A study on the diffusivity of polymers in crowded environments with periodically distributed nanoparticles.

The effect of nanoparticles (NPs) on the diffusivity of polymers in crowded environments is complicated. We study the diffusivity of polymers in the environment with periodically distributed immobile NPs by using off-lattice Monte Carlo simulations. Results show that the diffusion coefficient D of polymers at low temperature is dependent on the inter-particle distance d and polymer length N or end-to-end distance of polymers in dilute solution R. At low temperature, D is large at both small and large d and a minimum is observed at intermediate d. The nonmonotonic behavior of D is due to the reason that there are two kinds of diffusion modes for the polymers at low temperature: NP-exchange motion for R > d and adsorption-and-desorption motion for R < d. Moreover, we observe the oscillation of D with N at a relatively low temperature. The novel behavior is relevant to the adsorption of polymers on NPs and is explained from the free energy barrier for polymers jumping from the ground state to others.