Organization of amphiphiles, Part-II: Surface activity of polyoxyethylated alkyl phenols at air-water interface

Abstract

The surface properties of a series of polyoxyethylated alkyl phenols la [C 8 H 1 7 -O(CH 2 CH 2 O) n -H, n = 10, 30] and lb [C 9 H 1 9 -O(CH 2 CH 2 O) n -H, n= 10, 15, 20, 40] have been studied through surface tension measurement by Wilhelmy plate method. The surface pressure values calculated from surface tension data have been fitted to Gibbs adsorption equation and the standard free energies of micellization and adsorption at air water-interface have been calculated. The minimum area per surfactant molecule and critical micellar concentration reveal that both steric constraints and hydrophobicity of the surfactant play a major role in micelle formation.