Effect of surfactant concentration on the formation and viscoelasticity of anionic wormlike micelle by the methods of rheology and freeze-fracture TEM

Abstract

found that the addition of salt to aqueous cationic surfactant weakens electrostatic interactions and enhances micellar growth, in which the spherical surfactant micelles undergo a transition to larger rodlike aggregations with a molar weight of about 10 6 , named as wormlike micelles. They have high surface activity, high viscosity, and the property of shear thinning, which make them have such wide uses in many fields that people pay more and more attention to them. However, for anionic micelles, there are fewer reports.Recently, we have been interested in the micellar growth induced by an increase in the amount of anionic surfactant, sodium dodecyl trioxyethylene sulfate (SDES), and salts, AlCl 3 , CaCl 2 , MgCl 2 , KBr, NaCl, etc. in systems where wormlike micelles or network structures are formed. In this work, rheological methods and freeze-fracture transmission electron microscopy (FF-TEM) were applied to investigate the effect of surfactant concentration on the formation and viscoelasticity of wormlike micelles and network structures in anionic surfactant SDES aqueous solutions in the presence of the multivalent counterion electrolyte AlCl 3 . Some interesting and noticeable conclusions will enrich the theory and application of wormlike micelles.Abstract Wormlike micelles and network structures were obtained for the samples with the anionic surfactant, sodium dodecyl trioxyethylene sulfate (SDES), and multivalent counterion electrolyte AlCl 3 fixed in a proper concentration according to rheological measurements and the technique of freeze-fracture transmission electron microscopy (FF-TEM). The characteristics of a non-Newtonian fluid and the phenomenon of shear-induced structures transition were acquired from the steady-shear experiments. The TEM micrographs show the coexistence of wormlike micelles, entangled network structures, rod-and sphere-like micelles in the solutions.The Cole-Cole plot shows the rheological behavior of the non-linear viscoelasticity, the departure from the Maxwell model, and a relaxation time that is not simple. The plateau modulus G 0 and the relaxation time s were also investigated to express the rheological properties of the wormlike micellar solutions.

Alkyl chain length-dependent viscoelastic properties in aqueous wormlike micellar solutions of anionic gemini surfactants with an azobenzene spacer

“…The micelles are approximately smaller than 10 nm in diameter and seem to be very long in length. These are similar to the wormlike micelles formed by SDES (sodium dodecyltrioxythylene sulfate) with addition of AlCl 3 , whose loss modulus G 00 also dominated over the storage modulus G 0 at x < 100 rad s À1 [25]. For C 12 (azo)C 12 (Fig.…”

Rheological Properties of Wormlike Micelles Formed in Aqueous Systems of 3‐Alkoxy‐2‐hydroxypropyl Trimethyl Ammonium Bromides in the Presence of Sodium Octanoate

“…These experimental results fully show that the hydrophobic interaction is strengthened with increasing alkyl chain length and long wormlike micelles and a gel is easier to form in the system. This gelation behavior may be attributed to the crystallization of wormlike micelles, which is related to the strong synergic interaction between both the surfactants under the Kraft point of C [16][17][18] HTAB [44,45]. When the temperature is increased to above 35°C, both the samples exhibits characteristic wormlike micelle features with strong viscoelastic behavior.…”

Shear rheology and porous media flow of wormlike micelle solutions formed by mixtures of surfactants of opposite charge

“…Such behavior has been reported for cationic surfactants and, in particular, the decrease in viscosity has been attributed to the formation of branched micelles. It has been argued that branched micelles cause the formation of slippage points, allowing for a faster relaxation of the structures [15][16][17][18][19][20]. It could be argued that the viscosity drop is due to the reduction of the micellar radius of gyration, which could be attributed to the increased flexibility of the relatively long micelles and their polyelectrolytic nature [4,[21][22][23].…”