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

Abstract

The rheological properties of aqueous systems composed of each of the four homologous cationic surfactants (3-alkoxy-2-hydroxypropyl trimethyl ammonium bromides, C n HTAB, n = 12, 14, 16 and 18) in the presence of an anionic surfactant, sodium octanoate (SO), have been studied by using steady state and frequency sweep rheological measurements. The effects of surfactant concentration, hydrophobic chain length and temperature were investigated. In C 14 HTAB solution, the viscosity shows shear thinning in the concentration range of C C14HTAB [320 mmol/kg. Addition of SO promotes the micellar growth and results in the generation of wormlike micelles. Zero-shear viscosity (g 0 ) of the binary surfactant system exhibits a maximum point in the investigated concentration range, suggesting the interaction between C 14 HTAB and SO molecules is strongest at the optimal ratio of C 14 HTAB with SO. The decrease in viscosity was attributed to be the transition from entangled wormlike micelles to branching micelles after the maximum point, cryo-TEM images revealed the changes in the structure of the wormlike micelles.

The Impact of Polyoxyethylene Sorbitan Surfactants in the Microstructure and Rheological Behaviour of Emulsions Made With Melted Fat From Cupuassu (Theobroma grandiflorum)

“…In addition, at higher fat concentrations the droplets tend to be packed fairly densely into the system [24]. Likewise, similar behavior has been reported for aqueous systems using a mixture of cationic and anionic surfactants [29] and for multilamellar vesicles (MLVs) [51,52]. Cupuassu fat (CF) sample and control emulsion (C80) showed almost Newtonian behaviour (n H C0.9) according to the H model, assuming that oils are usually Newtonian, but at very high shear rates, in the shear stress x shear rate diagram, there may be a curvature toward the axis of the shear rate, referring to the as pseudoplasticity [46].…”

“…Since emulsions are found in many products, it is important to understand their physical, rheological and microscopic properties in order to choose the best surfactants and process conditions and also the appropriate equipment to work with this type of colloidal system. For this purpose, determinations of the droplet size and rheology are probably the most important way to characterise them [13,[28][29][30]. In addition, these criteria depend on several parameters like the type and concentration of the surfactant and oil phase; in consequence, this influences other properties of emulsions such as stability, texture, appearance, taste, shelf life, etc.…”

Effect of Additives on Surfactant Micelle Shape Transformation: Rheology and Molecular Dynamics Studies

“…The dispersed rod-like micelles existed at the concentration value of 25 mmol L –1 at which the shear thinning phenomenon appeared. After the maximum viscosity, the reduction in viscosity with further addition of salts was usually ascribed to branching of the wormlike micellar induced by an increase in the end-cap energy, E c , − or shortening of the mean micelle size. − In general, in cationic surfactant/salt mixture solutions, the micellar branching could take place more easily when the electrostatic interactions were adequately screened because the branching point of micelles represented a delicate balance in the electrostatic property of the solution. The formation of a 3-fold micellar junction was greatly more favorable compared to the end-cap of a micelle .…”