A model nanocomposite designed to understand the interfacial behavior in a novel thermally stiffening nanocomposite*

A novel polymer-adsorbed silica-reinforced nanocomposite with a heterogeneous structure was recently shown to have thermal-stiffening behavior. Although the macroscopic properties of this nanocomposite were characterized via rheological experiments, the structure and dynamics at the matrix-nanofiller interface remain to be investigated. In the current study, we use a simplified 2D system to mimic the complex 3D structure of the nanocomposite. The simplified sandwich structure consists of a flat silica substrate, a thin layer of adsorbed high glass transition temperature polymer (PMMA, P2VP, and PC), and a final layer of PEO. Modulated Differential Scanning Calorimetry (MDSC) and Thermogravimetric Analysis (TGA) experiments indicated that the conformation and the relaxation in the confined environment surrounded by the hydroxyl group-rich silica surface and flexible PEO chains were significantly altered. Besides, by carefully changing the thickness, annealing condition, and molecular weight, different trends were observed which corresponds to different possible mechanisms. The results are of great help in understanding the previous real nanocomposite results and they also provide some strategies to design nanocomposites with desired properties.