Graphene oxide-graft-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 were 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 via click chemistry. This study systematically investigates the effects of GO-g-PDMA loading on substrate morphology, polyamide (PA) active layer formation, and overall membrane performance. Compared to bare 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 for enhancing FO membrane performance through synergistic improvements in the structure and function.