Studies of cationic and nonionic surfactant mixed microemulsions by small-angle neutron scattering and pulsed field gradient NMR

For mixed surfactant films in water-in-oil microemulsions, insight into the interfacial structures and compositions has been obtained by combining data from pulsed field gradient NMR (PFG-NMR) and small-angle neutron scattering (SANS). As an example of this approach we report a preliminary study on water in n-heptane microemulsions stabilised by mixtures of didodecyldimethylammonium bromide and pentaethylene glycol monododecyl ether. The results deduced from both methods are consistent with spherical microemulsion droplets stabilised by a mixed surfactant film. It is shown that the combination of SANS and PFG-NMR is extremely powerful for investigating these multi-component systems. In particular, dynamic studies by PFG-NMR are useful for validating models for SANS data.