Measuring the Surface Dynamics of Glassy Polymers
Original entry: Ian Burgess, Fall 2009
Polymer chain segments in bulk polystyrene cooled below the glass transition temperature experience little to no mobility, however this is not necessarily true at the polymer surface. The authors in this study measure the mobility of polymer chains near the surface of a film below the glass transition temperature. By partially embedding gold nanospheres at the surface and then removing them, leaving behind dimple-like impressions in the film, they observe the motion of polymer chains near the surface via the relaxation of the surface deformation. A fundamental challenge of this type of experiment is that the surface deformation must be produced without inducing any stress in the film, as stress would also induce such a relaxation without requiring any fluid-like mobility in the chains.