کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1672123 | 1008928 | 2008 | 6 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Effect of the spacer group on the behavior of the cationic Gemini surfactant monolayer at the air/water interface Effect of the spacer group on the behavior of the cationic Gemini surfactant monolayer at the air/water interface](/preview/png/1672123.png)
Surface properties of the insoluble cationic bis-(quaternary ammonium halide) surfactants (Gemini) with polymethylene spacer at the air/water interface were investigated. The monolayers were transferred onto mica by the Langmuir–Blodgett (LB) technique and the corresponding LB films were characterized by the atomic force microscopy (AFM) and the contact angle of water. For the Gemini surfactants with the different spacer length, it was found that the surface pressure-molecular area isotherms resemble to each other. The limiting area increases rapidly and almost linearly with the increase of spacer length for the short spacers, but reaches a maximum at s = 10 and decreases slightly at s > 10. The AFM images show that the surface micelles and the multilayer aggregates gradually appear with the increase of surface pressure. No matter what the surface pressures are, the main structure of the monolayer almost keeps the same, which suggested that the major molecules lie nearly flat on the water surface, while the increase of surface pressure forces the minor alkyl chains to turn only partly or completely vertical to the water surface and even to overturn. This is the cause that the contact angle of water on LB film increases slightly with the surface pressure.
Journal: Thin Solid Films - Volume 516, Issue 23, 1 October 2008, Pages 8782–8787