Dynamics of Nanoparticles in Complex Media



Journal Title

Journal ISSN

Volume Title



Hindered mobility of nanoparticles in complex media is ubiquitous in drug delivery, in processing of polymer nanocomposites, and in extraction of hydrocarbons. These applications require nanoparticles suspended in non-Newtonian fluids to be controllably dispersed through complex porous media. In this dissertation, the role of non-Newtonian fluid characteristics on mobility of nanoparticles through complex media is studied. First, the diffusive mobility of nanoparticles in solutions of a high-molecular weight polyelectrolyte, partially hydrolyzed polyacrylamide, is measured to determine the role of polymer concentration on the local dynamics of nanoparticles. Above the polymer overlap concentration, nanoparticle mobility exhibits subdiffusive behavior at short time scales. The dynamics approach Fickian diffusion at longer time scales and at all concentrations but deviate from predictions made from the bulk viscosity of the polymer solutions. These results indicate that particle dynamics are coupled to the polymer dynamics and highlight the importance of segmental motion of polymer chains on the long-time diffusivity of nanoparticles whose size is comparable to typical polymer length scales. Second, the diffusive mobility of nanoparticles suspended in Newtonian and non-Newtonian solutions within porous media is studied to separate the effects of confinement mediated by macromolecules and by geometric obstacles on diffusion of nanoparticles. Diffusive mobility decreases as nanoparticles are increasingly hindered by spatial confinement due to hydrodynamic interactions with the porous medium. In non-Newtonian solutions, temporary adsorption of particles onto the surface of glass beads due to depletion interactions further reduces the diffusive mobility of particles. Finally, the effects of flow properties, fluid characteristics, and geometric confinement on dispersion of particles through mono and bidisperse porous media are studied. The long-time dispersion coefficients of nanoparticles in longitudinal and transverse direction scale linearly with Pe number across a range of solution flow rates and pore sizes, independent of the fluid rheology. This suggests that random mixing effectively averages out the velocity fluctuations so that the non-Newtonian fluid characteristics do not affect long-time dispersion. Moreover, average transport properties do not depend on distribution of pore size within the beds. Overall, this dissertation improves our essential understanding of hindering factors affecting dynamics of nanoparticles through complex media.



Nanoparticle, Hindered diffusion, Transport, Dispersion, Complex media, Polymer solution, Porous media


Portions of this document appear in: Babaye Khorasani, Firoozeh, Ryan Poling-Skutvik, Ramanan Krishnamoorti, and Jacinta C. Conrad. "Mobility of nanoparticles in semidilute polyelectrolyte solutions." Macromolecules 47, no. 15 (2014): 5328-5333.