Inconsistency of Diffusion and Relaxation of Ring Polymers Adsorbed on Rough Surfaces

Area of Science:

• Polymer Physics
• Soft Matter Physics
• Surface Science

Background:

• Ring polymers possess unique topological constraints due to their closed architecture.
• Adsorption onto surfaces, especially rough ones, significantly influences polymer dynamics.
• Understanding diffusion and relaxation is crucial for polymer behavior prediction.

Purpose of the Study:

• To investigate the diffusion and relaxation dynamics of single ring polymers adsorbed on rough surfaces.
• To elucidate the role of surface roughness and polymer size on dynamics.
• To explore the interplay between topological constraints and surface interactions.

Main Methods:

• Molecular dynamics simulations were employed to model the system.
• Analysis focused on diffusion coefficients and relaxation times.
• Key parameters included surface roughness, obstacle distance, and polymer size (lateral chain size).

Main Results:

• Surface roughness induces a discrepancy between diffusion and relaxation in ring polymers.
• For larger polymers (lateral chain size > obstacle distance), anchoring to obstacles reduces diffusivity but not relaxation.
• At even larger sizes, polymers exhibit hopping diffusion, while relaxation follows reptation-like dynamics, decoupling diffusion and relaxation.

Conclusions:

• The topological constraint of ring polymers on rough surfaces leads to a unique inconsistency between diffusion and relaxation.
• This decoupling is dependent on the polymer's lateral chain size relative to surface obstacle distance.
• Findings offer insights into the fundamental physical nature of adsorbed ring polymers and potential applications.