Atmospheric pressure plasma - ARGET ATRP modification of poly(ether sulfone) membranes: A combination attack

A novel surface modification technique for grafting alkyl methacrylate monomers from commercial poly(ether sulfone) (PES) nanofiltration membranes is developed through a combination of helium and oxygen atmospheric pressure plasma treatment followed by Activators Regenerated by Electron Transfer (ARGET) Atom Transfer Radical Polymerization (ATRP). The resulting membrane surfaces show degree of grafting increases of 28%, 94%, and 270% for methyl methacrylate (C1), hexyl methacrylate (C6), and stearyl methacrylate (C18), respectively, when characterized with Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy. Scanning Electron Microscopy and Atomic Force Microscopy (AFM) show a rippled, fibrous morphology for the PES membranes grafted with C18 and reinforced through molecular dynamics simulations. AFM of the PES membranes grafted with C18 show an increase of similar to 23% in root-mean square (RMS) roughness as well as 4x higher adhesion force when probed with a hydrophobic gold cantilever tip when compared with the unmodified PES membranes, confirming a successful surface grafting reaction and increase in surface hydrophobicity, respectively. This technique allows enhanced synthesis of polymer grafted membranes using relatively green reaction solvent and enables structure-by-design surface morphology control with future applications in membrane separation processes such as organic solvent nanofiltration, gas separations, and desalination.