DYNAMIC LIGHT-SCATTERING OF CTAB/NASAL LONG THREAD-LIKE MICELLES IN THE SEMIDILUTE REGIME - APPLICABILITY OF THE DYNAMIC SCALING LAW

Dynamic light scattering experiments were done to study dynamic aspects of networks formed by long threadlike micelles of cetyltrimethylammonium bromide (CTAB) in aqueous sodium salicylate (NaSal) solutions at three temperatures, T, of 25, 40, and 60-degrees-C. The surfactant concentration, C(D), of six solutions tested was fixed at 0.01 M, and a ratio of salt concentration, C(s), to C(D) Was varied from 1 to 41. The cooperative diffusion coefficient, D(c), was obtained from extrapolation of the first cumulant, GAMMA(e),/q2, to the zero scattering vector q. The D(c) showed complicated C(S)/C(D) dependence with a minimum at C(S)/C(D) = 10 that was followed by a maximum at C(S)/C(D) = 20, while it monotonically increased with increasing T. All GAMMA(e) data of the solutions With C(S)/C(D) = 1-41 at three temperatures were found to be superposed on one master curve in making a reduced plot of GAMMA(e)/q2D(c) vs qxi(H), where the dynamic correlation length, xi(H), was estimated from D(c). The master curve was found in agreement with the theoretical prediction developed for chain dynamics of linear flexible macromolecules in the semidilute regime.