Determination of critical micelle concentration

Aqueous solutions of surfactant and co-surfactant with different concentrations but constant concentration of polymer were prepared. Surface tension of these solutions was measured at 25 °C with a Torsion balance (WHITE ELEC Model NO. 83944E). Then, the surface tension versus log concentration was plotted. There is a break in surface tension at a concentration associated with critical aggregation concentration (CAC), which corresponds to the onset of micelle formation on the polymer. With increasing surfactant concentration, a second break indicating critical micelle concentration (CMC) was observed.