(797a) Invited Talk: Thermodynamics of Nanoparticle-Polymer Melt Hybrids

While the miscibility and spatial dispersion of nanoparticles (NPs) in a polymer melt critically affects the properties of the resulting nanocomposite, little simulation work exists on understanding this critical issue. We examine a recent experimentally motivated conjecture by Mackay that miscibility between NPs and polymer melts is achieved when the chains are larger than the nanoparticles using isothermal-isobaric ensemble simulations. In the case of systems with attractive interactions we show that polymer chain length only plays a secondary role, probably because the entropic, depletion-induced inter-NP attractions only occur over length scales comparable to the correlation length in the melt, namely the segment size. We therefore consider athermal systems and show indeed that there is a fascinating role played by polymer chain length relative to the NP size in determining "miscibility" and NP self-assembly. The consequences of these results on experimental results will be the final piece of this story that we shall discuss.