Catanionic bilayers as micro-crystals with in-plane ordered alternated charges

Recent progresses in the understanding of properties of catanionic surfactant aggregates are reviewed. These aggregates are charged microcrystals produced upon co-crystallisation of anionic and cationic surfactants without excess salt. They were studied applying methods developed for polyelectrolyte multilayered capsules. They have been observed without special preparation by soft X-ray microscopy. Confocal optical microscopy allowed first measurements of the diameter of the holes present at vertices. These observations could be rationalized by identifying the formation path in the phase prism. Rigidity was measured directly using the colloidal probe method and calculated using mesoscopic modelling. These progresses made within of the French-German network are discussed versus recent results obtained by other groups working on catanionics. (c) 2007 Elsevier B.V. All rights reserved.