Structure and Dynamics of Hyperbranched Polymer/Layered Silicate Nanocomposites

The structure and dynamics of a hyperbranched polyesteramide (Hybrane S 1200) polymer and its nanocomposites with natural montmorillonite (Na+-MMT) are investigated to offer a detailed picture of its behavior in bulk and under confinement. In bulk, the behavior is probed by quasi-elastic neutron scattering (QENS) with molecular dynamics simulations employed for a better insight into the relevant relaxation processes. The energy resolved elastically scattered intensity from the polymer exhibits two distinct relaxation steps, one attributed to sub-T-g motions and one observed at temperatures above the glass transition, T-g. The QENS spectra measured over the complete temperature range are consistent with the elastic measurements and can be correlated to the results emerging from the detailed description afforded by the atomistic simulations, which cover a broad time range and predict the existence of three relaxation processes. The nanocomposites are investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and QENS. XRD reveals an intercalated nanocomposite structure with the polymer chains residing within the galleries of the Na+-MMT. The polymer chains confined within the galleries show similarities in the behavior with that of the polymer in the bulk for temperatures below the bulk polymer T-g, whereas they exhibit frozen dynamics under confinement at temperatures higher than that.