Effect of molecular structure of amphiphiles on the surface pressure and electric surface potential isotherms at the air/solution interface

Surface pressure (π) and electric surface potential (ΔV) isotherms of soluble surfactants, when presented in concentration scale normalized with respect to half surface coverage concentration, cnorm = c/cΘ/2 (which may conveniently be derived from Frumkin model), enable examination of differences in shape caused by amphiphiles' different structure. The coverage Θ ≤ 50% makes at the most 25% of the total π and 50% of the total ΔV change.