Recent advancements in the quality and quantity of nanoparticles have increased their use in polymer nanocomposites. Their small size creates the opportunity for interesting size ratios and limits. One of these, the nanoparticle limit, where the particle is smaller than the suspending polymer radius of gyration, has resulted in surprising effects to the mechanical properties among them a decrease in the melt viscosity and an increased Young's modulus in the solid state. Dispersing nanoparticles within polymers plays a critical role in nanocomposite properties, and the dispersion stability is very sensitive to the confinement limit (h < Rg) and solubility limit (a < Rg). Bimodal blends of linear polystyrene with tightly crosslinked polystyrene nanoparticle having a small volume fraction of unconfined chains or a small volume fraction of chains larger than the nanoparticle fail to show any unique features. Knowing the sensitivity of these limits allows for proper selection of polydisperse nanoparticles and polydisperse linear chains producing a fully polydisperse system with reduced viscosity. Rheology gives a rough estimate of dispersion in a system of tightly crosslinked polystyrene nanoparticles in linear perdeuterated polystyrene via either a viscosity reduction or adherence to Einstein's predicted viscosity increase. Dispersion or agglomeration in these systems is confirmed though small angle neutron scattering and solubility and mixing energies are calculated via Guinier and Virial analysis. These results follow the scaling penalty from chain stretching as nanoparticle radius approaches linear polymer radius of gyration. However, even in the agglomerated case rapid precipitation produced a well dispersed system that phase separated during thermal annealing. Refinements to the rapid precipitation blending technique yielded an ideal polymer concentration for proper blending and subtle difficulties are discussed. Finally the melt viscosity of poly(methyl methacrylate) C60 and poly(methyl methacrylate) Fe3O4 nanocomposites show a reduced viscosity, results which are contrary to recently reported experiments. The method of dispersion is the key difference between this work and what has been reported in the literature. Young's Modulus was also measured with only the poly(methyl methacrylate) Fe3O4 nanocomposite resulting in an increase, indicating a dependence of unusual reinforcement on nanoparticle size and spacing. These details and other phenomena are discussed in this work.
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