Origin of Dynamical Properties in PMMA−C₆₀Nanocomposites

Poly(methyl methacrylate) (PMMA)−C60 nanocomposites, with compositions in the range 0 ≤ φC60wt ≤ 0.05, are shown to exhibit systematic increases in dynamic shear moduli, in glass transition temperature (Tg), and in the longest relaxation time of the polymer (τR) with increasing fullerene concentration. We show that while the φC60wt dependence of the plateau modulus can be reconciled with a conventional “filler” effect, the systematic increases in Tg and in τR are associated with specific interactions between the C60 and the polymer segments. In the melt, these segment−C60 interactions are proposed to reduce polymer segmental mobility in the vicinity of the particle surface and ultimately suppress polymer dynamics, as measured mechanically, in a manner consistent with an increase in the polymer segmental friction coefficient.