Comparison of the L-B-L technique with interfacial polymerization and phase inversion: A review

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The demand for energy-efficient purification and desalination applications drives membrane-based separation processes. The performance of a membrane, defined by its permeability, selectivity, mechanical stability, and antifouling properties, is intrinsically linked to the fabrication technique employed. This review critically examines three dominant fabrication paradigms: Phase Inversion (PI), Interfacial Polymerization (IP), and Layer-by-Layer (LbL) Assembly. The mechanisms, historical evolution, and recent innovations for each technique, focusing on their selectivity and permeability, were synthesized. A comparative analysis is presented regarding film thickness control, scalability, material diversity, and environmental footprint. While PI is widely utilized for the formation of asymmetric porous membranes, the immersion precipitation technique is the most widely applied at the industrial level. IP is the gold standard for ultrathin polyamide selective layers in reverse osmosis and nanofiltration processes, making it highly favourable for applications requiring selective permeability. Conversely, LbL has matured from a laboratory curiosity to a scalable platform for highly tailored, multifunctional membranes. LbL assembly stands out for its precision in controlling membrane thickness and properties through the sequential deposition of charged materials. Hybrid fabrication strategies (e.g., LbL on PI supports, IP modifications via aqueous monomers) and the emergence of digital twin technology for process optimization are considered. We conclude that while IP-fabricated membranes currently dominate desalination processes, LbL is rapidly gaining ground due to the adoption of sophisticated processing technologies. Future perspectives, integrating machine learning for recipe prediction and the shift toward green solvents, remain essential for developing the next-generation nanofiltration membranes.