Micellar growth of octaethylene glycol decyl ether

Abstract

The micelle formation of C₁₀E₈, a non-ionic surfactant, has been investigated with Sephadex G-10 by frontal gel-filtration chromatography (GFC) at 298 K. From analysis of the concentration dependence of the centroid volume of the GFC pattern by asymptotic theory, the monomer concentration, C₁, of C₁₀E₈ is determined as a function of total concentration, C. From the relation between C₁ and C, the weight-average aggregation number, n_w, of C₁₀E₈ micelles is estimated as a function of C. The n_w value increases rapidly above the critical micelle concentration (c.m.c.) and levels off at higher concentrations. The derivative GFC pattern also suggests the formation of small micelles (probably dimer) at low concentrations below the c.m.c. These results are explicable by the Tanford theory for the formation of spherical micelles and its modified theory. The micelle size distributions are calculated from these theories. Values of c.m.c. calculated on the basis of a few definitions of the c.m.c. are compared with the observed value.