Designing Polymer Nanocomposites: Critical Role of the Interfacial Layer

It is now well recognized that interfacial layer controls macroscopic properties in polymer nanocomposites (PNCs). In this talk we overview recent studies on structure and dynamics of the interfacial layer in various PNCs. We employ broad array of experimental techniques and MD-simulations that provide detailed characterization of the interfacial layer. These studies revealed a gradient in the interfacial layer dynamics, but no “glassy” or “dead“ layer. The thickness of the interfacial layer increases upon cooling to Tg, and depends strongly on polymer rigidity, increasing from ~2nm in flexible polymers to ~5 nm in more rigid ones. We discuss a possible connection of the interfacial layer thickness to the dynamic heterogeneity length scale. We emphasize usually overlooked dynamic property of the interfacial layer – strong suppression of the amplitude of structural relaxation on time scale of segmental dynamics. At the end, we present a general picture how microscopic parameters control the interfacial layer, and how by tuning the interfacial layer we can tune macroscopic properties of polymer nanocomposites.