Incorporating fairly low volume fractions of nanomaterials into polymers creates composites with a vast amount of interfacial area for potential matrix-filler interactions. This surface area provides interfaces between the polymer matrix and the filler at which polymer chains are physically and, potentially, chemically constrained, affecting the local mobility of the polymer chains. In this study, we investigate the properties of this interphase region in several styrene-based polymers and carbon surfaces via model thin film systems. We employ dynamic nanoindentation to probe viscoelastic interphase enhancements in supported thin films for four different polymers with a wide range of glass transition temperatures. The results demonstrate that interphase enhancements depend upon the nature of the substrate/polymer interaction and the average mobility of the polymer, glassy or rubbery. We hypothesize that strongly positive interactions between styrene and graphitic surfaces through pi-pi secondary interactions at the interface create the interphase enhancements we measure and quantify.
Wood, C. D., Chen, L., Burkhart, C., Putz, K. W., Torkelson, J. M., & Brinson, L. C. (2015). Measuring interphase stiffening effects in styrene-based polymeric thin films. Polymer, 75, 161–167. https://doi.org/10.1016/j.polymer.2015.08.033