Microrheology of wormlike micellar fluids from the diffusion of colloidal probes.
The microrheology of cationic micellar solutions has been investigated as a function of added organic salts using quasielastic light scattering (QELS). Two organic salts, sodium p-toluene sulfonate and sodium salicylate, were used to induce microstructural changes in cetyl trimethylammonium bromide (CTAB) micelles. The mean-squared displacement (MSD) of polystyrene probe particles embedded in CTAB micellar solutions was monitored by QELS in the single-scattering regime. Through the use of the generalized Stokes-Einstein relationship, the frequency-dependent complex shear moduli of each fluid were estimated from the Laplace transform of the corresponding MSD. The salt-induced transition from nearly spherical to elongated wormlike micelles and consequent changes in fluid response from viscous to viscoelastic are clearly captured by microrheology.
Hassan
P A
PA
Novel Materials and Structural Chemistry Division and Applied Chemistry Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085, India. hassan@apsara.barc.ernet.in
Bhattacharya
K
K
Kulshreshtha
S K
SK
Raghavan
S R
SR