| In this paper, two series of oligomeric quaternary ammonium salt surfactants (m-2-m type and m-2-m-2-m type, m=12,14,16,18) were prepared through quaternization, using tertiary amine and alkyl bromide as raw materials, isopropanol as solvent. And their surface chemical properties and application properties were also studied.Products of m-2-m and m-2-m-2-m were synthesized by reacting RBr (R=C12H25, C14H29, C16H33, C18H37) with tetramethylethylenediamine or pentamethyldiethylenetriamine respectively. Through measuring yield changed with time, the better reaction time was confirmed as follows: 26～28 h for m-2-m type, while 40～44 h for m-2-m-2-m type, and the yields were all over 75%. The purity was determined by means of the bromphenol blue two-phase titration method to the content of active matter. After purification, the contents of active matter of these products were all beyond 95%. The structures of target products were confirmed by IR, MS and 1HNMR.The surface tensions of aqueous solutions of these surfactants were measured by drop volume method at 45℃. It was found that all of these products had very strong capacities of surface adsorption and micellization. Cmcs of m-2-m type and m-2-m-2-m type were 1.10×10-4～1.03×10-3 mol·L-1 and 4.90×10-5～7.99×10-4mol·L-1;γcmc were 31.39～45.05 mN·m-1 and 37.42～43.96 mN·m-1; C20 were 6.40×10-5～2.96×10-4 mol·L-1 and 8.00×10-6～2.42×10-4 mol·L-1. As the alkyl chain length increased from 12 to 18, cmc and C20 decreased,γcmc increased slightly. Therefore, with the growth of carbon chain length, the tendency to form micelles enhanced, the efficiency of lowering the surface tension increased, and the effectiveness to lower the surface tension decreased. I∞>0, belonged to positive adsorption, which indicated that the concentration of the interface phase was higher than that of the bulk phase. In addition, I∞decreased, while Acmc increased gradually with the growth of alkyl chain length.The results of cmc by three measuring methods, including surface tension method, conductance method and fluorescence probe method, were basically consistent with each other, while the values of cmc by the first two methods were much closer. The cmcs of oligomeric quaternary ammonium salt surfactants were 1～2 orders of magnitude lower than that of conventional surfactant CTAB, so they had higher surface activity.The influence of temperature on the surface chemical property of these surfactants was also investigated. As temperature increased, cmc and Acmc increased,γcmc and C20 as well as I∞declined. The results of thermodynamic calculation indicated that the micellization of oligomeric quaternary ammonium salt surfactants was an entropy-drove spontaneous process, and the temperature raising was beneficial for micellization.The measuring results of foaming property showed that with the increasing of alkyl chain length, foamability weakened, while the stability of foam strengthened gradually. Products of C12 had matchable foamability with DTAB, however, the stability of foam was much stronger. The interactions of these surfactants with two kinds of anionic azo dyes, Methyl Orange (MO) and Congo Red(CR), in aqueous solution were investigated by means of UV-Vis spectroscopy. UV-Vis absorption spectrums of two kinds of dye aqueous solution changed obviously after adding these surfactants. It was observed that the aggregation of the surfactant and dye took place at surfactant concentrations far below the critical micelle concentration of the individual surfactants. The formation of aggregations caused blue shifts with a decrease in the intensity of absorption band. Further increasing of the concentration of surfactant to be higher than the cmc, an absorption spectrum of the dye characteristic in the presence of surfactant micelles happened. The change of the microenvironment led to blue shifts distance decreasing even red shifts appearing, followed by increasing in the intensity of the absorption bands. From the influence of oligomeric quaternary ammonium salt surfactants on the maximum absorption wavelengthλmax and the absorption intensity, it could be concluded that there were strong interactions between these surfactants and two kinds of anionic azo dyes.
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