Hu Song-Shuang, Zhou Zhao-Hui, Zhang Lei, Xu Zhi-Cheng, Gong Qing-Tao, Jin Zhi-Qiang, Zhang Lu, Zhao Sui
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.
Soft Matter. 2015 Oct 28;11(40):7960-8. doi: 10.1039/c5sm01855b. Epub 2015 Sep 1.
The contact angle measurements for the aqueous solutions of two pairs of zwitterions on quartz surfaces have been investigated by the sessile drop analysis. The different physicochemical parameters such as the critical micelle concentration (CMC), surface tension, contact angle, surface excess on air-liquid and solid-liquid interfaces and work of adhesion have been estimated. The obtained results show that the contact angle of surfactants such as alkyl carboxylbetaine (ACB) and ditolyl substituted alkyl carboxylbetaine (BCB) remains almost constant in a wide range of surfactant concentration and increases gradually above CMC, which are quite different from traditional surfactants reported in the literature. Surfactants with bigger polar groups have a more steric effect on the quartz surface and the contact angle remains relatively unchanged. Moreover, an increase in quartz-liquid interfacial tension (γSL) has been observed due to the adsorption of four zwitterionic surfactants. Especially for ACB and BCB, at the surfactant concentrations higher than 5 × 10(-5) mol L(-1), a moderate increase in the interfacial tension of the quartz-liquid is observed, which suggests that ACB and BCB can form a saturated adsorption film briefly on the quartz surface and then adsorb again. However, the addition of alkyl sulfobetaine (ASB) and ditolyl substituted alkyl sulfobetaine (BSB) after CMC cannot adsorb on the quartz surface again due to the steric effect of bigger polar groups.
通过静滴分析研究了两对两性离子水溶液在石英表面的接触角测量。估算了不同的物理化学参数，如临界胶束浓度（CMC）、表面张力、接触角、气液和固液界面的表面过剩以及粘附功。所得结果表明，烷基羧基甜菜碱（ACB）和二芳基取代烷基羧基甜菜碱（BCB）等表面活性剂的接触角在很宽的表面活性剂浓度范围内几乎保持恒定，并且在高于CMC时逐渐增加，这与文献中报道的传统表面活性剂有很大不同。具有较大极性基团的表面活性剂对石英表面有更大的空间效应，接触角保持相对不变。此外，由于四种两性离子表面活性剂的吸附，观察到石英 - 液体界面张力（γSL）增加。特别是对于ACB和BCB，在表面活性剂浓度高于5×10（-5）mol L（-1）时，观察到石英 - 液体的界面张力有适度增加，这表明ACB和BCB可以在石英表面短暂形成饱和吸附膜，然后再次吸附。然而，在CMC之后添加烷基磺基甜菜碱（ASB）和二芳基取代烷基磺基甜菜碱（BSB）由于较大极性基团的空间效应不能再次吸附在石英表面。
