The Influence Of Inorganic Salts On The Rheological Properties Of The Catanionic Surfactants Mixed Systems

In this thesis, phase behavior and rheological properties of the mixed propanediyl-a,ω-bis(dodecyl dimethyl ammonium bromide)(12-3-12,2Br) /sodium dodecyl sulfonate(AS) and alkyltrimethyl ammonium halide/ alkali dodecyl sulfonate systems were investigated, and the influence of the chain length of surfactants, inorganic ion specific effect and temperature on the rheological properties were discussed. Meanwhile, the relationship between aggregates microstructures and the rheological properties have been explored.1. At 318.15 K, the phase behaviors and rheological properties of 0.10 mol·kg-1 12-3-12,2Br/H2O system and 12-3-12,2Br/AS mixed systems with NaBr and Na3PO4 of different concentrations were measured. The experimental results indicated that different from the conventional quaternary ammonium bromide, gemini surfactant 12-3-12,2Br can spontaneously aqueous two-phase separate in aqueous solutions of inorganic salts when the concentration of NaBr increases to about 0.28 mol-kg-1, or Na3PO4 increases to about 0.93 mol-kg-1. The aqueous two-phase region and shear viscosity maximum peak at isotropic single-phase region for 12-3-12/AS/H2O mixed systems with excess 12-3-12,2Br shift far from the equimolar composition with the addition of salts. The value of the shear viscosity maximum peak decreases with the increase of the salt concentration. Meanwhile, when the inorganic salt concentration increases to a certain amount, the shear viscosity peak disappeared. In the process of salt-induced aqueous two-phase separation of the isotropic 12-3-12,2Br solutions, with the increase of inorganic salt concentration, shear viscosity maximum peak was observed, the rheological behaviors of these isotropic solutions varied from nearly Newtonian fluids to antithixotropic fluids to nearly Newtonian fluids (close to shear viscosity peak) to thixotropic fluids (near the phase boundary of ATPS region). For the isotropic aqueous mixed 12-3-12,2Br/AS/salt systems with excess 12-3-12,2Br, at low salt concentrations, with the addition of AS, the rheological behaviors of the systems varied from nearly Newtonian fluids to antithixotropic fluids to complex thixotropic fluids to thixotropic fluids. At high salt concentrations, for the rheological behaviors of the mixed isotropic systems, the changing tendency is different due to the different rheological behaviors of 12-3-12,2Br saline solution in comparison with those at low salt concentration. However the isotropic systems near the phase boundary of ATPS region are all thixotropic, from the viewpoint of rheological behavior, the aqueous two-phase systems originate from thixotropic fluids. Compared with Na3PO4, the influence of NaBr on the phase behaviors and rheological properties is more significant, which is related to the matching of water affinity between the surfactant ionic head groups and inorganic counterions.2. The influences of constituent inorganic ions for the CTAC/AS/H2O and the CTAB/AS/H2O mixed system on the phase behavior and rheological properties have been investigated. Results indicate that the aqueous two-phase and shear viscosity maximum peak shifted far from the equimolar line as increasing of salt concentration (NaCl, NaBr), and shear viscosity maximum peaks of the systems at isotropic single-phase region with AS in excess are less than those of cationic surfactant in excess. Shear viscosity maximum peak of the systems at isotropic single-phase region with AS in excess change as follows:at first, the value of shear viscosity maximum peak increased with increasing of salt concentration(NaCl, NaBr), and the shear viscosity peaks remain almost unchanged when the salt concentration reaches a certain amount. For the CTAC/AS/H2O mixed system with CTAC in excess, the peak increased with the addition of NaCl, however the tendency of viscosity increases become slow. For the CTAB/AS/H2O mixed system with CTAB in excess, with the addition of NaBr, the viscosity peaks of the isotropic single-phase region increase firstly, and then decrease. The shear viscosity maximum peaks are related to the chain length and interactions between oppositely charged surfactants, and the influence of electrostatic screening on the interaction between surfactant ionic head-groups were discussed.3. The influences of the chain length on rheological properties of quaternary ammonium bromide (dodecyltrimethyl ammonium bromide DTAB, cetyltrimethyl ammonium bromide CTAB, octadecyltrimethyl ammonium bromide STAB)/AS mixed systems have been investigated, and inorganic specific ion effects on the phase behaviors and rheological properties of CTAY/XAS/H2O mixed systems with different inorganic counterions also have been studied. Results indicate that the formation of wormlike micelles is easier with the increase of the chain length, and thus increases the shear viscosity maximum peak. For the CTAY/AS/H2O(Y=F-Cl-, Br-NO3-, (1/2SO4)-) mixed systems with CTAY in excess and CTAB/XAS/H2O(X=Li+, Na+, K+) mixed system with XAS in excess, the inorganic counterions effects on the aqueous two-phase regions and the shear viscosity maximum peak of isotropic single-phase regions are related to the matching of water affinity between surfactants ionic head groups and inorganic counterions, and meanwhile, the above results have been discussed according to Collins concept of the matching of water affinity.