季铵盐型双子表面活性剂在空气-水界面的单分子膜

利用Langmuir膜天平测定不对称双子表面活性剂12-2-16和对称双子表面活性剂12-2-12在空气-水界面上形成单分子膜的表面压,通过单分子膜的π-A等温线、微分等温线和静态弹性,分析其相转变和成膜特性.结果表明,与传统阳离子表面活性剂DTAB比较,12-2-16、12-2-12比DTAB单分子膜的分子极限面积大,崩溃压高,并有较高的静态弹性,因而具有较高的凝聚性和稳定性,其中12-2-16单分子膜的凝聚性和稳定性最高.

Monolayers formed from quaternary ammonium gemini surfactants at air-water interface

Monolayers of a dissymmetric cationic quaternary ammonium gemini surfactant 12-2-16 and a symmetric gemini surfactant 12-2-12 were formed in KSV 2000 Langmuir trough at air-water interface, respectively. The surface pressure of each monolayer was measured using the Wilhelmy plate technique. The features of monolayers at air-water interface were discussed by analyzing the π-A isotherm, the differential curve and the static surface elasticity of monolayers for 12-2-12 and 12-2-16. It was found that such parameters as the molecular limited area, the collapse surface pressure, the static surface elasticities are higher for 12-2-12 and 12-2-16, in comparison with those of a conventional cationic surfactant, dodecyl-trimethylammonium bromide (DTAB). Among the surfactants studied, 12-2-16 monolayer has the highest cohesion and stability.