Long Tails with Flower-like Conformations Undergo an Escape Transition in Homopolymer Adsorption Layers

Area of Science:

• Polymer Physics
• Surface Science
• Computational Chemistry

Background:

• De Gennes predicted homopolymer adsorption profiles with proximal, central, and distal regions.
• For good solvents, the central region was predicted to have a self-similar structure with a density profile decaying as a power law (-4/3).

Purpose of the Study:

• To investigate the complex central region of homopolymer adsorption profiles.
• To reconcile numerical self-consistent field (SCF) predictions with de Gennes' theory.
• To understand the role of chain tails and loops in the adsorption profile.

Main Methods:

• Numerical self-consistent field (SCF) calculations for long polymer chains (N).
• Analysis of density profiles and chain conformations within the adsorption layer.
• Identification of distinct regions dominated by loops and tails.

Main Results:

• SCF predictions reveal a more complex central region than initially proposed by de Gennes.
• An inner part of the central region, dominated by loops, shows a mean-field power-law coefficient of -2.
• An outer part, dominated by tails, exhibits de Gennes scaling (-4/3), with longer tails showing enhanced fluctuations near an escape transition.

Conclusions:

• The central region of homopolymer adsorption profiles is more intricate, with distinct inner (loop-dominated) and outer (tail-dominated) parts.
• The -2 scaling in the inner region is a mean-field result, while the -4/3 scaling in the outer region is influenced by tail conformations and fluctuations.
• This refined understanding explains SCF findings and advances polymer adsorption theory.