The dynamics of polymer nanocomposites (PNCs) are dictated by two intertwining components, the polymer matrix and the nanoparticle network, whose characteristics have not been elucidated. Here, we unravel the salient features of the polymer matrix dynamics and the nanoparticle network dynamics through dielectric spectroscopy and rheology. Dielectric measurements show that the dynamics of the polymer matrix of PNCs are almost identical to that of the neat polymer. In contrast, rheological measurements exhibit a strong deviation in the dynamics of PNCs from that of the neat polymer. Detailed analyses show that the rheology captures both contributions of the polymer matrix and the nanoparticle network while dielectric measurements are only sensitive to polymer matrix dynamics. Moreover, the dynamics of the polymer matrix and the nanoparticle network have very different temperature dependences, leading to a dynamic decoupling phenomenon and the breakdown of the time–temperature superposition principle in PNCs.

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This Letter investigates the external deformation on modifying the polymer−nanoparticle (NP) and NP−NP interactions as well as their influences on the macroscopic properties of polymer nanocomposites (PNCs). Specifically, the applied uniaxial extension brings together the NPs along the transverse stretching direction and catalyzes the percolation transition from the initially well-dispersed NPs in the PNCs. The percolated NP network thus increases the strength of PNCs and leads to a strong surge in the elongation viscosity at very low strain rates, exhibiting the unexpected nonmonotonic strain rate dependence on the strain hardening. These results reveal explicitly the unconventional roles of the external deformation on modulating the relative strength of the polymer−NP and the NP−NP interactions, enabling advanced structures and properties control of PNCs.

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