Intermicellar Migration of Surfactant Molecules in Entangled Micellar Solutions

Abstract

Surfactant self-diffusion coefficients (D) have been measured on semidilute solutions of nonionic surfactants (C 16 E 7 , C 14 E 7 , and C 14 E 6 ) at different temperatures by using the pulsed-gradient spin echo method. The self-diffusion coefficient of these surfactants first decreases with increasing concentration (c) and then increases. Above about 10% by weight, the log D-log c plot gives a straight line whose slope is in good agreement with the theoretical prediction (2/3) of the previously reported model which takes into account intermicellar migration of surfactant molecules. In order to simulate the observed diffusion coefficient in the whole concentration range, this model has been modified by taking into account the micellar diffusion