阴离子表面活性剂与阳离子表面活性剂的相互作用(Ⅰ)——表面活性

Interactions between anionic surfactants and cationic surfactants(Ⅰ)——Surface activity

通过临界胶束浓度(cmc)、最低表面张力(γcmc)、表面吸附(Γ)、表面膜强度和表面润湿等,介绍了阴/阳离子表面活性剂混合溶液的表面活性。阴/阳离子表面活性剂混合溶液,消除了同电荷之间的斥力,形成了正、负电荷间的引力,十分有利于两种表面活性剂离子间的缔合,同时还增加了疏水性。因此,在适宜条件下,可以使胶团更容易形成,表面(或界面)上吸附量增加,使得复配溶液具有很低的表面和界面张力,提高表面活性。不仅等摩尔比的混合溶液的cmc和γcmc显著下降,非等摩尔混合也使cmc减小、γcmc降低。等摩尔混合溶液表面吸附层分子摩尔比近于1∶1,其他不同比例时,表(界)面层摩尔比在大多数情形中仍接近1∶1。吸咐层呈等比组成时达到最大电性吸引,表(界)面吸附量趋于饱和。与此同时,由于吸附层中分子间静电吸引力的较强相互作用,还使得表面膜机械强度增加,并表现出良好的润湿性能。

The surface activity of mixed anionic surfactants and cationic surfactants has been reviewed by critical micelle concentration （cmc）, surface tension at cmc （γcmc）, surface adsorption, strength of surface membrane （lifetime of air bubbles and heptane droplets）, and wetting power （ contact angle at paraffin surface） and so on. Due to strong electrostatic attraction between the molecules of anionic and cationic surfactants, the aggregations of mixed solution should be much easier than this of single - ionic surfactant solution. At the same time hydropobicity is enhanced. Thus, under suitable conditions, the formation of micelles becomes much easier and the mixtures blend may have higher surface activity. The values of cmc and γcmc of mixed systems were obviously lower than these of single systems not only at 1 ： 1 mole ratio but also at other mole ratios. The mole ratio of the molecules at surface adsorption layer is nearly 1 ： 1 whether the mole ratio of bulk solution at 1 ： 1 or not. Therefore, the surface viscosity, the strength of the surface membranes and the wetting powerability were improved by mixing anionic surfactants and cationic surfactants.