Hierarchical Self-assembly, Spongy Architecture and Phase States of Laponite in low polar solvents*

We propose an alternative method to tune the electrostatic interactions to obtain a transition from a repulsive to an attractive system of nanoplatelets by increasing the alcohol concentration, i.e. increasing the Bjerrum length. A phase diagram of Laponite^® in alcohol solutions has been proposed, which clearly demarcates regions of stable sol, unstable sol, transparent gel, turbid gel, glass, and flocculation. A new class of soft materials, called nanoclay-organogels, was deeply explored using confocal and scanning electron microscopy that depicted spongy architecture and presence of nano and micron size pores inside the gel matrix indicating the hierarchical self-assembly of the nanoplatelets in the binary solvent. Universal power-law scaling of storage modulus and yield stress with alcohol concentration was observed. We have extensively examined the dispersion stability, aggregation and gelation behaviour of Laponite nanoplatelets in different alcohol -water binary solvents, thereby proposing a universal description of nanoclay dispersion in alcoholic solutions, which is poorly probed and marginally understood in the literature.