Crystallization of Polyelectrolyte-Surfactant Complexes at the Air-Water Interface

A system consisting of a strong polyelectrolyte (poly-allyldimethylchloride) and surfactant (sodium-dodecyl-phosphate) is studied by surface synchrotron x-ray techniques combined with surface-tension measurements. It is found that distinct phases are formed at the gas-water interface in regimes where no order is present in bulk. In particular, we find that the addition of salt (NaCl) to a very dilute surfactant in polyelectrolyte solution induces a crystallization of cylindrical micelles with distorted-hexagonal symmetry.