(499b) Surface Characterization of Membrane Surfaces Nanostructured with Tethered Hydrophlic Polymers

Membrane surface structuring with end-tethered hydrophilic polymers is an effective approach for reducing the fouling propensity and improving cleaning efficiency of RO and UF membranes. It has been suggested that, in addition to tailoring of surface chemistry, swelling of the polymer surface layer plays a crucial role in surface screening and minimization of foulant attachment. Accordingly, in the present study the impact of solvent conditions (i.e., salinity and pH) on swelling of hydrophilic tethered polymers was investigated focusing on poly(acrylic acid) (PAAc) chains end-grafted onto polysulfone (PSf) membrane. PAAc chains were graft polymerized onto PSf surfaces via atmospheric pressure plasma-induced graft polymerization (APPIGP). Surface topography of the grafted PAAc layers was evaluated in various solvents (i.e., air, deionized water, and saline water). The size of the tethered polymer chains was assessed by determining the rupture length distributions of the tethered polymer chains via single molecule force measurements performed in aqueous solutions of different salinity. Fouling potential of the polymer layers was then evaluated by adhesion force measurements performed with a functionalized colloidal AFM probe. The results of the present study provide a direct measure of the potential effectiveness of tethered chains for membrane fouling reduction. In this regard, direct surface force measurement can guide the optimization of surface structuring with polymer chains for synthesizing high performance low fouling membranes.