Abstract Interfacial adsorption and bulk micellization of surfactant are common in natural world, and have prominent applications both in production and life. Surfactant molecules circularly flux among solution bulk, interface, and micelle in surfactant solution. Molecular dynamics (MD) simulations are carried out to compare the state of surfactant among solution monomer, interfacial monolayer, and micelle. Surface coverages from extremely dilute adsorption to saturated adsorption are all considered. Using the quasi harmonic approximation method, configurational entropies of N-dodecyl betaine (NDB) in different environments are obtained. The NDB monomers possess the largest freedom owing to spatial and non-aggregated superiorities. Entropy decomposition, including translational, rotational and vibrational entropies, is calculated to give further comparison and analysis. A new Born-Haber cycle is proposed to depict the state of NDB in different environments and to present entropy change of NDB itself in different mass transport processes. In particular, entropy changes of NDB in physical adsorption process below and above critical micelle concentration are obtained. The NDB molecule exhibits entropy decrease in interfacial adsorption, bulk micellization, and the transport of surfactant from micelle to surface layer.

中文翻译：

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通过构型熵探索溶液单体、界面和胶束中 N-十二烷基甜菜碱状态的关系

摘要 表面活性剂的界面吸附和本体胶束化在自然界中很常见，在生产和生活中都有突出的应用。表面活性剂分子在表面活性剂溶液中的溶液本体、界面和胶束之间循环流动。进行分子动力学 (MD) 模拟以比较溶液单体、界面单层和胶束之间表面活性剂的状态。从极稀吸附到饱和吸附的表面覆盖率都被考虑在内。使用准调和近似方法，获得了N-十二烷基甜菜碱（NDB）在不同环境下的构型熵。由于空间和非聚合优势，NDB 单体拥有最大的自由度。熵分解，包括平移、旋转和振动熵，计算以作进一步的比较和分析。提出了一个新的 Born-Haber 循环来描述 NDB 在不同环境中的状态，并呈现 NDB 本身在不同质量传输过程中的熵变化。特别是，获得了低于和高于临界胶束浓度的 NDB 在物理吸附过程中的熵变化。NDB 分子在界面吸附、大量胶束化和表面活性剂从胶束到表面层的传输中表现出熵减少。