“Tuliplike” Scattering Patterns in Wormlike Micelles under Shear Flow

Abstract

Using small angle light scattering we report on the formation of a string phase in a semidilute solution of wormlike micelles (0.03M CTAB͞0.24M NaSal) under simple shear flow. The string phase appears as a bright narrow streak in the scattering pattern normal to the flow direction. We also study the relaxation behavior after cessation of flow, and using the Brochard-de Gennes model we are able to estimate the stress relaxation time t s and diffusion coefficient D c of the dominant relaxation mode.[S0031-9007(96)00227-X]

Microstructure and rheology of a flow-induced structured phase in wormlike micellar solutions

“…For semidilute wormlike micellar solutions made with ionic surfactants, the addition of salt can lead to significant structural and rheological transitions (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Multiconnected and branched micellar networks have been observed at equilibrium.…”

“…Similarly, others observed birefringent SIS formation in a solution of surfactant and salt under shear and subsequent disappearance of the birefringent structures after the flow was stopped (24,37). Based on time-dependent SALS studies under a simple shear flow, Kadoma and van Egmond (12) suggested that CTAB/NaSal-based (0.03/ 0.24 M) SISs consist of highly elongated and locally concentrated micellar strings. The SIS has since been widely studied using birefringence, light scattering, neutron scattering, X-ray scattering, and NMR (21,24).…”

“…The ionic strength of the salt screens the electrostatic repulsions between the charged surfactant head groups, promoting cylindrical micellar growth (1)(2)(3). At higher salt concentrations, the entangled linear micelles can transition to branched and multiconnected micellar networks, as evidenced by rheological measurements, light scattering techniques, and electron microcopy (EM) imaging (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). Additionally, wormlike micellar solutions are known to exhibit a variety of interesting phenomena, some of which are shear banding (19)(20)(21), shear thickening (22,23), shear-induced transitions and instabilities (refs.…”

“…Additionally, wormlike micellar solutions are known to exhibit a variety of interesting phenomena, some of which are shear banding (19-21), shear thickening (22, 23), shear-induced transitions and instabilities (refs. 4, 24 and references therein), and flow-induced structure formation (3,(12)(13)(14)(25)(26)(27)(28)(29)(30)(31)(32). Wormlike micelles have also found applications in oil recovery, drag reduction, nanotemplating, and many biomedical and health care products (33-35).…”

Experimental Study of Pressure Loss and Rheo-Optical Behavior of CTAB/NaSal Aqueous Solution under Elongational Flow

“…[7][8][9][10][11][12] Kadoma et al [7][8][9] observed the change of SALS pattern at various shear rates (simple shear flow) with various excess salt ratios (Y) to investigate its effect on flow-induced orientation and concentration fluctuations for CTAB/NaSal solutions. They reported the relationship between several multiconnected networks of micelles and the SALS patterns.…”