Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York (SUNY), Buffalo, New York 14260-4200, United States.
Department of Materials Science and Engineering, University of Utah, 122 S. Central Campus Drive, Room 304, Salt Lake City, Utah 84112, United States.
Langmuir. 2021 May 4;37(17):5339-5347. doi: 10.1021/acs.langmuir.1c00433. Epub 2021 Apr 22.
The self-assembly of surfactants in aqueous solution can be modulated by the presence of additives including urea, which is a well-known protein denaturant and also present in physiological fluids and agricultural runoff. This study addresses the effects of urea on the structure of micelles formed in water by the fluorinated surfactant perfluoro--octanoic acid ammonium salt (PFOA). Analysis of small-angle neutron scattering (SANS) experiments and atomistic molecular dynamics (MD) simulations provide consensus strong evidence for the direct mechanism of urea action on micellization: urea helps solvate the hydrophobic micelle core by localizing at the surface of the core in the place of some water molecules. Consequently, urea decreases electrostatic interactions at the micelle shell, changes the micelle shape from prolate ellipsoid to sphere, and decreases the number of surfactant molecules associating in a micelle. These findings inform the interactions and behavior of surface active per- and polyfluoroalkyl substances (PFAS) released in the aqueous environment and biota.
在水相溶液中，表面活性剂的自组装可以通过添加物（包括尿素）来调节，尿素是一种众所周知的蛋白质变性剂，也存在于生理流体和农业径流中。本研究探讨了尿素对全氟辛酸铵（PFOA）形成的胶束结构的影响。小角中子散射（SANS）实验和原子分子动力学（MD）模拟的分析为尿素对胶束化作用的直接机制提供了有力的证据：尿素通过定位于核心表面的位置取代部分水分子，有助于溶剂化疏水胶束核心。因此，尿素降低了胶束壳的静电相互作用，将胶束形状从扁长椭球体变为球体，并减少了缔合在胶束中的表面活性剂分子的数量。这些发现为了解在水相环境和生物体内释放的表面活性全氟和多氟烷基物质（PFAS）的相互作用和行为提供了信息。
