Diffusion Mode Transition between Gaussian and Non-Gaussian of Nanoparticles in Polymer Solutions

Abstract

The dynamic density functional theory is applied to study the diffusion of nanoparticles in polymer solutions, in which different diffusion modes have been identified by exploiting the density and free energy evolutions. Under the condition of low polymer concentration, diffusion is controlled by particle free motion with a normal Gaussian type. As the concentration increases, the non- Gaussian behavior can be observed when the particle size is comparable to the correlation length of polymer chain. Particles need to penetrate through a cage and overcome an entropic barrier, where the hopping and the model-coupling diffusion coexist. Further increase of polymer concentration can result in complete restriction of the particle by surrounding polymer segments. In this case, the non-Gaussian process fades away, and particle diffusion is controlled by Rouse dynamics of polymer chains with the generalized Gaussian characteristics.