Direct Mapping of Nanoscale Viscoelastic Dynamics at Nanofiller/Polymer Interfaces

Abstract

The mobility gradient of polymer chains near a solid interface plays an important role in explaining a complex behavior of relaxation dynamics and thermodynamic properties observed for various polymer nanocomposites. However, it still remains a major challenge to directly visualize this gradient at nanoscale. By means of loss tangent imaging in amplitude-modulated atomic force microscopy, we report a direct mapping of the nanoscale viscoelastic dynamics of interfacial polymers in two model nanocomposites including isoprene and styrene–butadiene rubbers filled with carbon black nanofillers. The loss tangent images clearly show a gradual slowdown of the viscoelastic dynamics of interfacial polymers from the bulk to the glassy behavior of a tightly bound layer over a length scale of ∼30 nm. These results can therefore provide important insights into understanding the long-existing question about the dynamic behavior at the nanofiller/polymer interfaces.