一种不对称阴离子Gemini表面活性剂的合成及表面活性研究

以α-溴代十四酸乙酯和4-癸基苯酚为原料,经Williamson醚化、磺化及皂化反应制备了一种不对称阴离子Gemini表面活性剂α-(4-癸基-2-磺基)-苯氧基十四酸钠,简写为C12CO2Na-p-C10SO3Na,考察了醚化反应条件,并用FTIR和1HNMR表征了中间体及目标产物结构。结果表明,醚化反应的最佳条件为:以N,N-二甲基甲酰胺(DMF)和甲苯作溶剂,无水K2CO3作缚酸剂,物料比n(α-溴代十四酸乙酯)∶n(4-癸基苯酚)=1.05∶1,回流反应3 h,醚化产物收率为77.2%(以4-癸基苯酚计)。采用吊片法测定了目标产物的表面活性,其表面张力最低可降至26 mN/m左右,临界胶束浓度(CMC)为3.28×10-6mol/L,比相应常规单链表面活性剂十四烷酸钠和间癸基苯磺酸钠的CMC低3个数量级,体现出Gemini表面活性剂优异的表面活性。

Synthesis and Surface Activity of an Asymmetric Anionic Gemini Surfactant

An asymmetric Gemini surfactant, comprising two nonidentical hydrocarbon chain lengths and two different anionic hydrophilic groups, abbreviated as C12CO2Na-p-C10SO3Na has been synthesized through Williamson etherification, sulfonation and saponification. Ethyl 2-bromomyristate and 4-decylphenol were used as the starting material. The structures of main intermediate products and the title product were characterized by FT-IR and 1H NMR. The optimum conditions for etherification were n (ethyl 2-bromomyristate) : n (4-decylphenol) = 1.05:1, K2CO3 as acid binding agent, DMF and toluene as solvent, and refluxing for 3 h. The yield of ethyl -(4-decyl) phenoxytetradecanoate was 77.2% (basing on 4-decylphenol). The surface activity of C12CO2Na-p-C10SO3Na was measured by Wilhelmy method. The surface tension could decrease to about 26 mN/m, and the critical micelle concentration (CMC) was found to be 3.28×10-6 mol/L. The CMC value was nearly 3 orders of magnitude lower than that of the corresponding traditional surfactants, such as sodium myristate and sodium m-decylbenzene sulfonate. The results illustrated that the asymmetric anionic Gemini surfactant show high surface activity.