(721d) Influence of Strucure and Dynamics in Matrix-Free Polymer-Grafted Nanocomposite Memebranes

Recent works have exhibited enhanced molecular transport for membranes comprised solely of polymer grafted nanoparticles compared to that of bulk polymer or un-grafted, “traditional” mixed composites. Additionally, these enhancements appear non-monotonic as a function of grafted chain length. We postulate chemically grafting polymers to the surface of nanoparticles restricts the ability of the chains to sufficiently pack the spaces between the particle cores. In this regime, there exist locations which are essentially “starved” of polymer at the edges of the brush. To support these claims and investigate the origin of the non-monotonic behavior in diffusion we use both linear and non-linear rheology to probe the chain dynamics. In addition, small angle X-ray and contrast variation small angle neutron scattering (SAXS, SANS) are employed to investigate how structure may influence the unexpected performance of these membranes. The elucidation of the mechanism behind this phenomenon may lead to simple rational design of high performance membrane technology for gas purification.