Ordered solids formed by solvent evaporation

By evaporating the solvent from a colloidal suspension, several types of structures can result. In many cases, you just get a disordered aggregate, but when the process is optimized, very interesting (and useful) structures can arise by self-assembly. We are particularly interested in self-assembly taking place via a liquid crystalline state, the key challenge often being not to loose it as the last solvent evaporates. The situation is complicated by competing evaporation-induced aggregation processes, such as Marangoni flow or the so-called coffee-stain effect, presenting some quite fascinating soft matter physics problems. A promising approach to retain an ordered state that forms early on during evaporation is to take advantage of a jamming transition, which traps whatever state is present at the transition. This is something we explore in our research on suspensions of cellulose nanocrystals, from which photonic crystal films can be produced by water evaporation if the parameters are chosen wisely.


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