Macroscopic dynamics of polystyrene grafted silica nanoparticles in a homopolymer matrix

Silica nanoparticles grafted with polymers, dispersed in a homopolymer matrix, and annealed over time adopt a broad range of dispersion states which depend on grafting density, annealing time, weight percent silica, and the molecular weights of the polymers.~ We tuned these variables to give desired dispersion states, from uniformly dispersed particles to agglomerated clusters.~ Rheology was used to critically determine how the dispersion state affects the mechanical reinforcement of the composite.~ We have run both steady shear and small amplitude oscillatory shear experiments on nanocomposites comprising a range of dispersion states. By mapping the observed reinforcement on a morphology diagram, we observe the location of a maximum in reinforcement.