Understanding thermo-responsive re-entrant phase behavior in nanoparticle-pluronic system.

The delicate interplay of different interactions in colloids gives rise to interesting re-entrant phase behavior, where the system undergoes a phase change and return to original phase with respect to a monotonic variation in a specific physicochemical parameter. The emergence of such phase transitions are usually beyond the generalized understanding of colloidal science and requires involvement of complex multi-body interactions. We have observed re-entrant liquid-liquid phase separation in silica nanoparticles-pluronic (triblock copolymer) suspension, where the system transforms from stable one-phase to two-phase (aggregate) and then return back to original phase on increasing temperature. The observed phase transition is reversible as well as thermo-responsive in nature, associated with lower consolute temperatures. We propose to carry out SANS measurements to study the evolution of structure and interactions, for determining the origin of such phase behaviour.