Structure and interfacial interactions of thin films of amylopectin

Abstract

Structure and interfacial properties of micrometer-thick amylopectin films were investigated. The polysaccharide amylopectin forms the crystalline regions in native starch. By applying X-ray scattering at wide and small angle detection modes, and surface microscopy (phase interference microscopy and atomic force microscopy), we were able to probe the film structure and the surface morphology. The thin films were found to be amorphous with some degree of orientational order in the direction normal to the surface. A step-like surface morphology was observed, with a typical step-height of 100 nm and lateral dimensions of 100 μm. We investigated the interfacial interaction between amylopectin and polystyrene and found that the stability of polystyrene films on top of the amylopectin substrate depends on film thickness: thin films (adsorbed layers of a few nanometers) were stable due to short-range interactions, while thicker films (of a few hundred nanometers) dewetted due to van der Waals interactions.