Comparison of Aggregation Behaviors between Ionic Liquid-Type Imidazolium Gemini Surfactant [C12-4-C12im]Br2 and Its Monomer [C12mim]Br on Silicon Wafer
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- 作者：Mingqi Ao ; Guiying Xu ; Jinyu Pang ; Taotao Zhao
- 刊名：Langmuir
- 出版年：2009
- 出版时间：September 1, 2009
- 年：2009
- 卷：25
- 期：17
- 页码：9721-9727
- 全文大小：1006K
- 年卷期：v.25,no.17(September 1, 2009)
- ISSN：1520-5827
文摘
The aggregation of ionic liquid-type imidazolium gemini surfactant [C12-4-C12im]Br2 on silicon wafer, which is compared with its monomer [C12mim]Br, have been studied. AFM morphology images and contact angle measurements suggest that the aggregations of [C12-4-C12im]Br2 and [C12mim]Br on silicon wafer follow different mechanisms. Below the critical surface aggregation concentrations (CSAC), both surfactant molecules are adsorbed with their hydrophobic tails facing the air. But above the CSAC, [C12-4-C12im]Br2 molecules finally form a bilayer structure with hydrophilic head groups facing the air, whereas [C12mim]Br molecules form a multilayer structure, and with increasing its concentration, the layer numbers increase with the hydrophobic chains and hydrophilic head groups facing the air by turns. Besides, the watery wettability of [C12-4-C12im]Br2-treated silica surface is lower than that of [C12mim]Br at the concentration of 5.0 cmc, and the infrared spectroscopy suggests that the poorer watery wettability of [C12-4-C12im]Br2 may be relative to the less-ordered packing of methylene chains inside the aggregate. These different aggregation behaviors for the two surfactants ascribe to the different molecular structures and electrostatic interactions. This work would have certain theoretical guidance meaning on the modification of solid surface.