Unfolding of Polymer Thin Films on Liquid Surfaces

Ultrathin polymer films are difficult to handle. Liquid support layers are often used to ease the manipulation of these films. However, removing the film from the liquid support leads to the fluid draining from the interface, and without the liquid, the polymer interface adheres to itself, forming a crumpled film. The polymer thin film will remain crumpled due to the adhesion forces being higher than the cohesion strength of the film. Here, we report a processing method to allow for reversible folding and unfolding of ultrathin polymer films from liquid surfaces. We explain the folding and unfolding mechanism through tuning the surface interactions at the polymer-liquid interface. We demonstrate the ability to fold and unfold several types of polymer thin films on different liquid surfaces.