We study the driven flow of an unentangled glassy polymer film with a free upper surface and supported below by a substrate using nonequilibrium molecular dynamics simulations based on a bead-spring model. Above the glass transition temperature Tg, simple Poiseuille laminar flow is observed with the film mobility defined as the flow current density per unit pressure gradient scaling as h3 with the film thickness h. Below Tg, the film mobility becomes independent of h, signifying surface transport. This is in full agreement with recent experiments on the time evolution of capillary waves in polystyrene films supported by silica. A mobile layer is found responsible for the surface transport, as previously conjectured. Our result also shows that it has a velocity profile decaying exponentially into the bulk.
|Journal||Physical Review E - Statistical, Nonlinear, and Soft Matter Physics|
|Publication status||Published - 16 Oct 2013|
ASJC Scopus subject areas
- Statistical and Nonlinear Physics
- Statistics and Probability
- Condensed Matter Physics