The proposal is part of an EPSRC funded programme (EP/GR065705) on surfactant multilayer structures, and involves the interaction between ionic surfactants and oligoions. It complements a previous study of the surface properties of oligo-arene sulfonates with a cationic surfactant, which enable the role of charge spacing and rigidity to be explored. We request beam time on SANS2D to explore and characterise the structure of the solution aggregates, which transform from micelles to complex coacervate droplets. This is essential for our understanding of the surface behaviour in such mixtures.