三取代直链烷基苯磺酸钠的界面扩张性质

Interfacial Dilational Properties of Tri-Substituted Alkyl Benzene Sulfonates

利用悬挂滴方法研究了五种表面活性剂3,4-二己基苯磺酸钠(66)、3,4-二庚基苯磺酸钠(77)、2-乙基-4,5-二己基苯磺酸钠(266)、2-丙基-4,5-二己基苯磺酸钠(366)和2-丁基-4,5-二己基苯磺酸钠(466)在空气-水和癸烷-水界面上的扩张流变性质,考察了烷基取代在苯环不同位置对分子界面行为的影响.研究发现,苯环不同位置的取代烷基链长变化对扩张弹性模量和扩张粘性模量影响不同.随着烷基链长增长,表面扩张弹性模量均增加,而扩张粘性模量表现则不同:邻位短链烷基碳数从2变化到4,对粘性模量贡献不大;而间位长链烷基增长对表面弛豫过程影响较大,粘性模量明显增大.油分子的插入能大大削弱间位长链烷基间的强相互作用,一方面导致界面弹性模量和粘性模量远低于表面,同时使得同分异构分子77和266的界面扩张粘性模量数值接近.

The dilational rheological properties of five types of surfactants：sodium 3,4-dihexylbenzene sulfonate （66）,sodium 3,4-diheptylbenzene sulfonate （77）,sodium 2-ethyl-4,5-dihexylbenzene sulfonate （266）,sodium 2-propyl4,5-dihexylbenzene sulfonate （366）,and sodium 2-butyl-4,5-dihexylbenzene sulfonate （466） at the air-water and decanewater interfaces were investigated by a drop shape analysis method.The influence of hydrophobic chains located at different positions on the benzene ring on the interfacial molecular behavior was investigated.Experimental results showed that the hydrophobic chains that were located at different positions affected the dilational elasticity and dilational viscosity differently.The dilational elasticity appeared to increase with an increase in the length of the hydrophobic group and the dilational viscosity behaved differently.The short alkyl chain （2-4） ortho to the sulfonate group had little influence on the dilational viscosity,while an increase in the long meta alkyl group played an important role in the surface relaxation process,which resulted in higher surface dilational viscosity.The insertion of decane molecules from the oil phase weakened the strong interactions between the meta-alkyl chains and therefore the interfacial dilational parameters were obviously lower than those of the surface.We also found that the interfacial dilational viscosities of a pair of structural isomers,77 and 266,were approximately equal.