  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.
