How does stiffness of polymer chains affect their adsorption transition?

Area of Science:

• Polymer Physics
• Materials Science
• Computational Chemistry

Background:

• Understanding polymer adsorption is key to designing advanced materials.
• Semiflexible polymers exhibit complex behavior due to chain stiffness and excluded volume interactions.
• Existing models like the wormlike chain and Kratky-Porod models have limitations in describing adsorbed polymer structures.

Purpose of the Study:

• To investigate the adsorption transition and structural properties of semiflexible polymers using molecular dynamics.
• To determine the influence of chain stiffness, length, and adsorption potential on polymer conformation.
• To identify the role of excluded volume interactions in adsorbed polymer behavior.

Main Methods:

• Coarse-grained molecular dynamics simulations of bead-spring polymers.
• Systematic variation of chain length (N), stiffness (κ, proportional to persistence length ℓ_p), and adsorption potential strength (ϵ_wall).
• Analysis of adsorbed monomer fraction, orientational order, and chain dimensions, with and without excluded volume interactions.

Main Results:

• Adsorption threshold (ϵ_wall^cr) scales with persistence length as predicted (ϵ_wall^cr∝ℓ_p^-1/3).
• Excluded volume effects are negligible for large persistence lengths near the transition but significant for strongly adsorbed chains.
• Orientational correlation length increases from ℓ_p to 2ℓ_p near the transition, deviating from 2D chain models due to excluded volume.

Conclusions:

• Excluded volume is essential for accurately describing the lateral dimensions of long, strongly adsorbed semiflexible polymers.
• The study provides insights into polymer adsorption phenomena relevant for experimental interpretation.
• Simulation results highlight the limitations of simplified models for complex polymer systems.