Molecular dynamics simulation of the capillary leveling of viscoelastic   polymer films
  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. 
Ioannis Tanis, Hendrik Meyer, Thomas Salez, Elie Rapha\"el, Anthony C.   Maggs, and J\"org Baschnagel
cond-mat.soft cond-mat.mes-hall cond-mat.stat-mech physics.comp-ph physics.flu-dyn