Deforming Interfacial Layers of Bare and Grafted Particle Nanocomposites in Large Amplitude Oscillatory Shear

Chemical heterogeneity around nanoparticles yields enhancement in mechanical properties in polymer nanocomposites. We have shown interfacial layers composed of two miscible polymers on well-dispersed nanoparticles control the dynamics of chains and their temperature-induced stiffening response. In this work, we examined these interfacial layers and the evolution of entanglements under large amplitude oscillatory shear to reveal the stability of mechanical and structural behavior of attractive composites. Deformation-recovery experiments have shown that particles adsorbed with low rigidity polymer (PMMA) disentangle/re-entangle and reinforcement factor increased significantly, whereas with the high rigidity polymer (P2VP) the modulus recovered to its initial value. Fourier transform rheology results indicated that strain-softening resulted from the arrangement of interfacial PMMA chains, which yielded to a higher entanglement state and stiffening. The non-linear rheology results of the PMMA-grafted particles will be discussed with the results of PMMA-, PC- and P2VP-adsorbed chains with varying rigidity. Large shear-induced entanglements can therefore be explained through the deformability of chains in interfacial layers.