Suppressing the Rebound of Impacting Droplets from Solvophobic Surfaces by Polymer Additives: Polymer Adsorption and Molecular Mechanisms

TL;DR

This study uses simulations to uncover how polymer additives suppress droplet rebound on solvophobic surfaces by mechanisms involving surface adsorption and molecular retraction forces, advancing understanding of wetting behavior.

Contribution

It provides the first microscopic explanation of how polymer additives prevent droplet rebound, identifying key mechanisms and influencing factors.

Findings

Two anti-rebound mechanisms: slow-retraction and slow-hopping.

Polymer adsorption mediates solvent-surface interactions.

Polymer molecular weight and concentration affect rebound suppression.

Abstract

A liquid droplet impacting on a solvophobic surface normally rebounds. The rebound is suppressed by a small amount of dissolved polymer. In this work, using multi-body dissipative particle dynamics simulations, two anti-rebound mechanisms, the slow-retraction and the slow-hopping mechanisms, are identified. Which of them dominates depends on the polymer-surface attraction strength. However, these two mechanisms are not excluding each other but may coexist. During the droplet rebound, the surface-adsorbed polymer acts in two ways: the adsorbed beads mediate solvent-surface interactions, and highly stretching unadsorbed polymer segment exerts a retraction force on the liquid. Both actions increase the friction against retraction and the resistance against hopping. We also investigate the effects of the molecular weight and the concentration of the polymer additive, the droplet size, and the impact velocity on the rebound tendency. As the first work to provide a microscopic explanation of the anti-rebound mechanism by polymer additives, this study allows better understanding of wetting behavior by polymer-solution droplets.