  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.
