Transport of nanoparticles through complex fluids is essential for environment remediation strategies, nanocomposite processing conditions, and targeted drug delivery techniques. Nanoparticle transport is distinct from that of colloids for which dynamics are coupled to the bulk viscoelasticity of the surrounding fluids because nanoparticles are of comparable size to the heterogeneities present in many complex fluids. Thus, nanoparticle dynamics decouple from the bulk properties of the fluid and can transport many orders of magnitude faster than expected. To understand the underlying physics of transport in this size regime, we measure the dynamics of nanoparticles moving through polymer solutions, which serve as model complex fluids with well-controlled and tunable heterogeneities. The long-time dynamics of the nanoparticles couple to the polymer relaxations, resulting in strong deviations from Stokes-Einstein predictions that depend on particle size and polymer concentration. Nanoparticle dynamics in polymer solutions are further modified through surface modifications, specifically electrostatic charges or grafted polymers. Grafted polymers help to stabilize the nanoparticle dispersions but their conformations can be perturbed by the dissolved free polymer. These perturbations have significant implications for the structure and dynamics of the polymer-grafted nanoparticles. Tuning the nanoparticle size and modifying the particle surface chemistry grants excellent control over the transport properties of nanoparticles through complex media.

Structure and dynamics of nanoparticles in polymeric fluids

255th National Meeting (2018)

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