Zwitterionic Copolymer-Regulated Interfacial Polymerization for Highly Permselective Nanofiltration Membrane
Yuqing Lin, Xuesong Yao, Qin Shen, Takafumi Ueda, Yuki Kawabata, Jumpei Segawa, Kecheng Guan, Titik Istirokhatun, Qiangqiang Song, Tomohisa Yoshioka, Hideto Matsuyama
Abstract
A highly permselective nanofiltration membrane was engineered via zwitterionic copolymer assembly regulated interfacial polymerization (IP). The copolymer was molecularly synthesized using single-step free-radical polymerization between 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-aminoethyl methacrylate hydrochloride (AEMA) (P[MPC-co-AEMA]). The dynamic network of P[MPC-co-AEMA] served as a regulator to precisely control the kinetics of the reaction by decelerating the transport of piperazine toward the water/hexane interface, forming a polyamide (PA) membrane with ultralow thickness of 70 nm, compared to that of the pristine PA (230 nm). Concomitantly, manipulating the phosphate moieties of P[MPC-co-AEMA] integrated into the PA matrix enabled the formation of ridge-shaped nanofilms with loose internal architecture exhibiting enhanced inner-pore interconnectivity. The resultant P[MPC-co-AEMA]-incorporated PA membrane exhibited a high water permeance of 15.7 L·m–2·h–1·bar–1 (more than 3-fold higher than that of the pristine PA [4.4 L·m–2·h–1·bar–1]), high divalent salt rejection of 98.3%, and competitive mono-/divalent ion selectivity of 52.9 among the state-of-the-art desalination membranes.