Chain dynamics and nanoparticle motion in attractive polymer nanocomposites subjected to large deformations

Abstract

The effect of large deformation on the chain dynamics in attractive polymer nanocomposites was investigated using neutron scattering techniques. Quasi-elastic neutron backscattering measurements reveal a substantial reduction of polymer mobility in the presence of attractive, well-dispersed nanoparticles. In addition, large deformations are observed to cause a further slowing down of the Rouse rates at high particle loadings, where the interparticle spacings are slightly smaller than the chain dimensions, i.e. in the strongly confined state. No noticeable change, however, was observed for a lightly confined system. The reptation tube diameter, measured by neutron spin echo, remained unchanged after shear, suggesting that the level of chain-chain entanglements is not significantly affected. The shear-induced changes in the interparticle bridging reflect the slow nanoparticle motion measured by X-ray photon correlation spectroscopy. These results provide a first step for understanding how large shear can significantly affect the segmental motion in nanocomposites and open up new opportunities for designing mechanically responsive soft materials.

Resolving Segmental Polymer Dynamics in Nanocomposites by Incoherent Neutron Spin–Echo Spectroscopy

“…The collective motions associated with segmental relaxation are probed in fully deuterated (D) samples by NSE (coherent scattering) . NSE also allows us to observe the single-chain dynamic structure factor and the reptation process, using H/D contrast between chains. − However, the use of deuterated chains is hardly feasible for industrial mixing processes, necessitating large quantities. It is shown here for the first time that incoherent NSE obtained with purely hydrogenated samples allows accessing the local segmental dynamics on the scale of approximately a nanometer in polymer nanocomposites, without perturbation by the coherent silica scattering.…”

Deformation of Chemically Heterogeneous Interfacial Layers of Polymer Nanocomposites

“…Attractive interactions between particles and polymer chains control not only the good dispersion state of particles in nanocomposites but also the dynamics of polymer chains on particle surfaces. − Dispersion of fillers, percolation of particles, and bridging between interfacial bound chains are known to control the reinforcement in composites. − In previous works, the dynamics and structural conformations of adsorbed polymer layers are investigated in composites with chemically identical adsorbed and matrix chains. − The chemical heterogeneity in interfacial polymer layers offers intriguing dynamic properties that depend on dynamic confinement and coupling phenomena of polymer blends. − …”

Viscosity reduction in polymer nanocomposites: Insights from dynamic neutron and X‐ray scattering

“…PNCs consisting of silica nanoparticles dispersed in PEO are one of the most commonly investigated model systems. For example, rheological, 88 Nuclear Magnetic Resonance, 89 neutron scattering 15 as well XPCS 90 measurements have been performed on them. Because of the hydrogen bonding forming between the ester group of the monomer and the hydroxyl group on the surface of the untreated nanoparticles the interaction is attractive.…”