Wetting transitions of polymer solutions: Effects of chain length and chain stiffness

TL;DR

This study investigates how chain length and stiffness influence wetting transitions in polymer solutions using simulations and theoretical calculations, revealing complex dependencies on polymer properties.

Contribution

It introduces a combined simulation and density functional theory approach to analyze wetting transitions considering chain length and stiffness effects.

Findings

Wetting transition temperature increases with chain length for flexible polymers.

For semiflexible polymers, the transition temperature varies non-monotonically with stiffness.

A sudden drop in transition temperature correlates with isotropic-nematic phase transition.

Abstract

Wetting and drying phenomena are studied for flexible and semiflexible polymer solutions via coarse-grained molecular dynamics simulations and density functional theory calculations. The study is based on the use of Young's equation for the contact angle, determining all relevant surface tensions from the anisotropy of the pressure tensor. The solvent quality (or effective temperature, equivalently) is varied systematically, while all other interactions remain unaltered. For flexible polymers, the wetting transition temperature $T_{\rm w}$ increases monotonically with chain length $N$, while the contact angle at temperatures far below $T_{\rm w}$ is independent of $N$. For semiflexible polymer solutions, $T_{\rm w}$ varies non-monotonically with the persistence length: Initially, $T_{\rm w}$ increases with increasing chain stiffness and reaches a maximum, but then a sudden drop of $T_{\rm w}$ is observed, which is associated with the isotropic-nematic transition of the system.