(751g) Molecular Simulation Studies of Polydispersity Effects On The Morphology of Polymer Nanocomposites

In this talk we will present molecular simulation studies elucidating polydispersity effects in polymer grafted nanoparticle based polymer nanocomposites. Past literature has shown that, in polymer nanocomposites containing monodisperse polymer (brush) grafted particles in a monodisperse polymer matrix, when the graft and matrix polymers are chemically similar, the grafted particles are dispersed (aggregated) in the polymer matrix when the grafted polymer chains are much longer (shorter) than the matrix polymer chains. We have shown in recent work [1,2] that polydisperse grafted polymers can stabilize dispersions of polymer grafted nanoparticles in a polymer matrix even if the average grafted polymer chain length is less than the matrix chain length. This is because the polydispersity in grafted polymers relieves monomer crowding in the grafted polymer layer on the particle, and improves wetting of the grafted layer by the matrix chains. In this talk, we will present our recent work extending the understanding of polydispersity effects in nanocomposite by focusing on polydispersity in matrix chains. In the case of a bidisperse matrix, consisting of short and long chains, with monodisperse polymer grafted particles, we find that the grafted polymer layer is preferentially wet by the short matrix chains, even when the short matrix chains are longer or higher in molecular weight than the graft polymer chains. These results suggest that polydispersity can be a useful design parameter to improve filler dispersion in polymer nanocomposites.

[1] Martin, T. B.; Dodd, P. M.; Jayaraman, A.; Polydispersity for Tuning the Potential of Mean Force between Polymer Grafted Nanoparticles in a Polymer Matrix. Phys. Rev. Lett. 2013, 110 (1), 018301.

[2] Martin, T. B.; Jayaraman, A.; Polydisperse homopolymer grafts stabilize dispersions of nanoparticles in a chemically identical homopolymer matrix: an integrated theory and simulation study. Soft Matter 2013. DOI: 10.1039/C3SM00144J