Research On The Synthesis, Properties And Applications Of Gemini Cationic Surfactants

Gemini surfactant with a molecular structure is a new generation of surfactants, which is made up of two identical amphiphilic moieties covalently connected at the level of the head groups by a spacer group. By this way, the separation between the polar head groups within Gemini surfactants is strongly decreased when they aggregate and thus the surface activity is greatly enhanced.In this paper, through a series of experiments, two series of quaternary-ammonium Gemini surfactants were synthesized. Their critical micelle concentration(cmc ) values, the surface tension at their cmc( r cmc) values , the efficiency of decreasing the surface tension(C2o) , the micelle aggregation number, rheological behavior of Gemini surfactants in aqueous solution, and the thermodynamical properties of micellization were measured. Meanwhile the factors affecting the results were also discussed. The properties of the system of Gemini cationic surfactant/SDS have been investigated, the mole fraction of Gemini component in the mixed micelle and parameters of molecular interaction were calculated. Meanwhile, the applications of Gemini surfactants in industrial energetic materials were deeply studied in details, the actions of Gemini surfactants used as textile auxiliaries were investigated initially. The main results are as follows:1 Two series of quaternary-ammonium Gemini surfactants have been synthesized with their structures testified. The optimized methods of synthesis were determined by discussing the factors affecting reactions.2 Their critical micelle concentration(cmc ) values, the surface tension at their cmc( Y cmc) values and the efficiency of decreasing the surface tension(C2o) of the two series surfactants were measured. Results show that Gemini surfactants have much lower cmc and stronger surface activity comparing with the corresponding common surfactants.3 The excess absorption amount at surface and the area of molecule were discussed. A conclusion can be drawn that the excess absorption amount increases and the area of molecule decreases with the increase of space group carbon number. In the foaming properties of the Gemini surfactants synthesized in this paper, C12-3(OH)-C12 2Cl has shown excellent foaming quality and its foam has the most stable properties.4 The micelle aggregation numbers were measured by the technique time-resolved fluorescence quenching (TRFQ) and fluorescence polarization. The concentration of quaternary-ammonium Gemini surfactants has great influences on the micelle aggregation number. The micelle aggregation number increases with the length of spacer group decreased; and the micelle aggregation number of C12-3(OH)-C12 2Cl is bigger than that of C12-3-C12 2Br.5 The shear rate y was in the range of 0-1875s-1 and the flow behaviors kept Newtonian flow when the concentration of C12-3-C12 2Br and Cu-3(OH)-C12 2Cl separately bellowed 64mmol.L-1 and 54 mmol.L-1. But the flow transformed from Newtonian to non-Newtonian after y reached a value of critical shear rate r*. The viscosity increased with the raise of concentration, and a sharp increase was detected in this region. Little effect on flow behaviors was observed by insertion of -OH into the space group, while increased a little in the same conditions.6 The cmc of Gemini Surfactants increased linearly with the raise of temperature; the trend of micelle formation of the Gemini Surfactants was significantly stronger than the corresponding monomer, and the micellization of the Gemini Surfactants was an entropy-driven process.7 The mixtures of Gemini surfactants and SDS can lower the surface tension of aqueous solutions more effectively, compared with those of the corresponding common surfactants. Their critical micelle concentration (cmc ) values are much smaller than those of mixtures of common surfactants. The interaction parameters between Gemini Surfactants and SDS are far below zero, which indicates a strong molecular interaction.8 Through quantum chemistry, the geometri...