Lv Wei-Feng, Zhou Zhao-Hui, Zhang Qun, Luo Wen-Li, Wang Hong-Zhuang, Ma De-Sheng, Zhang Lei, Wang Rong, Zhang Lu
Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, P. R. China.
Soft Matter. 2019 Aug 21;15(33):6725-6731. doi: 10.1039/c9sm01086f.
The adsorption of xylyl-substituted biquaternary ammonium salt Gemini surfactants with different spacer (C3 and C6) at polytetrafluoroethylene (PTFE) and polymethylmethacrylate (PMMA) surfaces has been investigated and the different adsorption parameters such as surface tension, contact angle, adhesional tension, solid-water interfacial tension and work of adhesion have been estimated. The results show that C3 and C6 have similar adsorption behaviors at PTFE and PMMA surfaces. C3 and C6 adsorb gradually at a PFTE-water interface via hydrophobic interactions and the adsorption amounts at the water-air interface are almost three times higher than those at the PTFE-water interface due to the steric hindrance effect. However, the contact angle keeps constant throughout the experimental concentration range because the decrease in surface tension just counterbalances the decrease in PFTE-water interfacial tension. On the other hand, C3 and C6 adsorb at the PMMA surface via polar interactions between xylyl and functional groups of PMMA before CMC. Similar to PTFE, the increase in PMMA-water interfacial tension compensates the decrease in surface tension and the contact angle also shows a stationary value before the CMC. A bi-layer structure of C3 and C6 will be formed at the PMMA-water interface via hydrophobic interaction and PMMA-water interfacial tension decreases consequently after the CMC, which results in the decrease in contact angle.
研究了具有不同间隔基（C3和C6）的二甲苯基取代双季铵盐Gemini表面活性剂在聚四氟乙烯（PTFE）和聚甲基丙烯酸甲酯（PMMA）表面的吸附情况，并估算了不同的吸附参数，如表面张力、接触角、粘附张力、固-水界面张力和粘附功。结果表明，C3和C6在PTFE和PMMA表面具有相似的吸附行为。C3和C6通过疏水相互作用在PFTE-水界面逐渐吸附，由于空间位阻效应，在水-空气界面的吸附量几乎比在PTFE-水界面高3倍。然而，在整个实验浓度范围内接触角保持恒定，因为表面张力的降低正好抵消了PFTE-水界面张力的降低。另一方面，在临界胶束浓度（CMC）之前，C3和C6通过二甲苯基与PMMA官能团之间的极性相互作用吸附在PMMA表面。与PTFE类似，PMMA-水界面张力的增加补偿了表面张力的降低，并且在CMC之前接触角也显示出一个稳定值。在CMC之后，C3和C6将通过疏水相互作用在PMMA-水界面形成双层结构，从而导致PMMA-水界面张力降低，进而导致接触角减小。
