Zheng Size, Gissinger Jacob, Hsiao Benjamin S, Wei Tao
Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States.
College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu, Sichuan 610059, P. R. China.
ACS Appl Mater Interfaces. 2024 Nov 27;16(47):65677-65686. doi: 10.1021/acsami.4c16229. Epub 2024 Nov 18.
Polyamide membranes are widely used in reverse osmosis (RO) water treatment, yet the mechanism of interfacial polymerization during membrane formation is not fully understood. In this work, we perform atomistic molecular dynamics simulations to explore the cross-linking of trimesoyl chloride (TMC) and m-phenylenediamine (MPD) monomers at the aqueous-organic interface. Our studies show that the solution interface provides a function of "concentration and dispersion" of monomers for cross-linking. The process starts with rapid cross-linking, followed by slower kinetics. Initially, amphiphilic MPD monomers diffuse in water and accumulate at the solution interface to interact with TMC monomers from the organic phase. As cross-linking progresses, a precross-linked thin film forms, reducing monomer diffusion and reaction rates. However, the structural flexibility of the amphiphilic film, influenced by interfacial fluctuations and mixed interactions with water and the organic solvent at the solution interface, promotes further cross-linking. The solubility of MPD and TMC monomers in different organic solvents (cyclohexane -hexane) affects the cross-linking rate and surface homogeneity, leading to slight variations in the structure and size distribution of subnanopores. Our study of the interfacial polymerization process in explicit solvents is essential for understanding membrane formation in various solvents, which will be crucial for optimal polyamide membrane design.
聚酰胺膜广泛应用于反渗透（RO）水处理中，但膜形成过程中的界面聚合机制尚未完全了解。在这项工作中，我们进行了原子分子动力学模拟，以探索均苯三甲酰氯（TMC）和间苯二胺（MPD）单体在水-有机界面处的交联情况。我们的研究表明，溶液界面为交联提供了单体“浓缩和分散”的功能。该过程始于快速交联，随后动力学变慢。最初，两亲性MPD单体在水中扩散并在溶液界面处积累，与有机相中的TMC单体相互作用。随着交联的进行，形成了预交联的薄膜，降低了单体的扩散和反应速率。然而，受界面波动以及与溶液界面处水和有机溶剂的混合相互作用影响，两亲性薄膜的结构灵活性促进了进一步的交联。MPD和TMC单体在不同有机溶剂（环己烷-己烷）中的溶解度会影响交联速率和表面均匀性，导致亚纳米孔的结构和尺寸分布略有变化。我们在明确溶剂中对界面聚合过程的研究对于理解各种溶剂中的膜形成至关重要，这对于优化聚酰胺膜设计至关重要。
