Multilayering of Calcium Aerosol-OT at the Mica/Water Interface Studied with Neutron Reflection: Formation of a Condensed Lamellar Phase at the CMC
Multilayering of Calcium Aerosol-OT at the Mica/Water Interface Studied with Neutron Reflection: Formation of a Condensed Lamellar Phase at the CMC
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DOI：
10.1021/acs.langmuir.6b03601
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发表时间：
2016-12-13
期刊：
影响因子：
3.9
通讯作者：
Clarke, S. M.
中科院分区：
文献类型：
--
作者：
Griffin, L. R.;Browning, K. L.;Clarke, S. M.
采用镜面中子反射法，研究了表面活性剂二（2-乙基己基）琥珀酸磺酯（AOT）在浓度为0.1 ~ 2 CMC的云母/水界面上对钠盐和钙盐的吸附。探讨了吸附的pH依赖性。即使在临界胶束浓度（CMC）下，也没有发现Na（AOT）吸附的证据，而在0.5 CMC及以上的浓度下，钙盐被发现有明显的吸附。这一有趣而有些出乎意料的发现表明，反离子同一性可以用来调节阴离子表面活性剂在阴离子表面上的吸附。在CMC上，在pH为7和9时吸附了3层缩合的Ca(AOT)(2)，在pH为4时吸附了4层缩合的Ca(AOT)(2)。在云母表面Ca(AOT)(2) CMC处的多层是这种表面活性剂/表面组合的一个不寻常的特征。在CMC的其他表面只观察到单双层吸附。我们认为这是由于云母的高电荷密度必须为表面活性剂提供一个很好的模板。
Using specular neutron reflection, the adsorption of sodium and calcium salts of the surfactant bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT or AOT) has been studied at the mica/water interface at concentrations between 0.1 and 2 CMC. The pH dependence of the adsorption was also probed. No evidence of the adsorption of Na(AOT) was found even at the critical micelle concentration (CMC) while the calcium salt was found to adsorb significantly at concentrations of 0.5 CMC and above. This interesting and somewhat unexpected finding demonstrates that counterion identity may be used to tune the adsorption of anionic surfactants on anionic surfaces. At the CMC, three condensed bilayers of Ca(AOT)(2) were adsorbed at pH 7 and 9 and four bilayers adsorbed at pH 4. Multilayering at the CMC of Ca(AOT)(2) on the mica surface is an unusual feature of this surfactant/surface combination. Only single bilayer adsorption has been observed at other surfaces at the CMC. We suggest this arises from the high charge density of mica which must provide an excellent template for the surfactant.