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Abstract Polyamide thin‐film composite (PA‐TFC) membranes make large‐scale desalination effective. Interfacial polymerization (IP) is used to make PA‐TFC membranes, but it may limit the range of monomers that can be used, which hinders progress toward advanced membranes. Layer‐by‐layer (LbL) sequential deposition could circumvent kinetic and thermodynamic limitations of the conventional IP process to facilitate incorporation of different co‐monomers into the membrane. The selective layer needs to be deposited onto a microporous support, but depositing LbL coatings on microporous supports often results in defective membranes. Using a poly(vinyl alcohol) (PVA) primer between the support and the LbL polyamide layer may prevent defect formation. The water permeance and salt rejection of a three layer, PVA‐primed, LbL‐based PA‐TFC membrane are discussed and compared to a membrane made without the PVA primer and a commercially available membrane. Mass transfer resistances are analyzed using a series resistance model and appear to be small or even negligible compared to that of the polyamide layer. Incorporation of a sulfonated co‐monomer into the polyamide via LbL is reported. The combination of a PVA primer layer and LbL sequential deposition may expand the range of co‐monomers that could be used relative to polyamide membranes prepared by the conventional IP process.
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This content will become publicly available on November 27, 2025
Interfacial Polymerization of Aromatic Polyamide Reverse Osmosis Membranes
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 versus n-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.
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- Award ID(s):
- 2132524
- PAR ID:
- 10626994
- Publisher / Repository:
- ACS
- Date Published:
- Journal Name:
- ACS Applied Materials & Interfaces
- Volume:
- 16
- Issue:
- 47
- ISSN:
- 1944-8244
- Page Range / eLocation ID:
- 65677 to 65686
- Subject(s) / Keyword(s):
- Interfacial Cross-Linking Polymerization Polyamide Membrane Atomistic Molecular Dynamics Simulations' Solvent Effect
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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