Molecular dynamics simulation of the capillary leveling of viscoelastic polymer films

TL;DR

This study uses molecular dynamics simulations to analyze the capillary leveling of viscoelastic polymer films, revealing time-dependent viscosity and insights into the polymer's viscoelastic behavior beyond traditional experimental methods.

Contribution

It introduces a molecular dynamics approach to study capillary leveling in viscoelastic polymers, highlighting the time-dependent viscosity and internal mechanisms.

Findings

Viscosity is time-dependent during leveling.

Simulations reveal viscoelastic behavior beyond simple viscosity.

Provides molecular-level insights into polymer surface relaxation.

Abstract

Surface tension-driven flow techniques have recently emerged as an efficient means of shedding light into the rheology of thin polymer films. Motivated by experimental and theoretical approaches in films bearing a varying surface topography, we present results on the capillary relaxation of a square pattern at the free surface of a viscoelastic polymer film, using molecular dynamics simulations of a coarse-grained polymer model. Height profiles are monitored as a function of time after heating the system above its glass-transition temperature and their time dependence is fitted to the theory of capillary leveling. Results show that the viscosity is not constant, but time dependent. In addition to providing a complementary insight about the local inner mechanisms, our simulations of the capillary-leveling process therefore probe the viscoelasticity of the polymer and not only its viscosity, in contrast to previous experimental approaches.