Rheo-Optic Behavior of Wormlike Micelles under a Shear-Induced Structure Formational Condition. Verification of stress-optic rule by full component measurement of refractive index tensor.

Abstract

An aqueous cationic surfactant solution, CTAB/NaSal, forms wormlike micelles and shows viscoelastic properties. It also shows shear-induced structure change at shear rates higher than 4 s-1. Full components of the refractive index tensor under step shear flow were measured by using double-beam rheo-optical analyzer in addition of shear stress and first normal stress difference measurement. Each component of the refractive index tensor is proportional to the corresponding component of the stress tensor when shear rate is lower than 6 s-1. However, a stress-optical coefficient, C, suddenly decreases above 4 s-1. At shear rates between 4 to 6 s-1 , the stress-optic rule holds, but micellar structure might change.

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

“…Therefore, other potential relaxation time scales from the length/ concentration fluctuation of micelles might also be responsible for the stress response we observed earlier. Investigations of spatial resolution of heterogeneous bands, formation of shear induced structure phase [Ouchi et al (2006a); Takahashi and Sakata (2011)] and localization of stresses at different deformations by rheo-optics [Ouchi et al (2006b); Takahashi et al (2002Takahashi et al ( , 2001] will be considered in the future work to correlate shear stress and flow-birefringence, and flow instability in the CTAB/SHNC system. Concentration fluctuation and shear induced bond formation should be studied to further explore the transient behavior of highly viscoelastic hydrotropic micellar system.…”

A rheo-optical study of shear rate and optical anisotropy in wormlike micelles solutions

“…In this approach the shear rate is inferred from the degree of alignment. Orientational ordering has been examined using flow birefringence, [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] small angle light scattering (SALS), 14,22,[30][31][32][33] small angle neutron scattering (SANS) 15,27,[34][35][36][37] and NMR. 6,8,38 Flow birefringence and NMR have been used to spatially resolve ordering across a sheared solution.…”

Effect of Surface Treatments on Viscoelastic Measurements of Thread-like Micellar Solutions

“…One of the well-known examples is aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal). as flow birefringence [4][5][6] , flow light scattering [7][8][9] , and flow visualization 10,11) have been widely utilized. These apparatus normally have the glass windows to transmit the light.…”