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

Abstract

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 quasielastic 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.

Heterogeneous Glass Transition Behavior of Poly(Ethylene oxide)/Silica Nanocomposites via Atomistic MD Simulations

“…This behavior implies that dynamic heterogeneities tend to disappear upon heating the system well above its T g . This trend lies in accordance with findings from other experimental and simulation studies in thin polymer films and binary Lennard-Jones liquids. − …”