SMALL-ANGLE NEUTRON-SCATTERING AND VISCOSITY STUDIES OF CTAB NASAL VISCOELASTIC MICELLAR SOLUTIONS/

Micellar solutions of cationic surfactant cetyltrimethylammonium bromi de (CTAB) in the presence of sodium salicylate (NaSal) show a viscoela stic behavior. Small-angle neutron-scattering (SANS) and viscosity stu dies from CTAB/NaSal micellar solutions are reported. Zero-shear visco sity of these solutions as a function of Nasal concentration (C-s), at all the four measured surfactant concentrations (C-d) of 12.5. 25, 50 and 100 mM, show a double-peak behavior. The effect of C-s/C-d on two viscosity mar;ima and a minimum has been examined, and the scaling re lations are obtained. SANS experiments have been carried out at differ ent Nasal concentrations, beyond the first viscosity maximum for two s urfactant concentrations of 25 and 100 mM. It is found that micelles a re rigid rods and their exponential length distribution shows that the y behave as living polymers beyond the first viscosity maximum. The mi cellar structure does not change in the living polymer regime, whereas viscosity varies with increase in Nasal concentration. The variation in viscosity seems to be connected with the change in the intermicelle interactions.