Electrostatic-modulated interfacial polymerization toward ultra-permselective nanofiltration membranes

Abstract

Summary Interfacial polymerization (IP) is a platform technology for ultrathin membranes. However, most efforts in regulating the IP process have been focused on short-range H-bond interaction, often leading to low-permselective membranes. Herein, we report an electrostatic-modulated interfacial polymerization (eIP) via supercharged phosphate-rich substrates toward ultra-permselective polyamide membranes. Phytate, a natural strongly charged organophosphate, confers high-density long-range electrostatic attraction to aqueous monomers and affords tunable charge density by flexible metal-organophosphate coordination. The electrostatic attraction spatially enriches amine monomers and temporally decelerates their diffusion into organic phase to be polymerized with acyl chloride monomers, triggering membrane sealing and inhibiting membrane growth, thus generating polyamide membranes with reduced thickness and enhanced cross-linking. The optimized nearly 10-nm-thick and highly cross-linked polyamide membrane displays superior water permeance and ionic selectivity. This eIP approach is applicable to the majority of conventional IP processes and can be extended to fabricate a variety of advanced membranes from polymers, supermolecules, and organic framework materials.

Nanofiltration Membranes with Crumpled Polyamide Films: A Critical Review on Mechanisms, Performances, and Environmental Applications

“…In addition to increased membrane surface area, the formation of crumpled morphology is often accompanied by the reduced intrinsic thickness of polyamide layers (Figure b2), ,− which is possibly ascribed to the changes in interfacial polymerization reaction (see the section “Interfacial Instability”) such as inhibited amine monomer diffusion and facilitated polyamide film formation. This reduced thickness of the rejection layer, in some cases up to ∼6 times, also favors an improved water permeance of crumpled NF membranes (Figure b2).…”

Polyamide membranes enabled by covalent organic framework nanofibers for efficient reverse osmosis

“…During the interfacial polymerization, TpPa nanofibers with large surface area and well‐defined micropores can effectively adsorb MPD solution. This would slow the diffusion of MPD toward the organic solution to react with TMC 43,44 . Therefore, after the incorporation of TpPa nanofibers, the fast interfacial reaction can be controlled to some extent.…”

Ultrathin Membranes for Separations: A New Era Driven by Advanced Nanotechnology

“…[ 9 ] Copyright 2015, Science (AAAS); c) electrostatic‐modulated interfacial polymerization (eIP); Reproduced with permission. [ 130 ] Copyright 2021, Elsevier; d) IP process at a free aqueous–organic interface; Reproduced with permission. [ 131 ] Copyright 2017, Elsevier.…”

“…[104] Recently, You et al proposed an electrostatic-modulated IP (eIP) toward the controllable fabrication of ultra-permselective PA membranes. [130] Phytate, a natural organophosphate bearing high charge density is coordinatively anchored onto a porous ultrafiltration membrane as a supercharged substrate. The phytate-coordinated substrate simultaneously enriches amine monomers and decelerates their diffusion rate via high-density long-range electrostatic attraction, generating nearly-10-nm highly-crosslinked PA membranes with outstanding NF performance (Figure 6c).…”