Graphene Oxide-Grafted Poly(2-(dimethylamino)ethyl methacrylate) as a Functional Additive for Structurally Tuned and High Performance Thin-Film Composite Membranes

Abstract

Forward osmosis (FO), a pressure-free membrane process, holds significant promise for water purification and seawater desalination. However, its efficiency is often limited by internal concentration polarization (ICP). To address this challenge, high-performance thin-film nanocomposite (TFN) membranes are developed by modifying poly(ethersulfone) (PES) substrates with varying amounts of graphene oxide-graft-poly(2-dimethylaminoethyl methacrylate) (GO-g-PDMA) nanoplates. The PDMA polymer is synthesized via atom transfer radical polymerization (ATRP) and covalently grafted onto azide-functionalized GO using a click chemistry approach. This study systematically investigates the effects of GO-g-PDMA functionalization and loading on substrate morphology, polyamide (PA) active layer formation, and overall membrane performance. Compared to non-functionalized GO, GO-g-PDMA significantly enhances the PES substrate’s hydrophilicity, porosity, and water permeability. The optimally loaded TFN membrane (0.5 wt.% GO-g-PDMA) exhibits superior FO performance, achieving water fluxes of 27.8 ± 1.9 L·m⁻²·h⁻¹ (LMH) in FO mode and 52.1 ± 1.5 LMH in PRO mode. Importantly, this membrane also demonstrates a 53.4% reduction in the structural parameter (S) relative to the unmodified TFC membrane, underscoring its improved resistance to ICP. These findings highlight the potential of GO-g-PDMA-functionalized substrates in advancing FO membrane technology through synergistic enhancements in structure and function.