ISTO, UMR 7327 CNRS-Université d'Orléans, 1A Rue de la Férollerie, 45071 Orléans Cedex 2, France.
CEMHTI CNRS UPR3079, Université d'Orléans , 1D Avenue de la Recherche-Scientifique, 45071 Orléans Cédex 2, France.
Langmuir. 2017 Sep 26;33(38):9759-9771. doi: 10.1021/acs.langmuir.7b01831. Epub 2017 Sep 12.
The aggregation of surfactants on solid surfaces as they are adsorbed from solution is the basis of numerous technological applications such as colloidal stabilization, ore flotation, and floor cleaning. The understanding of both the structure and the dynamics of surfactant aggregates applies to the development of alternative ways of preparing hybrid layered materials. For this purpose, we study the adsorption of the triethylene glycol mono n-decyl ether (CE) nonionic surfactant onto a synthetic montmorillonite (Mt), an aluminosilicate clay mineral for organoclay preparation with important applications in materials sciences, catalysis, wastewater treatment, or as drug delivery. The aggregation mechanisms follow those observed in an analogous natural Mt, with the condensation of CE in a bilayer arrangement once the surfactant self-assembles in a lamellar phase beyond the critical micelle concentration, underlining the importance of the surfactant state in solution. Solid-state H nuclear magnetic resonance (NMR) at fast magic-angle spinning (MAS) and high magnetic field combined withH-C correlation experiments and different types of C NMR experiments selectively probes mobile or rigid moieties of CE in three different aggregate organizations: (i) a lateral monolayer, (ii) a lateral bilayer, and (iii) a normal bilayer. High-resolution H{Al} CP-H-H spin diffusion experiments shed light on the proximities and dynamics of the different fragments and fractions of the intercalated surfactant molecules with respect to the Mt surface. Na and H NMR measurements combined with complementary NMR data, at both molecular and nanometer scales, precisely pointed out the location of the CE ethylene oxide hydrophilic group in close contact with the Mt surface interacting through ion-dipole or van der Waals interactions.
表面活性剂在固体表面上的聚集，是胶体稳定、矿石浮选和地板清洁等众多技术应用的基础。了解表面活性剂聚集物的结构和动力学对于开发替代方法制备混合层状材料具有重要意义。为此，我们研究了三甘醇单正癸醚（CE）非离子表面活性剂在合成蒙脱石（Mt）上的吸附，蒙脱石是一种铝硅酸盐粘土矿物，在材料科学、催化、废水处理或药物输送等领域有重要的应用。聚集机制与在类似的天然 Mt 中观察到的机制相同，一旦表面活性剂在层状相中自组装超过临界胶束浓度，CE 就会在双层排列中缩合，这强调了表面活性剂在溶液中的状态的重要性。高磁场下的快速魔角旋转（MAS）固态 H 核磁共振（NMR）结合 H-C 相关实验和不同类型的 C NMR 实验，可选择性地探测三种不同聚集态中 CE 的可移动或刚性部分：（i）横向单层、（ii）横向双层和（iii）正常双层。高分辨率 H{Al} CP-H-H 自旋扩散实验揭示了不同片段和插层表面活性剂分子之间的接近度和动力学。Na 和 H NMR 测量与补充 NMR 数据相结合，从分子和纳米尺度上，精确地指出了 CE 乙氧基亲水基团在与 Mt 表面紧密接触的位置，通过离子偶极或范德华相互作用进行相互作用。
