寡聚度对低聚阳离子季铵盐表面活性剂的聚集行为、油-水界面性能及润湿性的影响

合成了联接基团含有酰胺键及羟基的Gemini阳离子季铵盐表面活性剂Malic 2C12及三聚阳离子季铵盐表面活性剂Citric 3C12，并通过表面张力、电导及动态光散射技术（DLS），研究了Malic 2C12及Citric 3C12的聚集行为。结果表明，随着寡聚度由1（十二烷基三甲基溴化铵，DTAB）增大到2（Malic 2C12）再到3（Citric 3C12），表面活性剂的表面活性提高，临界聚集浓度（CAC）有了数量级的降低，聚集能力大大提高。当浓度高于CAC时，疏水尾链之间的疏水相互作用以及联接基团之间的氢键相互作用促使Malic 2C12聚集形成球形胶束。而3个季铵盐头基间的静电排斥及联接基团的刚性使Citric 3C12以爪状构象存在，聚集形成大聚集体。同时，随寡聚度增大，DTAB、Malic 2C12和Citric 3C12降低油 水界面张力及润湿石蜡表面所需的浓度有数量级的降低。而且，由于爪状构象的Citric 3C12分子之间在大聚集体中相互作用很强，解聚集成单体的过程慢，使得其对石蜡表面的润湿具有时间响应性。

Effect of Degree of Oligomerization on Aggregation Behavior,Oil-Water Interfacial Properties and Wettability of Oligomeric Cationic Quaternary Ammonium Surfactant

The Gemini cationic quaternary ammonium surfactant Malic 2C12 and the trimeric cationic quaternary ammonium surfactant Citric 3C12 were synthesized. The spacer groups of Malic 2C12 and Citric 3C12 bear amide bonds and a hydroxyl group. Their aggregation behaviors were studied by surface tension, electrical conductivity and DLS techniques. With increasing the oligomerization degree from surfactant monomer (DTAB) to dimer (Malic 2C12) and then to trimer (Citric 3C12), the surface activity is enhanced, and the critical aggregation concentration (CAC) decreases systematically by an order of magnitude, the aggregation ability is greatly promoted. Driven by the hydrophobic interaction between hydrophobic chains and the hydrogen bonding between spacer groups, Malic 2C12 aggregates into spherical micelles beyond CAC. Citric 3C12 presents claw like molecular configuration due to the multiple electrostatic repulsion and the rigidity of the spacer group, forming large aggregates beyond CAC. Meanwhile, the surfactant concentration that is required to initiate the reduction of the oil water interfacial tension and the wetting of the paraffin surface decreases by an order of magnitude. Moreover, the wetting of the paraffin surface is time responsive due to the slow dissociation rate of the claw like Citric 3C12 molecules in large aggregates, which should be attributed to the strongest intermolecular interaction in large aggregates.