Controlling Microphase Separation In Graphene Dispersions - Diffusion-Limited Aggregation to MesoCrystallization

Advances in polymerized ionic liquids (PIL) have made it feasible to prepare thermodynamically stable dispersions of nanocarbons (SWCNT, MWCNT, graphene) by top-down liquid phase exfoliation processes. A versatile stimuli-responsiveness of some PIL makes it possible to destabilize such dispersions to create interesting materials from fast destabilization in the diffusion-limited aggregation limit to formation of mesocrystals on conformal substrates. We illustrate introductory examples for the case of concentrated aqueous graphene dispersions where destabilization is controlled by varying the ionic solvent components in water that modulate the solvation of the PIL ionic sites. These phenomena can be understood in terms of reversible (pinned) spinodal decompositions exhibited by such PIL in binary solvent systems. Collateral phenomena, including reversible poration, multi-time scale micro-phase separations, isotropic-to-nematic transitions, and rheo-optical effects are also illustrated.