Ringing gels: Their structure and macroscopic properties

The phase diagram of the ternary surfactant system which consists of dimethyltetradecylaminoxide, hydrocarbon, and water contains a highly elastic gel phase which borders on the micellarL ₁-phase. This gel phase is transparent, optically isotropic, and shows the ringing phenomena when it is excited to mechanical vibrations. From SANS and light-scattering measurements it is shown that this phase consists of the same spherical microemulsion droplets which are present in the adjacent micellar solution. Even in the micellar solution the droplets are fairly monodisperse and in the SANS scattering functions a second scattering maximum was observed. Both the light scattering and SANS data can be described quantitatively on the basis of hard sphere interactions between the particles. Furthermore, it is shown that elasticity and shear modulus of the gel phase, which were determined experimentally, correlate with the compressibility modulus as calculated from the scattering data. The elasticity modulus and hence the osmotic compressibility modulus are related to the Laplace pressure inside the globules. For the calculation of this pressure it is possible to take the interfacial tension, which is obtained from a dilute micellar solution against the hydrocarbon which is used for the system. The radius of the particles and the hydrocarbon content in the system can be increased when some of the dimethyltetradecylaminoxide is replaced by dimethyltetradecylphosphinoxide.