Self-Assembly of Surfactants in Nanopores: A Thermodynamic Study of Confinement and Curvature Effects

本计画旨在探讨非离子型表面活性剂在圆柱形奈米孔洞中聚集吸附时，孔洞的限制与曲率的影响。虽然近年来已经取得了很大的进展，对开放的平面表面上的表面活性剂的自组装的理解，很少有人知道的限制效应和曲率效应的意义上的聚集吸附在狭窄的孔隙。这些问题将通过研究烷基乙氧基化物（CnEn）的吸附来研究。和烷基葡糖苷（CnGx.）在MCM-41和SBA-15型介孔二氧化硅中，不同烷基链长和头基尺寸的表面活性剂构成均匀尺寸（3至12 nm孔径）的圆柱形孔的六方有序阵列。流动吸附微量热法将被用来确定微分摩尔吸光系数和吸附熵的孔隙填充度的函数，从而提供了一个完整的热力学表征的表面活性剂聚集体在孔隙中的状态。此外，色谱脉冲实验将产生一些关于表面活性剂的吸附动力学的信息。实验计划的细节将与该合作项目的两个合作伙伴小组共同计划，其中将通过计算机模拟研究纳米孔中表面活性剂聚集的静态（Gubbins）和动态（Schoen/Klapp）方面。这些模拟研究的结果将为解释该项目的实验结果提供依据。

This project aims at investigating the effects of confinement and curvature on the aggregative adsorption of nonionic surfactants in cylindrical nanopores. Whereas much progress has been made in recent years towards an understanding of the self-assembly of surfactants on open flat surfaces, little is known about confinement effects and the significance of curvature effects on the aggregative adsorption in narrow pores. These questions will be investigated by studying the adsorption of alkyl ethoxylate (CnEn.) and alkyl glucoside (CnGx.) surfactants of different alkyl chain length and head group sizes in MCM-41 and SBA-15 type mesoporous silicas, which constitute hexagonally ordered arrays of cylindrical pores of uniform size (3 to 12 nm pore diameter). Flow adsorption microcalorimetry will be used to determine the differential molar enthalpies and entropies of adsorption as a function of the degree of pore filling, thus providing a full thermodynamic characterization of the state of surfactant aggregates in the pores. In addition, chromatographic pulse experiments will yield some information about the adsorption kinetics of the surfactants. Details of the experimental program will be planned jointly with the two partner groups of this collaborative project, where static (Gubbins) and dynamic (Schoen/Klapp) aspects of surfactant aggregation in nanopores will be studied by computer simulations. The results of these simulation studies will provide a basis for an interpretation of the experimental results of this project.