(399r) Nano-Structuring of UF and RO Membranes with Hydrophilic Polymers – Scalability of Membrane Synthesis Via Atmospheric Pressure Plasma-Induced Graft Polymerization

Surface nano-structuring of membranes with hydrophilic polymer brush layers via atmospheric pressure plasma (APP)-induced graft polymerization (APPIGP) is an effective approach for reducing mineral scaling and biofouling propensity of RO membranes. However, production of large membrane surface area needed for the fabrication of spiral-wound elements requires uniformity of surface activation prior to graft polymerization. Accordingly, in the present study, the application of surface activation by APP, over a large membrane surface area, via a robotic dispensing system was investigated with the goal of optimizing surface activation with respect to the target membrane performance. The plasma treatment time processing conditions were systematically evaluated to arrive at the optimal conditions necessary to achieve uniformity of surface activation. Two different types of APP sources, air and helium-oxygen, were investigated for activating polyamide (PA) based RO and polysulfone (PSf) UF membranes at various plasma operating conditions (i.e., source-substrate distance, plasma exposure time). The optimal plasma operating conditions were quantified via the attainable increase in surface wettability (via contact angel measurements with multiple solvents) which was shown to correlate with the efficiency of subsequent surface graft polymerization. Subsequently, surface graft polymerization was accomplished using a suitable water soluble vinyl monomer to form a polymer brush layer. The uniformity of surface topography was assessed via AFM and XPS analyses, in addition to quantifying membrane permeability and salt rejection. Results of the current study revealed that the APP and graft polymerization conditions can be tailored to provide uniform surface structuring for both RO and UF membranes, which is critical for the scale up of the APPIPG process for producing high performance membranes for water treatment and desalination.