Biofouling-resistance control of expanded poly(tetrafluoroethylene) membrane via atmospheric plasma-induced surface PEGylation

• Original study of ePTFE membranes with controllable and efficient surface PEGylation.
• Facile approach of surface PEGylation via atmospheric plasma-induced modification.
• Well-controlled grafting quality of PEGylated layer on chemical-inert ePTFE membranes.
• New physical insights of anti-bacterial performance correlated with protein resistance.
• Correlation between biofouling resistance and hydration capability of ePTFE membranes.

In this work, the research focus is laid on the preparation of biofouling-resistant expanded poly(tetrafluoroethylene) (ePTFE) membranes via a facile process of atmospheric plasma-induced surface PEGylation. After surface coating of poly(ethylene glycol) methyl ether methacrylate (PEGMA), plasma-induced copolymerization was performed by a new atmospheric plasma treatment process over a short period ranging from 0 to 120 s. Controllable grafting and growth of PEGylated copolymer segments with treatment time was ascertained by FT-IR, contact angle, surface roughness, and grafting yield analysis. The grafting yield was enhanced with the plasma treatment duration, evidencing a very good process control. The surface roughness increased until a 60 s treatment time, before decreasing owed to saturation of surfaces with grafted copolymer and the obtaining of homogeneous PEGylated layer. The water contact angle dropped from 105±1° for the virgin membrane to 9±1° for the PEGylated ePTFE membrane obtained at a 120 s plasma treatment, evidencing superhydrophilic surfaces. The PEGylated ePTFE membranes effectively reduced the adsorption of fibrinogen, a sticky protein, up to 18% the limitation of the virgin membrane. Bacterial attachment owed to Gram-positive bacteria (Staphylococcus epidermidis) and Gram-negative bacteria (Escherichia coli) was also effectively inhibited even after a 24 h incubation time from a 60 s treatment time, corresponding to a grafting yield of 0.10 mg/cm2. This work suggests that the anti-baterial ePTFE membranes grafted with PEGylated layer in sufficient surface coverage, high hydration capability, and efficient grafting time via atmospheric plasma treatment present potential for use in membrane bioreactor applications, for which biofouling is a major issue.

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