Oxygen–tolerant photo–SI–ATRP for grafting zwitterionic polymer brushes to ultrafiltration PES membranes

Surface–initiated atom transfer radical polymerization (SI-ATRP) is used to graft polymer brushes onto surfaces to modify their properties. However, its application is limited due to oxygen sensitivity. This research presents a simple oxygen-tolerant SI-ATRP method for grafting polymer brushes onto polyethersulfone ultrafiltration membranes using visible light photo-irradiation with amino-functionalized graphene quantum dots (NH₂-GOQD) as a photo-reducing agent. Irradiating the ATRP solution with NH₂-GOQD, without monomers, for 10 minutes reduced dissolved oxygen to 0.9 mg/mL. Homopolymerization without deoxygenation produces polysulfobetaine (poly(SBMA) with a polydispersity of ∼1.20. Grafting poly(SBMA) onto a membranemimetic surface (polysulfone-coated silicon wafer) or a pristine hard surface (bare silicon wafer) resulted in increased brush thickness with irradiation time, as measured by atomic force microscopy and ellipsometry, respectively. Grafting poly(SBMA) onto PES membranes resulted in rapid modification and a progressive increase in grafting degree. μATR-FTIR analysis confirmed spatially homogeneous grafting. The poly(SBMA)-grafted membranes presented improved physicochemical properties and excellent antifouling performance. Overall, this new approach offers a simple and effective method for polymer brush membrane modification via SI-ATRP.