Effect of branching in zwitterionic polymer brushes grafted from PES UF membrane surfaces via AGET-ATR(c)P

Abstract

This research explored the relationship between the antifouling behavior of porous ultrafiltration (UF) membranes and linear or branched brushes adorning their surfaces. Polyethersulfone UF membranes were functionalized via one-pot lithiation/acylation to enable surface-initiated activators generated by electron transfer for atom transfer radical (co)polymerization of sulfobetaine methacrylate (SBMA) and N,N′-methylenebisacrylamide (MBAm). Changing the SBMA/MBAm ratio and polymerization time grafted brushes at different branching and thicknesses. Surface analyses verified differences in brush architecture and that the degree of grafting increased with grafting time – it was higher for linear brushes than branched ones. Colloidal probe lateral force atomic force microscopy (LFM) showed ideal hydration–lubrication propensity of the lower branching degree poly(SBMA-co-MBAm) over pristine, linear poly(SBMA), and higher branching poly(SBMA-co-MBAm)-grafted membranes. Sharp-tip LFM predicted a critical size of <15 nm for penetrating the branched brush layers. Fouling experiments with bovine serum albumin (∼10 nm) and dextran (∼18 nm) revealed that linear and branched modifications had significantly less fouling than the pristine membrane. An optimal degree of branching can limit foulant adsorption, but fouling could be enhanced if the polymers' hydration capacity was diminished relative to a less dense network. Fouling experiments with soluble microbial products further demonstrated the branched membrane's high antifouling activity.