Dynamical Decomposition in Model Polymer Nanocomposites under Creep*

While the elastic properties of polymer nanocomposites (PNCs) have been widely studied, the ability of nanoparticles (NPs) to suppress creep in a polymer matrix has received comparatively less attention. The presence of a slow dynamic layer near the NPs’ surface is widely believed to be the primary mechanism of NP reinforcement. Thus, understanding how the interfacial dynamics, structures, and creep responses change as a function of stress, NP size, and polymer-NP interactions is critical. Here, by introducing a ratio of the interfacial dynamics to the bulk dynamics, we decomposed dynamics in PNCs into two parts: one is structure-dependent and the other is structure-independent. We prove that our decomposition can be further expanded to PNCs under creep, at least within the linear response region. Also, with this decomposition, particles’ free energy barrier for rearrangement can be described as a combination of a packing-related barrier and a packing-unrelated barrier. Our results indicate that both barriers are higher near NPs and decrease with increasing stress, while the packing-independent energy barrier is larger. We also used this model to predict strain-time curves for PNCs under creep, which agree well with the original simulations.