ABSTRACT
I fo r my part have never known an Irregular who was not also what Nature evidently intended him to be-. . . up to the limits o f his power, a perpetrator o f all manner o f mischief.
From A bbott’s Flatland
8.1a What Is Self-assembly and What Are Association Colloids? In the last chapter we examined the tendency of surfactant molecules in aqueous solutions to adsorb at a surface in the form of a monolayer. In this chapter we continue to study surfactant solutions, this time considering a few of the many possible modes of organization they can adopt within a bulk phase. This process of organization is thermodynamically driven and is spontaneous, as in the case of Langmuir layers we discussed in Chapter 7. It is therefore often called self-assembly, and the resulting aggregates are known as association colloids. Both chapters share an interest in amphipathic solutes: Chapter 7 focuses on surface activity, while this chapter is concerned with structures in the colloidal size range formed by these molecules. In both, the head-to-head/tail-to-tail ordering of the amphipathic molecules is observed. The difference is that in Chapter 7 the ordering occurs at the surface, under the influence of the surface, while it occurs in the bulk in this chapter. Quite an assortment of bulk surfactant structures is known, including ordinary and reverse micelles, liquid crystals, bilayers, vesicles, and microemulsions. This chapter is concerned primarily with micelles (Sections 8.2-8 .8) and microemulsions (Sections 8.9 and 8.10), although some additional structures are mentioned in passing.
