On the Theory of the Concentration Dependence of the Self-Diffusion Coefficient of Micelles

Abstract

A theory is given for the ratio of initial slope to intercept in a plot of 1/D versus concentration of colloid particles; D is the self‐diffusion coefficient of the charged colloid particles (micelles). The theory starts from the Einstein relation, and the autocorrelation function expression for the friction constant. The main approximation is the use of Brownian motion theory to describe the effect of the solvent on micelle motion. There is good agreement with experiment in salt solutions, but the agreement is poor when there is no added salt. It is concluded that the theory is probably appropriate for solutions of high ionic strength, but the possibility that the data in salt‐free solution have not been interpreted properly, i.e., that the theory has a wider validity, is also discussed.