Microrheological characterisation of clay-PEO nanocomposites

Clay-polymer mixtures, characterised by high mechanical stiffness, are widely utilised in strengthening soft and easy-to-break materials. Here, we present microrheological results on shake-gels made of natural (montmorillonite) and synthetic (Laponite) disk-shaped clay particles in combination with poly(ethyleneoxide). These clay-polymer suspensions represent shear-thickening fluids that display a large increase in viscosity upon large-amplitude shaking. By performing both bulk and microrheology experiments, we probe the phase behaviour and mechanical response of these nanocomposites. Slight tuning of either the particle or polymer concentration leads to dramatic changes in the macroscopic appearance of the mixture, transitioning from a low-viscosity fluid to a stiff gel, capable of sustaining its own weight. We relate these observations to microscopic measurements, providing insight into the local reorganisation of the constituting building blocks and the time-evolution of each phase.