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•Polyamide surface nanostructured with a hydrophilic polymer brush layer.•Surface hydrophilicity (or wettability) increased by hydrophilic brush layer.•Increased hydrophilicity with ...both increasing surface roughness and polymer volume.
Surface wettability of terminally anchored hydrophilic polymer brush layers on polyamide–silicon (PA–Si) surfaces was evaluated with respect to surface topography at the nanoscale. Hydrophilic polyvinylpyrrolidone (PVP) and polyacrylamide (PAAm) brush layers were synthesized via graft polymerization onto a PA–Si surface previously activated by surface treatment with atmospheric pressure plasma. Hydrophilicity (or wettability) of the PA substrate, as quantified by the free energy of hydration, was increased upon surface coverage with the PVP and PAAm brush layers by 13–24% (−101.4 to −111.3mJ/m2) and 19–37% (−106.1 to −122.4mJ/m2), respectively. Surface hydrophilicity increased with both increasing surface roughness (0.55–2.89nm and 1.54–5.84nm for PVP and PAAm, respectively) and polymer volume (1.3×106–7.3×106nm3/μm2 and 3.3×106–2.8×107nm3/μm2 for PVP and PAAm surfaces, respectively). The present study suggests that a specific level of surface wettability can be attained by tailor-designing the polymer brush layer’s physicochemical characteristics (e.g., surface roughness, wettability, and polymer water affinity) by adjusting surface topography and surface chemistry, which are controlled by surface activation and polymerization conditions. The above indicates that there is merit in structuring various surfaces with hydrophilic brush layers to increase surface wettability in membrane filtration, biomedical devices, and lubrication applications.
The biofouling propensity and cleaning effectiveness were evaluated for a new generation of polyamide thin-film composite (PA-TFC) membranes that are surface nano-structured (SNS) with terminally ...anchored hydrophilic polymer chains. The SNS-PA-TFC membranes were formed via surface graft polymerization onto the surface of polyamide base membranes previously activated via surface treatment with atmospheric pressure plasma. Poly(methacrylic acid) (PMMA) and polyacrylamide (PAAm) SNS-PA-TFC membranes were synthesized and evaluated with respect to their biofouling resistance using secondary wastewater from a municipal wastewater treatment (MWT) plant. Biofouling resistance and cleaning effectiveness were quantified via flux decline measurements in addition to imaging of the biofouled membranes before and after DI water and chemical (Na2·EDTA) cleaning. Increased biofouling resistance was highest for the PMAA-SNS-PA-TFC membrane being a factor of 4.2 greater than for the commercial membrane of about the same salt rejection used in the MWT plant. Moreover, permeability recovery for the PMAA-SNS-PA-TFC membrane was higher by factors of up to ~1.2 relative to the reference commercial membrane upon cleaning with DI water and more aggressive chemical cleaning at high pressure. The present evaluation of the SNS-PA-TFC membranes suggests that biofouling resistance and cleaning effectiveness of RO membranes can be enhanced via hydrophilic brush layers.
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•RO membrane surface nanostructured with a hydrophilic polymer brush layer.•Reduced membrane biofouling propensity.•Improved membrane cleaning effectiveness.•Increased membrane permeability.
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