枝状Gemini咪唑表面活性剂的合成、表征及性能

The synthesis, characterization and properties of branched Gemini imidazolium surfactants

摘要:

为研究枝状连接基对Gemini咪唑表面活性剂性能的影响,以2,2-双(溴甲基)-1,3-丙二醇为连接基合成枝状的Gemini咪唑表面活性剂2,4-二(溴化-3-烷基咪唑)-1,3-丙二醇(［C_n-P-C_n］Br₂),其中n=0,2,14．通过表面张力法和电导法测量其表面活性并计算25 ℃时胶束形成的各项性能参数:临界胶束浓度(ccmc)、表面饱和吸附量(Γcmc)、表面活性剂分子在空气/水界面的最小横截面积(Amin)、效率因子(pC20)和表面压(πcmc)等．结果表明,不同链长的3种表面活性剂具有很高的表面活性,所有表面活性剂胶束形成的吉布斯自由能(ΔG_m)均为负值,说明常温常压下胶束的形成是自发过程．

Abstract:

To study the effect of branched spacer on the property of Gemini imidazolium surfactants, Gemini imidazolium surfactants of 2,4-［bis(3-alkylimidazolium-1-yl) bromide］-1,3-propanediol (［C_n-P-C_n］Br₂, where n is the hydrocarbon chain length of 0,2 or 14) were synthesized with 2,2-dibromomethyl-1,3-propanediol as the spacer. Their surface activity and thermodynamic properties of micellization were characterized by surface tension and electrical conductivity measurements. The values of critical micelle concentration (ccmc), saturation adsorption values at the air/aqueous interface (Γmax), the area per surfactant molecule at the air/aqueous interface (Amin), the efficiency of adsorption (pC20) and surface pressure (πcmc) derived from surface tension measurement at 25 ℃ suggested that the surface activity of ［C_n-P-C_n］Br₂ was high. While Gibbs Free Energy of micellization (ΔGm) of all the surfactants derived from electrical conductivity were all negative, indicating that the formation of micelles was spontaneous.