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Tuning the surface functionality of polyamide films via termination reaction in molecular layer-by-layer deposition

Published

Author(s)

Christopher Stafford, Yarong Qi, Xun Guan, Yue Zhang, Xitong Liu

Abstract

Molecular layer-by-layer (mLbL) deposition of highly crosslinked polyamide-based membranes affords flexibility and control over membrane properties such as thickness, roughness, and chemistry of the selective membrane layer. Of particular interest is the ability to non-destructively tailor the surface chemistry of the membrane for a particular purpose, such as enhancing hydrophilicity or minimizing membrane fouling. Here, we show that the surface chemistry of the mLbL membrane can be tuned via termination reactions to render the surface rich in -COOH, -NH2, -polyethylene glycol (PEG), or -fluorinated groups. We systematically characterize the resulting surfaces with x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) to validate successful modification and to ensure the low surface roughness is maintained, respectively. We then use pH-dependent contact angle and carboxylate-modified colloidal probe AFM to measure the surface wettability and adhesion of the modified surfaces. The measured adhesion force follows the ranking NH2 ≫ fluorinated > -COOH ≈ PEG, where the -COOH and PEG are repulsive due to charge interactions and hydration state, respectively. Combined with the low surface roughness afforded by mLbL deposition, surface functionalization through termination reactions as shown here will allow researchers to disentangle contributions of surface chemistry from surface roughness to the overall performance and fouling of polyamide-based membranes for water purification and advanced chemical separations.
Citation
Journal of Membrane Science
Volume
661

Keywords

polymer, membranes, deposition, surface chemistry, characterization, adhesion, contact angle

Citation

Stafford, C. , Qi, Y. , Guan, X. , Zhang, Y. and Liu, X. (2022), Tuning the surface functionality of polyamide films via termination reaction in molecular layer-by-layer deposition, Journal of Membrane Science, [online], https://doi.org/10.1016/j.memsci.2022.120855, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=934504 (Accessed March 4, 2024)
Created August 10, 2022, Updated November 29, 2022