Analogy between Aqueous Solutions of Surfactant Micelles and Semidilute Polymer Solutions

Abstract

By static and dynamic light scattering, were measured osmotic compressibility, static correlation length, and hydrodynamic correlation length of aqueous solutions of heptaethyleneglycol monotetradecyl ether (C₁₄E₇) as a function of concentration ranging from 1 x 10^-3 g rn/-' to 0.1 gm/^-1 at various temperatures ranging from 35 to 55 °C. To make a quantitative examination of applicability of scaling and screening concepts to micellar systems, the results were compared with those of semidilute solutions of polystyrene in t-decalin near the thetatemperature with the aid of equations proposed here on the basis of the scaling theories for polymer solutions. The following conclusions have been deduced: ( 1 ) The present micellar solutions are not in the asymptotic scaling region, but in the crossover region from the poor- to good-solvent regions. ( 2 ) Osmotic compressibility and static correlation length of the micellar solutions can basically be described by the equations presented here covering the critical and the tri-critical semidilute regions, in common with those of polymer solutions. '( 3 ) Molecular parameters in these equations obtained suggest increase in the statistical segment length with increasing temperature.