Influence of pH on the aggregation morphology of a novel surfactant with single hydrocarbon chain and multi-amine headgroups
Influence of pH on the aggregation morphology of a novel surfactant with single hydrocarbon chain and multi-amine headgroups
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DOI：
10.1021/jp075535u
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发表时间：
2008-02-07
影响因子：
3.3
通讯作者：
Jiang, Long
中科院分区：
文献类型：
--
作者：
Wang, Wei;Lu, Wensheng;Jiang, Long
合成了一种新型多胺头基单链表面活性剂双(酰胺乙基-氨基甲酰乙基)十八胺(C18N3)。电子显微研究表明，C18N3在水溶液中在pH 2.0时形成小胶束（直径10-20 nm），在pH 6.8时转变成直径约0.6-2.0 μm的更大的小球囊泡。在 pH 12.0 时，囊泡转变为更大的连续溶致片层结构。当pH = 2时，pH 2下的表面张力（γ）-浓度（C）曲线是普通曲线，在相对较高的表面张力（52 mN m(-1)）下具有2.9 x 10(-1) mol L-1的一个临界胶束浓度。然而，在 pH = 6.8 和 10.5 的 γ-C 图中观察到两个独特的转变点，显示出较高的表面活性，这被认为与胶束-双层结构转变有关。三个胺头基的质子化度 pK(a) 分别为 6.6、10.6 和 10. 9，表明在 pH 2.0 时头基发生完全质子化状态，这与根据吉布斯吸附等温线计算的头基表观表面积一致。不同pH值的水溶液中C18N3的尺寸和形态的变化表明我们的合成表面活性剂作为模板在制造药物递送、生物传感器和生物分子器件方面可能具有巨大的潜在应用。
A novel single-chain surfactant with multi-amine headgroups, bis(amidoethyl-carbamoylethyl) octadecylamine (C18N3), was synthesized. Electronmicrographic study showed that in aqueous solution C18N3 formed small micelles (10-20 nm in diameter) at pH 2.0 and changed into much larger globule vesicles sized about 0.6-2.0 mu m in diameter at pH 6.8. At pH 12.0 vesicles changed to a much larger continued lyotropic lamella structure. At pH = 2, the surface tension (gamma)-concentration (C) curve at pH 2 was an ordinary one, having one critical micelle concentration at 2.9 x 10(-1) mol L-1 at relatively high surface tension (52 mN m(-1)). However, two unique transition points were observed in the gamma-C plot at pH = 6.8 and 10.5, showing higher surface activity that is believed to be associated with the micelle-bilayer structure transition. The protonation degree pK(a)'s of the three amine headgroups, were found to be 6.6, 10.6, and 10. 9, respectively, indicating that a complete protonation state of the headgroups occurred at pH 2.0, which is consistent with the apparent surface areas of headgroup calculated according to Gibbs adsorption isotherm. Variation of sizes and morphologies of C18N3 in aqueous solution at different pH values suggest that our synthetic surfactant may have great potential applications as a template in fabricating drug delivery, biosensors, and biomolecular devices.