Physical science of the didodecyldimethylammonium bromide-water system: 1. Equilibrium phase behaviour.

Surfactant molecules in solvents self-assemble into a large variety of structures depending on their chemical composition, concentration and temperature, summarized in the system's equilibrium phase diagram. However, the occurrence of long-lived metastable states can lead to incomplete or partly incorrect phase diagrams. By applying a set of complementary techniques and recording changes on different length scales, we determine an improved aqueous equilibrium phase diagram of the widely used double-chain surfactant didodecyldimethylammonium bromide (DDAB) over a broad concentration range ( = 3-100 wt%).