A new strongly flow birefringent surfactant system

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

“…Due to closer proximity and better interactions between carboxyl (position 2) and hydroxyl (position 3) groups in SHNC molecules, stronger bonds from p-p and cationÀp interactions can be formed in SHNC-cationic surfactant micelles, yielding changes in the size and shape of micellar aggregates in the solution [Gravsholt (1976)]. To validate this argument, HNMR (Hydrogen Nuclear Magnetic Resonance) spectra show that one of the benzene rings strongly adsorbs on the surface of cationic micelles with the other one connected with carboxyl and hydroxyl groups protruding out of the micelles, serving as an extra "tail" because its length is comparable with that of CTAB tails [Mishra et al (1993a)] (see Fig. 1).…”

“…In addition, mixtures of cationic surfactant and excess amount of SHNC have shown pronounced birefringence phenomena lasting from milliseconds up to even hours after the flow stoppage [Frounfelker et al (2008); Mishra et al (1993a)]. Recent studies have used light scattering, flow birefringence, electron microscopy, and rheometric techniques to investigate the material properties of SHNC and cationic surfactant mixtures.…”

“…Recent studies have used light scattering, flow birefringence, electron microscopy, and rheometric techniques to investigate the material properties of SHNC and cationic surfactant mixtures. Mishra et al (1993aMishra et al ( , 1993b reported the phase behavior of the mixture of cationic surfactant cetyltrimethylammonium bromide (CTAB) and SHNC. By fixing the CTAB concentration at 60 mM and gradually increasing the CTAB/SHNC molar ratio, the CTAB/SHNC mixture underwent phase transitions from small micellar aggregates to a positively charged gel phase, followed by a liquid crystalline lamellar phase, then precipitated into a multilamellar vesicle phase at equimolar surfactant/salt concentration.…”

“…By fixing the CTAB concentration at 60 mM and gradually increasing the CTAB/SHNC molar ratio, the CTAB/SHNC mixture underwent phase transitions from small micellar aggregates to a positively charged gel phase, followed by a liquid crystalline lamellar phase, then precipitated into a multilamellar vesicle phase at equimolar surfactant/salt concentration. In particular, when the concentration ratio of SHNC over cationic surfactant exceeds 1.0, SHNC was observed to inhibit growth or entanglement of micelles by negatively charging micelle surfaces [Abdel-Rahem (2005); Krishnaswamy et al (2005); Mishra et al (1993aMishra et al ( , 1993b]. When the temperature increases or the solution is further diluted, the HNC À ions can actually desorb from the micelles and decrease the surface charge of micelles, which in turn promotes growth of wormlike micelles and enhances the viscoelasticity of the solution.…”

Effect of ionic strength on rheological behavior of polymer-like cetyltrimethylammonium tosylate micellar solutions

“…1 The addition of inorganic salts to ionic surfactant solutions screens the repulsions between the charged heads and decreases the concentration at which the transition from spherical to rod-like micelles occurs. [2][3][4][5][6][7] This transition takes place at even lower concentrations in the presence of organic (hydrotropic) salts or in surfactants with counterions such as salicylate, 3,[8][9][10] tosylate, 11 chlorobenzoate, 12 hydroxyl naphthalene carboxylate, 5,13 and alkyl sulfates 14 without the addition of electrolytes. The intensity of binding to the micelles is a function of the hydrophobicity of the counterion.…”