Rheology of surfactant solutions

Wang SQ, Hu YT, Jamieson AM (1994). In Rheology of Surfactant Solutions, Herb CA, Prud homme RK, (eds), ACS Symposium Series 578, American Chemical Society, Washington, DC, p 278. 

Hoffmann H, Lobl H, Rehage H, Wunderlich I (1985) Rheology of surfactant solutions. Ten-side Detergents 22 290-298... 

It is necessary here to point out that the rheology of all materials, especially the rheology of surfactant solutions, can depend strongly on the time-scale on which the material is studied. This can be demonstrated quite easily. For example, Newtonian liquid water behaves as an elastic solid if the stress is applied for nanoseconds or picoseconds on the other hand, granite, which can be regarded as an Euclidean solid to a first approximation, can flow like a liquid if a strong stress acts over a period of 10 -10 years. Therefore, it must be stated at this point that the description of the rheological effects of surfactant solutions is valid for observation times which are necessary for the measurements, i.e. several seconds up to several days, or weeks in some cases. 

CMCs in the absence of added electrolyte may be greatly influenced by electrovis-cous effects marked decreases in intrinsic viscosity on electrolyte addition have been observed in many cases36). Peculiar and highly interesting rheological properties of surfactant solutions include observations of strongly non-Newtonian behavior as well as of viscoelasticity these are yet incompletely understood. 

Very few rheological data have been reported for ordered cubic phases of surfactant solutions. However, Radiman et al. (1994) have reported dynamic oscillatory data for solutions of didodecyldimethylammonium bromide (DDAB) in deuterated water and octane. Their data for type II cubic P and D phases are shown in Fig. 12-29. They report that the samples... 

It has often been stated that DR of surfactant solutions is related to their rheological properties. A rise in shear viscosity at a critical shear rate, caused by a shear-induced structure (SIS), viscoelasticity (nonzero first normal stress difference, quick recoil, and stress overshoot), and high extensional viscosity/shear viscosity ratios ( 100) are rheological properties found in many DR surfactant solutions. After reviewing the rheological behavior of many DR surfactant solutions, Qi and Zakin concluded that SIS and viscoelasticity are not always observed in DR surfactant solutions while high extensional/shear viscosity ratios may be a requirement for surfactant solutions to be DR. ... 

Over the past few decades there has been an increase in the research tools for fundamental rheology studies of surfactant solutions and commercial detergent formulations. The coupling of rheometers with other methods has broadened the range of studies that can be completed, leading to a better understanding of solution properties, self-assembled mesophases, multiple-component dispersions, and gels. 

In an early part of this chapter, the responses of surfactant solutions to the mechanical stress or strain was described. The influence of the various structures in these systems on their rheological behaviour was... 

The rheological properties of surfactant solutions are impacted strongly by the types of aggregates formed in solution. The viscous and viscoelastic... 

The next section discusses chemical structures, synthesis, and purification of gemini surfactants. Section III reviews the behavior of gemini surfactants in solutions below the CMC. Section IV deals with their behavior at interfaces. The fifth section reviews micelle formation and solubilization. Section VI deals with micelle properties. Microstructure of aqueous solution of gemini surfactants, rheology of these solutions, and mixed micellization are considered in the following three sections. Section X deals with the phase behavior of... 

VIII. RHEOLOGY OF AQUEOUS SOLUTIONS OF GEMINI SURFACTANTS... 

As a rule, dynamic processes with fluid interfaces are accompanied by interfacial dilatation, compression, and/or two-dimensional flows in the surfactant adsorption mono-layer. These processes are affected by the interfacial rheological properties, such as surface (Gibbs) elasticity, dilatational, and shear-surface viscosity, and adsorption relaxation time see Sec. III.F. The interfacial rheological properties are especially important for the foaminess of surfactant solutions and the emulsion preparation by homogenization. 

Using the drop and bubble profile analysis tensiometer PAT-1 (SINTERFACE Technologies, Berlin, Germany) it is possible to perform dilational rheology studies of surfactant solutions at low frequencies. 

Molecularly motivated empiricisms, such as the solubility parameter concept, have been valuable in dealing with mixtures of weakly interacting small molecules where surface forces are small. However, they are completely inadequate for mixtures that involve macromolecules, associating entities like surfactants, and rod-like or plate-like species that can form ordered phases. New theories and models are needed to describe and understand these systems. This is an active research area where advances could lead to better understanding of the dynamics of polymers and colloids in solution, the rheological and mechanical properties of these solutions, and, more generally, the fluid mechaiucs of non-Newtonian liquids. 

Effect of addition of homopolymer, salt or conventional surfactants The effect of addition of PEO and PPO homopolymers on the gel formation of Pluronic F127 (defined in Fig. 4.3) in aqueous solution has been studied by Malm-sten and Lindman (1993). The structure, studied via SANS, and rheology of neat F127 solutions in the concentration range 10-20% has been probed by Prud homme et al. (1996). Addition of PEO can reduce the gel region and/or eliminate it at sufficiently high PEO concentration. The amount of PEO required to melt the gel depends on the copolymer concentration and decreases with... 

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