How do the novel substituted 3H-indole probe molecules reside in the AOT-based water-in-oil microemulsion?

A surface-active substituted 3H-indole quaternary ammonium molecule, [2-(p-cetylaminophenyl)-3,3-dimethyl-5-ethoxycarbonyl-3H-indole] methyl dihexadecyl-ammonium iodide (3), was designed and synthesized in hexamethyl phosphoramide (HMPA). The product was purified and characterized by IR, 1H NMR, MS and elemental analysis. Using 3 and its homologue [2-(p-dodecylaminophenyl)-3,3-dimethyl-5-ethoxycarbonyl-3H-indole] methyldihexadecyl ammonium iodide (2), we have measured the protonic association constant, the fluorescence anisotropy for the two molecules in the AOT-based water-in-oil (w/o) microemulsion, as well as the dielectric constant of the microemulsion interface sensed by 2 and 3. The results provide further evidences supporting our previous viewpoint about the locations of different groups of this kind of substituted 3H-indoles in the microemulsion.