2.2.3. Time-Resolved Surface Potential Experiments

We measured the surface potential as a function of time by means of a Kelvin probe (KSV-NIMA SPOT). The experiment is schematized in Figure 2 and it is as follows: A concentrated solution of G12-2-12 (surfactant concentration, *c*<sup>s</sup> = 0.1 M), is prepared and let stabilize for 24 h. Separately, a precisely measured volume of pure water (Milli-Q) is placed in a small Teflon cuvette. The surface potential probe is placed at about 2 mm above the water surface. The surface potential of pure water is then measured and the result saved. By means of a Hamilton syringe (50 μL), a certain volume of the concentrated Gemini solution, calculated in order to obtain the desired final concentration, is injected at the bottom of the Teflon cuvette, producing a concentration impulse while the surface potential is continuously monitored. The injection process takes about 5 s. The injection process must be done very carefully, the syringe needle must be perfectly cleaned and any movement that could produce convection must be avoided. For changing the final surfactant concentration, we changed either the initial volume of water or the volume of the surfactant solution injected.

**Figure 2.** Scheme of the time-resolved surface potential experiment.

#### **3. Results**
