Comparative Study of Adsorption, Conformations, and Dynamics of Semi-Flexible Linear and Ring Polymers in...

Polymer conformation and dynamics are strongly influenced by the topology and chain rigidity. Understanding how these structural parameters influence the behavior of substrate-supported polymer films is of fundamental importance. Here, molecular dynamics simulations are performed to investigate semi-flexible linear and ring polymer films supported on attractive substrates, with a focus on comparing the effects of chain rigidity (k_θ) on their adsorption, conformation, and diffusion. Simulation results show that the adsorption properties of ring polymers and the substrate's suppression on their diffusion are weakly dependent on k_θ. While the adsorbed linear polymers change from random adsorption at low k_θ to fully adsorbed with localized ordered structure at high k_θ. The diffusion of linear polymers is strongly dependent on k_θ. At low k_θ, nonadsorbed linear polymers show a reduced diffusion in the substrate region due to the interaction with adsorbed polymers; in contrast, their diffusion is accelerated at high k_θ resulting from the formation of a dense adsorption layer, which screens the substrate's attraction. However, nonadsorbed ring polymers consistently exhibit reduced diffusion in the substrate region, with stronger dynamic suppression compared to linear polymers. Conversely, the substrate's influence propagates over a longer range in linear polymer films than in ring polymer films.