Intermixing between chemically different polymers around nanoparticles creates chemically heterogeneous layers, exhibiting unusual dynamic anomalies due to dynamic confinement and coupling phenomena in polymer nanocomposites. Interfacial mixing of chains is possible when adsorbed chains are mobile above their glass-transition temperature, leading to enhanced entanglement density at the interphase. Linear rheology data of polymer nanocomposites with chemically heterogeneous interphases around nanoparticles were analyzed over a wide frequency range to investigate the role of chain rigidity on matrix chain relaxations and particle diffusion. Our findings show that nanoparticles adsorbed with less rigid polymer move in a sub-diffusive mode. Nanoparticles adsorbed by flexible polymers can slow down the matrix polymer dynamics and particle diffusion, and this interphase effect enhances the viscoelastic properties of the whole polymer nanocomposite.

Thermally activated shear stiffening viscoelastic fluid can help to improve the performance of viscoelastic dampers and high-temperature adhesives. Polymer nanocomposites with heterogeneous interphases are applied to design such adaptive materials. In this work, shear stiffening in polymer-grafted nanoparticle composites is investigated. We report the linear rheological responses of grafted particle composites before and after large-amplitude oscillatory shear application. We found that interfacial mixing of short grafts with chemically different long matrix chains led to the enhancement of plateau moduli and terminal relaxations, unlike with the long grafts. Moreover, we showed that the elastic modulus of grafted chains was enhanced upon deformation through inter-diffusion and entanglements of interfacial layers with the short matrix chains in both grafted systems. These results suggest that dynamic coupling between chemically different polymers away from nanoparticle surfaces is a design strategy to achieve the thermally stiffening behavior in polymer nanocomposites.

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The use of ionic liquids as solvent for polymers or polymer-grafted nanoparticles provides an exciting feature to explore electrolyte-polymer interaction. 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIm-TFSI) holds specific interactions with the polymer through...

The entanglements of dynamically asymmetric polymer layers influence relaxations of nanoparticles in polymer nanocomposites. In this work, dynamics of polymer-adsorbed and polymer-grafted nanoparticles in poly(methyl acrylate) matrix polymer was investigated...