Evidence of re-entrant behavior in laponite-PEO systems

Rheology and dynamic light scattering capture re-entrant behavior of laponite-polymer systems. Neat laponite under basics conditions and concentrations of 2wt% or greater forms a viscoelastic soft glass due to electrostatic repulsions. We show that that addition of low molecular weight poly(ethylene oxide) (PEO) melts the glass due to a depletion force. The depletion force speeds up dynamics in the system resulting in a low viscosity solution. A reentrant viscoelastic solid is formed with the addition of high molecular weight PEO due to the polymer chains bridging between laponite particles. As expected the transition from a low to high viscosity solution scales with the polymer mean square end-to-end distance and gap between laponite particles.