Correlation between backbone and pyridine dynamics in poly(2‐vinyl pyridine)/silica polymer nanocomposites

Polymer segmental dynamics in polymer nanocomposites (PNCs) can be significantly perturbed from bulk and underlie macroscopic mechanical and transport properties, but fundamental studies are necessary to build correlations between dynamics and properties. To elucidate a mechanistic description of this perturbation and isolate different molecular motions, we present quasi‐elastic neutron scattering (QENS) measurements on PNCs with attractive interactions comprised of colloidal silica nanoparticles (NPs) uniformly dispersed in poly(2‐vinyl pyridine) (P2VP) with and without backbone deuteration. Measurements of fully‐protonated P2VP probe the dynamics of both the polymer backbone and pyridine pendant group; whereas measurements of backbone‐deuterated P2VP isolate the dynamics of only the pyridine ring. On the small length scales (~1 nm) and fast time scales (~1 ns) captured by QENS, we show that the backbone and pyridine ring dynamics are highly coupled at high temperatures and both are slowed by about 35% relative to neat polymer in 25 vol% PNCs. This observation implies that the backbone and pendant interfacial dynamics are perturbed similarly in PNCs, which further develops our fundamental understanding of microscopic properties in PNCs. This study presents quasi‐elastic neutron scattering measurements to isolate the dynamics of pendent groups and chain backbones in model polymer nanocomposites with attractive interactions. It is found that the pendant group is slightly more mobile than the backbone in neat polymer and nanocomposites. Although both molecular motions are temporally slowed by the presence of nanoparticles, their motions are highly coupled. This work provides unique mechanistic insight into the perturbation of nanoparticles to molecular motions in polymer nanocomposites.