of such systems. Simulations will be accompanied by small angle neutron scattering (SANS) and neutron spin echo (NSE) experiments at the national center for neutron research (NCNR) at NIST in Gaithersburg, MD to corroborate simulation results. These experimental techniques provide characterization of nanometer length scales and nanosecond time scales. Experiments will focus on systems of lysozyme and PCBM as model pharmaceutical and organic solar cell systems.