Effects of Heterogeneous Segmental Friction on the Multi-Scale Dynamics of Polymer Nanocomposites

The multi-scale dynamics of polymers at hard material interfaces are highly sensitive to the chemical composition of the components, but this effect remains poorly understood because chemistry dictates not only polymer-interface interaction strengths, but also morphology, polymer flexibility, etc. This work aims to elucidate the effect of polymer-filler interactions on the segmental and chain dynamics of polymer nanocomposites in a simple model system. Here, heterogeneity in segmental friction and chemical composition is introduced by using an unentangled model random copolymer of styrene and 2-vinyl pyridine (2VP), loaded with octa(aminophenyl) silsesquioxane (OAPS) fillers, which interact weakly with styrene monomers, but strongly with 2VP monomers by hydrogen bonding. The neat copolymer dynamics are independent of 2VP mole fraction in the copolymer. The segmental dynamics of these composites are studied by dielectric loss spectroscopy and differential scanning calorimetry, while the chain dynamics are studied by rheology. We observe that changes in segmental dynamics cannot fully explain the slow-down of chain dynamics. The effect of 2VP content in the copolymer on the multi-scale dynamics of the system will be discussed in this presentation.