Influence of chain interdiffusion between immiscible polymers on dewetting dynamics

From dewetting and neutron reflectivity experiments, we demonstrate the major influence of chain interdiffusion on the friction properties for a couple of immiscible polymers. The interface between two immiscible polymers, polystyrene (PS) and polydimethylsiloxane (PDMS), was studied by neutron reflectivity and dewetting by using free PS chains and PDMS brushes. Unexpectedly, we found that the PS chains diffuse in the PDMS brushes at temperatures well below the glass transition temperatures of PS, the dynamics being largely determined by the grafting density of the brush. These observations strongly suggest that the puzzling ageing of PS thin films observed from dewetting experiments can be directly related to modifications of the PS/PDMS interface.