Colloid Chemistry: The Fascinating World of Microscopic Order

Abstract

In this work, we explain how small surfactant molecules with dimensions of one to two nanometers,when dissolved in water with a concentration of a few weight percent, organize themselves spontaneouslyinto various structures with a long-range order over macroscopic dimensions of several centimeters,even though the molecules are all in the liquid state. It follows that two molecules that are more thana million times their main length apart still point, on average, in the same direction in three dimensionalspace.

The organized structures give to the aqueous phases new macroscopic properties like iridescent colors,viscoelasticity, gel character, a yield stress, and, between crossed polarizers, beautifully coloredpatterns that make the order in the samples visible. The self-organization of the surfactant moleculesis simply a result of the hydrophobic and electrostatic interaction between the individual moleculesand the micellar structures. The size of the micellar structures, as in the case of small unilamellar vesicles,can be extremely monodisperse, even though one vesicle consists of hundreds of surfactant molecules.