3.4. Conductivity Measurement

Critical micelle concentration (CMC) values were obtained conductometrically by using a Conductivty Meter Elmetron CC-505 (Zabrze, Poland). The apparatus was calibrated by using a standard (147 µS/cm in 298.15 K). All the solutions were prepared using double-distilled water. Conductivity measurements were carried out at a temperature of 298.15 K. The conductometric titration was repeated at least three times for each gemini surfactant, and CMC was calculated as the mean value of three measurements.

The CMCs of synthesised 3-oxa-1,5-pentane-bis(N-alkyl-N,N-dimethylammonium bromides) were obtained by conductometric titration, creating relationship graphs of the characteristic conductivity in water of the GS as a function of the concentration [1,63,69,126]. The graphs consist of two lines with differing slopes. The line with higher inclination shows behavior before micellization, and the second line illustrates the process of micellization. The CMC values are at the intersection of the linear regressions of these lines. The degree of counterion binding (β) was calculated according to Frahm’s method [80] as (1 − α), where α = S_micellar/S_premicellar, i.e., the ratio of the slope after and before CMC. The ΔG⁰_mic values were calculated by using Equation (1) [48,127]:

where R is the gas constant, T is the temperature in K, and the CMC is in mol/L.