Effect of silica colloids on the rheology of viscoelastic gels formed by the surfactant cetyl trimethylammonium tosylate

Abstract

The effects of the addition of submicrometer-sized colloidal silica spheres on the linear and nonlinear rheology of semidilute solutions of a viscoelastic gel are studied. For a 1.4 wt% solution of the surfactant CTAT, a peak in the zero-shear rate viscosity eta(0) is observed at approximately equal weight percents of silica and CTAT. This peak shifts to lower silica concentrations on increasing either the CTAT concentration or the surface charge on silica and disappears when the CTAT concentration is increased to 2.6 wt%. The increases in eta(0) and the high frequency plateau modulus G(0) on the introduction of SiO(2) are explained by considering the increasingly entangled wormlike micelles that are formed due to the enhanced screening of the electrostatic interactions. The observed decrease in the values of G(0) and eta(0) at higher concentrations of silica particles is explained in terms of the formation of surfactant bilayers due to the adsorption of the positively charged cetyl trimethylammonium to the negatively charged silica.

Nanoparticles induced micellar growth in sodium oleate wormlike micelles solutions

“…Herein, we found that the organic additive of OTAB was much more efficient in inducing the NaOA micellar growth than the inorganic Na 2 CO 3 . Compared with the previous studies on the mixtures of nanoparticles and wormlike micelles, most of them employed are cationic surfactants and opposite charged nanoparticles [19,20,22] that suffered serious disadvantages and limited their applications [15]. The present work showed detailed information about the interactions between anionic wormlike micelles and positivecharged nano SiO 2 , in which the presence of nano SiO 2 can also facilitate branched wormlike micelles formation in the NaOA/OTAB system as confirmed by rheology and cryo-TEM results.…”

“…The present work showed detailed information about the interactions between anionic wormlike micelles and positivecharged nano SiO 2 , in which the presence of nano SiO 2 can also facilitate branched wormlike micelles formation in the NaOA/OTAB system as confirmed by rheology and cryo-TEM results. Compared with the previously reported cationic type systems [19,20,22], this anionic type nanoparticles and wormlike micelles mixtures may extend their applications in many fields, especially in that of crude oil recovery.…”

“…The participation of nanoparticles participated in the wormlike micelles by forming the structure of cross-links or double networks was also reported [20]. Indeed, colloidal as well as non-Brownian particles are added to wormlike micelle solutions at very low concentrations to probe the local structure and viscoelasticity of the network microrheology [19,21,22]. Smart fluids based on surfactant wormlike micelles and oppositely charged magnetic particles were reported as well [23,24].…”

“…For example, pyroelectric nanoparticles [18] can make the wormlike micelles retain high viscosity at elevated temperature due to the electrostatic interactions between the surfactant and silica particles [19]. The participation of nanoparticles participated in the wormlike micelles by forming the structure of cross-links or double networks was also reported [20].…”

“…The mixture of NaOA and OTAB is selected to investigate the effect of nanosized silica particles (nano SiO 2 ) on the wormlike micelle formation. Though similar nanoparticles-induced wormlike micelles branching are well known due to the electrostatic interaction, however, most of the employed systems are cationic surfactants and opposite-charged nanoparticles [19,20,22] that suffered serious disadvantages and limited their applications [15]. As the best of our knowledge, it is the first report on the interaction between negative-charged nanoparticles and anionic surfactant wormlike micelles.…”