Suppression of Polymer Degradation in Polymer Infiltrated Nanoparticle Films*

In many industrial applications such as coatings and adhesives polymeric material are processed at high temperatures under conditions where most of the material is within a few nanometers from an interface, sometimes sandwiched between rigid surfaces. Under these conditions, reaction rates and pathways to degradation can be significantly affected, due to multiple factors. Variables such as the rate of oxygen diffusion into the film and product diffusion out, changes in polymer viscosity, interfacial interactions, and changes in the boundary condition from constant pressure to constant volume can affect the rate of degradation. In this study, we use capillary rise infiltration (CaRI) to infiltrated polystyrene in silica nanoparticles with various particle diameters. We show that as the particle diameter is decreased, polymer degradation can be significantly delayed, and the process may change from oxidative decay to pyrolytic degradation, despite heating in ambient conditions. We discuss the origins of this suppression of degradation and possible pathways to further improve polymer stability towards degradation.