Interfacial rheology for physics-based structuring of polyamide desalination membranes

Abstract

Fluid interfaces with dynamic composition and microstructures exhibit complex rheological behavior, which plays a crucial role in various chemical and biological processes, including stabilizing emulsions and foams and facilitating vital respiratory activities. The study reveals the critical influence of this two-dimensional rheology in governing the dynamics of interfacial polymerization—the gold standard method for fabricating state-of-the-art polyamide (PA) desalination membranes. Here, by leveraging photoreactive amphiphiles to precisely tune the interfacial rheology at the water–oil interface, we achieve control over patterned fluid instabilities during interfacial polymerization and, correspondingly, the membrane surface morphology. The resulting PA membranes exhibit macroscopically uniform hollow-ridged structures with length scales strongly correlated with effective interfacial viscosity. Consequently, these PA membranes exhibit high nanofiltration performance, achieving up to 99.8% Na2SO4 rejection with a water permeance of 44.15 l m−2 h−1 bar−1. Importantly, we demonstrate the scalability of this approach through module-scale membrane fabrication with consistent performance. This physics-based approach to regulating interfacial rheology represents an important advancement in controlled membrane fabrication for sustainable water purification. This study quantifies how interfacial mechanics govern interfacial polymerization. Using photoreactive amphiphiles to precisely tune two-dimensional rheology at the water–oil interface, this approach links interfacial viscosity to the instability-selected length scale of hollow-ridged polyamide morphology, establishing a physics-based route to scalable, high-performance polyamide membranes.