Translational and Rotational Diffusions of Nanorods within Semidilute and Entangled Polymer Solutions

Nanoparticle transport through macromolecular fluids plays important roles in several interdisciplinary fields of studies ranging from polymer science to drug delivery. But the diffusion of asymmetric nano-objects, such as rods, through polymer solutions is poorly understood in spite of their growing applications. Here by using a novel multiphoton fluctuation correlation spectroscopy (MP-FCS) technique, we investigated the translation and rotational diffusion of gold nanorods (AuNRs) in polyethylene glycol (PEG) solutions of varying volume fraction and molecular weights. We determined the nanoviscosity experienced by the NRs and compared it with the theoretical studies of nanosphere diffusion in semidilute and entangled polymer solutions. Our results showed the importance of nonhydrodynamic friction and the effects of polymer dynamics in determining the transport of the nanoparticles.