Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747AG Groningen, The Netherlands.
Phys Chem Chem Phys. 2010 Oct 14;12(38):12188-97. doi: 10.1039/c0cp00286k. Epub 2010 Aug 16.
The Langmuir-Schaefer (LS) method has been investigated as a means to control the structure of hybrid organoclay thin films consisting of montmorillonite and dimethyldioctadecylammonium (DODA) cations. We observed a significant modification of the compression isotherms as a function of clay mineral concentration in the subphase, implying clay interaction with the alkylammonium monolayer. For a particular range of clay concentrations, LS hybrid monolayers could be readily prepared on a hydrophobic substrate. The structure of hybrid multilayers of DODA and clay platelets, prepared by repeated LS deposition, was found to be governed by the synthetic route: when the multilayer is fabricated by transferring the hybrid Langmuir films from the surface of the clay dispersion, the DODA-clay particles "flip over" while passing through the meniscus during the even cycles of the deposition, as demonstrated from the elemental analysis of the surface by X-ray photoelectron spectroscopy. In our new model for these multilayers, the structural building block consists therefore of two interdigited DODA layers and two clay layers held together by Na(+). Additionally, a minority phase forms, probably differing from the majority one in the conformation of the alkylammonium cations, and can be eliminated by annealing. This deposition procedure leads to a less ordered structure than an alternative route which combines LS deposition and self-assembly to produce a multilayer consisting of two interdigited DODA layers and one clay layer: here the hydrophilic surface of the transferred hybrid Langmuir film is converted to a hydrophobic surface by dipping into a solution of DODA cations before proceeding with the LS deposition of the next layer.
朗缪尔-谢弗（LS）方法已被研究用于控制由蒙脱土和二甲基十八烷基铵（DODA）阳离子组成的混合有机粘土薄膜的结构。我们观察到随着亚相中粘土矿物浓度的变化，压缩等温线发生了显著的变化，这意味着粘土与烷基铵单层相互作用。在特定的粘土浓度范围内，LS 混合单层可以很容易地在疏水性基底上制备。通过重复 LS 沉积制备的 DODA 和粘土片层的混合多层结构，其结构受合成途径的控制：当通过将混合 Langmuir 膜从粘土分散体的表面转移来制备多层时，DODA-粘土颗粒在沉积的偶数循环中通过弯月面时会“翻转”，这可以从 X 射线光电子能谱对表面的元素分析中得到证明。在我们的这些多层结构的新模型中，结构构建块由两个互插的 DODA 层和两个由 Na(+) 结合在一起的粘土层组成。此外，形成了一个次要相，其构象可能与主要相不同，并且可以通过退火去除。与另一种组合 LS 沉积和自组装来制备由两个互插的 DODA 层和一个粘土层组成的多层的替代途径相比，这种沉积程序导致的结构不太有序：在这里，在进行下一层的 LS 沉积之前，通过将混合 Langmuir 膜的亲水表面浸入 DODA 阳离子溶液中，将转移的混合 Langmuir 膜的亲水表面转化为疏水面。
