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合成出具有不同头基尺寸的季铵盐Gemini表面活性剂C12(n)-4-C12(n)·2Br(n=1,2,3时分别对应甲基、乙基和丙基,即四亚甲基-α,ω-二(十二烷基二甲(乙、丙)基溴化铵)).以稀释法研究C12(n)-4-C12(n)·2Br在庚烷中形成的W/O微乳的组成和结构.结果表明,庚烷溶液中的部分己醇参与构成混合界面膜,从而改善了混合组分的分子几何形状,生成了稳定的W/O微乳.随着水含量W0增大,微乳的水核也随之增大,变小的界面曲率减小了混合膜对己醇量的需求.增大C12(n)-4-C12(n)·2Br头基尺寸,界面层中己醇与表面活性剂的摩尔比(a)先增大(n从1到2)然后再减小(n从2到3).W0愈大,a在n从2到3时减小得愈明显.在W0=10和20时,微乳水核半径Rw随n增大而减小;但在W0=30时,当n从2到3,Rw反倒明显增大.这些结果表明,季铵头基相连的两个丙基其行为与相连两个甲基或两个乙基时不同,这两个丙基弯曲朝向庚烷,撑大了表面活性剂烷烃链区域的体积,致使混合界面膜上己醇分子的需求量减少,有助于形成较大尺寸的水核.
The quaternary ammonium salt Gemini surfactant C12 (n) -4-C12 (n) · 2Br with different headgroup sizes was synthesized, which corresponded to methyl, ethyl and propyl, Methylene-α, ω-bis (dodecyldimethyl (ethanepropyl) ammonium bromide).) C12 (n) -4-C12 (n) · 2Br was studied by dilution method in heptane Of W / O microemulsion.The results show that part of hexanol in heptane solution is involved in the formation of mixed interfacial membrane, which improves the molecular geometry of the mixed components and produces a stable W / O microemulsion. With the increase of water content W0, the water core of microemulsion also increases, the smaller the interface curvature reduces the demand for hexanol content of the mixed membrane.C12 (n) -4-C12 (n) · 2Br The head group size, the molar ratio of hexanol to surfactant in the interfacial layer (a) increases first (n from 1 to 2) and then decreases (n from 2 to 3) And the more obvious the decrease was at 3. When W0 = 10 and 20, the radius Rw of microemulsion water nucleus decreased with increasing n, but at W0 = 30, Rw increased significantly when n was from 2 to 3 These results indicate that the two propyl groups attached to the quaternary ammonium headgroup behave differently than if two methyl groups or two ethyl groups are attached, the two propyl groups curving toward the heptane, enlarging the surface Volume alkyl chain region agent, resulting in demand for hybrid molecule hexanol film interface is reduced, the water contributes to the formation of nuclei larger size.