Micelle formation of detergent molecules in aqueous media: viscoelastic properties of aqueous cetyltrimethylammonium bromide solutions

Abstract

Viscoelastic properties of aqueous solutions of cetyltrimethylammonium bromide (CTAB) containing sodium salicylate (Nasal) were examined by varying the CTAB, CD, and Nasal, CS, concentrations. The results were compared with those of flexible-chain polymer solutions. With increasing salt-to-detergent ratio, C&D-l, up to a certain critical value close to 1 for the solutions of a given CD, the rheological behavior changed from that of low molecular weight polymer solutions in which the polymer chains are not entangling to behavior similar to that of high molecular weight polymer solutions in which polymer chains are fully entangling. These results suggest that threadlike micelles composed of CTAB/NaSal complexes began to form as C8Cp-l increased, resulting in an entanglement network exhibiting pronounced viscoelasticity. However, at high CSCD-~ above the critical value, their behavior can be represented by a Maxwell model with a constant plateau compliance JNO and a single relaxation time 7,. Interestingly, JNo waa proportional to CD-2.2 but independent of CSCD-', but the relaxation time 7 , decreased with increasing CSCD-l. The complex dependence of 7 , of all the solutions at high CSCD-~ may be reduced to a single composite function of CSC~-'/~. These results suggest that relaxation of the entanglement network took place by chemical processes involving actual breakdown and re-formation of the threadlike micelles.

Shear rheology and phase behaviour of sodium oleate/water mixtures

“…On the other hand, the slope of the power-law region of flow curves for some dilute worm-like micelles (i.e. long and flexible cylinders) of cationic surfactants/water systems [18,19] was found to be ca. 0.89.…”

Salt-concentration dependence of the structure and form factors for the wormlike micelle made from a dual surfactant in aqueous solutions

“…When the contour length of the cylinder becomes long enough to form entanglement between the cylinders, the characteristic viscoelasticity emerges (Shikata et al, 1987). Fig.…”

Adhesion and Growth Phenomena of Gel-like Materials Induced by Injection of NaSal into Flow of Aqueous Solution of CTAB

“…Considering the experimental results 3,4) that a wormlike micelle in CTAB/NaSal solutions is 1:1 complex of CTA + and Sal -and free salicylate ions in the solution affect the formation of micelle networks, we believe that free salicylate ions take an important role in the adhesion phenomenon. Although it is not clear whether the relaxation mechanism is relevant to the results in Fig.…”

“…Furthermore when excess of salt is added to a CTAB solution, wormlike micelles entangle to form networks, which show gel-like structures under some conditions. CTAB/NaSal systems have strong viscoelasticity [3][4][5][6] and…”