Viscosity Increase with Temperature in Cationic Surfactant Solutions Due to the Growth of Wormlike Micelles

Abstract

Wormlike micellar solutions based on ionic surfactants typically show an exponential decrease in viscosity upon heating. Here, we report the unusual observation of an increasing viscosity with temperature in certain cationic wormlike micellar solutions. The solutions contain a cationic surfactant with an erucyl (C22, mono-unsaturated) tail and an organic salt, sodium hydroxynaphthalene carboxylate (SHNC). When these solutions are heated, their zero-shear viscosity increases over a range of temperatures. In some cases, the viscosity reaches a peak at a certain temperature and then decreases with further heating. The magnitude of the viscosity increase, the onset of this increase, and the peak temperature can all be tuned by varying the SHNC concentration. Small-angle neutron scattering is used to study the origin of this unusual rheological behavior. The data reveal that the contour length of the micelles increases with temperature, in tandem with the rise in viscosity. A possible explanation for the contour length increase, based on a temperature-dependent counterion binding, is discussed.

Rheological characterizations of wormlike micellar solutions containing cationic surfactant and anionic hydrotropic salt

“…These noncovalent bonds are much stronger than hydrogen bonds, and can increase the shear viscosity and micelle relaxation time of CTAB/SHNC solutions significantly. This argument can be applied to another set of sample parameters: the g 0 and G 0 in 60 mM CTAB/SHNC solution are comparable with those in 100 mM CTAB/NaSal solution, but the relaxation time s r in 60 mM CTAB/SHNC solution is much longer when compared with that of 100 mM CTAB/NaSal solution, due to stronger interactions between noncovalent bonds and high viscosity in the CTAB/SHNC solution which hinder the breakup of micelles in the system [Kalur et al (2005)]. …”

“…À ions have shown sensitive temperature responses: HNC À ions can desorb from the micellar surface, where p-p and cation-p bonds between micelles become weakened with increasing temperatures with excessive HNC À in a micellar solution [Kalur et al (2005)]. Here, we employed both startup shear and shear hysteresis flow procedures to probe the transient rheology behavior of 75 mM CTAB/SHNC solution.…”

“…As a result, CTAB/SHNC mixtures have shown complex rheological behavior that is associated with higher surface activity and extra intramolecular interactions of micelles [Kalur et al (2005); Verma et al (2011)].…”

Adsorption Performance of Methyl Violet via α-Fe2O3@Porous Hollow Carbonaceous Microspheres and Its Effective Regeneration through a Fenton-Like Reaction

“…By and large, a slight increase of the value of p/% can be observed with the increase of temperature at the same initial concentration, and the removal rate seems to decrease with increasing concentration under the same temperature. Generally, the viscosity of the solution decreases as the temperature rising, leading to the increasing rate of intraparticle and interparticles diffusion [28]. Moreover, an increase in the mobility of the dye molecules facilitates the dye molecules to move to the adsorbent surface, which causes an increase in the removal efficiency as the solution temperature increased.…”

Thermo-responsive Wormlike Micelles

“…2.4a) [2,7,9,50,51], erucyl bis-(hydroxyethyl)methylammonium chloride (EHAC, Fig. 2.4b) [3] or CTAB ( Fig. 2.4c, d) [4,52] in the presence of strongly hydrophobic organic compounds: 3-hydroxynaphthalene-2-carboxylate (HNC − , Fig.…”