| Studies of the strong interactions between cationic/anionic surfactants and their complex phase behavior are of considerable interest. Quaternary ammonium Gemini surfactants exhibit peculiar properties because of novel molecular structures. At present, however, few studies are focus on the mixture of cationic/anionic surfactants containing Gemini component. With the financial support form Nature Sciences Foundation of China (sanction: 20173010) and Fujian Province Nature Sciences Foundation of China (sanction: E0110012), a system of C12-s-C12(2Br(s=2,3,4,6)/SDS mixed aqueous solutions has been systematically investigated, including the phase behavior, the micellization and their rheological properties. The main results are as follows:1) Phase boundaries between homogeneous and heterogeneous regions of C12-s-C12(2Br(s=2,3,4,6)/SDS mixed systems were determined. Three distinct concen- tration regions were observed, in which the homogeneous transparent solutions are formed at very low and relative high concentrations respectively, but heterogeneous region is found at mediate concentrations. The ability forming homogeneous solutions are enhanced when C12-s-C12(2Br is excessive. In most regions of low concentration, precipitation often occurs when total concentration (CT) is slightly larger because of the strong interaction between the two components. However, C12-3-C12(2Br/SDS appears quite different phenomenon compared with all other systems. When C12-3-C12(2Br is excessive, the mixed aqueous solution keeps homogeneous transparent until very high concentration.2) Technique of time-resolved fluorescence quenching (TRFQ) and fluorescence polarization, which were used to determine micelle aggregation number and to obtain microviscocity in the core of micelle, were optimized in the present work. This providedthe foundation for studying the mixed micellization of C12-s-C12(2Br/SDS in aqueous solutions.3) The treatment in terms of the regular solution theory was demonstrated to be suitable for the mixed surfactants system containing Gemini component. Thus the values of the molecular interaction parameter ((M) and the mole fraction (XMi) of i component in the mixed micelle were calculated according to the above theory.4) With addition of SDS, it interacts with C12-3-C12(2Br resulting in a formation of the mixed micelles. The values of I1/I3 in the aqueous micellar solutions were found to be close to that of conventional surfactants, which means their structures are similar. The interaction parameter ((M) calculated by the regular solution theory is about (13.6 ~ (19.2, which indicates that there is a synergism between the molecules in the mixed micelle, thus enhances the micelle formation. At a fixed total concentration (CT) of surfactants, with increasing the mole fraction ((SDS) of SDS in the bulk solution, the total critical micelle concentration (cmcT) decreases, the total micelle aggregation number (NT) as well as the micelle mole fraction (XMSDS) increase gradually, but the hydrodynamic radius (R() of the mixed micelle and its intrinsic viscosity ([(]) decrease, which indicates those molecules in the mixed micelle are packed more tightly. The results of microviscosity ((M) supported the above conclusion.At given (SDS, the curve of I1/I3(logCT appeared an S-type with increasing CT beyond cmcT. All the values of NT, [(], (M as well as the average effective specific volume (V) increase with CT and finally reached a maximum. Combining these results, the reason appeared the S-typed curve of I1/I3(logCT can be reduced to growing up of the micelle in size and forming more tightly packed structure. The Concentrations producing an abruptly increase in viscosity were found to be in agreement with the second break of the I1/I3(logCT curve, and therefore strongly supports the above conclusion.5) The rheological properties of the aqueous mixture of C12-3-C12(2Br/SDS were investigated. All systems exhibit as the Newtonian fluid at given shear rate. At relative high concentration, the rheological character...
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