Static and dynamic properties of a semiflexible polymer in a crowded environment with randomly distributed immobile nanoparticles

Molecular dynamic simulations are performed for semiflexible polymers in a crowded environment with randomly distributed immobile nanoparticles (NPs). Herein, the effects of chain stiffness (kθ), polymer–NP interaction (εPN), and concentration of NPs (CNP) on the static and dynamic properties of the polymers have been studied. The mean square radius of gyration 〈RG2〉 can be increased, decreased, or unchanged depending on these three variables. For a fully flexible polymer (kθ = 0), 〈RG2〉 changes non-monotonously with εPN and CNP. However, for a semiflexible polymer (kθ = 10 with its persistence length larger than the inter-particle distance of the NPs), 〈RG2〉 decreases monotonously or remains unchanged with an increase in εPN or CNP; this indicates the softening of polymer by the NPs. Moreover, the translational diffusion and rotation of the polymer are retarded by the NPs. Subdiffusion is observed for both the fully flexible polymer and semiflexible polymer at a sufficiently large εPN. The effect of NPs on the translational diffusion is more obvious for the fully flexible polymer because more monomers are in contact with the NPs in the fully flexible polymer. In contrast, the effect of NPs on rotation is more obvious for the semiflexible polymer because it is in contact with more NPs. Furthermore, the rotational relaxation time τR of the semiflexible polymer increases faster with an increase in εPN or CNP than that of the fully flexible polymer.