Introduction

Since the evolution of life began, nature has utilized amphiphilic molecules to form self-organizing structures possessing oil-like interiors and large interfacial areas. Such amphiphilic molecules self-assemble in water to form a variety of microstructures including micelles, vesicles, liposomes, microtubules and bilayers. Phospholipid bilayers act as controlled-access barriers isolating each cell from its environment. Through subtle changes in pH, temperature, ionic strength and counterion, living systems are able to transform continuously from one microstructure to another in response to physiological need. Examples are pinocytosis, endocytosis and phagocytosis. Such transformations guide virtually all biological processes.

Man's exploration of amphiphilic systems as cleaning agents and as decorative and protective coatings dates back to the earliest development of technology. Their utilization in ‘high tech’ applications, such as vesicular carriers for controlled drug delivery or as microdomains for controlled synthesis, depends upon the ability to set amphiphilic structure, maintain its integrity under adverse conditions and then transform it at the end of the process.

An understanding of biological processes at a level of sophistication that goes beyond stoichiometric biochemistry and the ability to utilize amphiphilic microstructures in practical applications requires an understanding of the intricate interactions between water and amphiphilic molecules. This is a complex issue. Self-assembly is a facile physicochemical process in which amphiphilic molecules are physically, not chemically, associated. Their microstructures can transform in response to small perturbations in their environment. In aqueous solutions these processes perturb water in ways that make it difficult to disentangle cause and effect.