Document Type
Article
Publication Date
5-20-2025
Abstract
For nearly 30 years, UV-induced free radical polymerization has been used to modify the surface chemistry of polyethersulfone (PES) membranes, films, and coatings. The initial mechanism for the grafting process was introduced in the 1990s and supported without direct evidence of covalent bond formation. Since then, claims of ‘grafting from’ membranes in the literature rely on similar evidence using a combination of gravimetry, attenuated total reflectance infrared spectroscopy, contact angle goniometry, water sorption, and/or water permeance. While these techniques provide evidence of the presence of a polymer coating, they do not provide direct evidence of covalent bond formation between the grafted polymer and the PES membrane or support. Thus, it is possible to mischaracterize a physisorbed film as a chemically bonded grafted polymer. We use experimental data from a model system to examine two key areas: 1) the impact of experimental parameters (UV intensity, UV wavelength, grafting time, and monomer concentration) on the degree of grafting and 2) the limitations of the current literature-accepted techniques used to characterize surfaces functionalized by UV-grafting. NMR is introduced as a technique to quantitatively analyze grafting from a PES membrane and is compared directly to the literature-accepted techniques to expose ‘false positives’ that may lead to incorrect conclusions about ‘grafting from’. Finally, we use 2D NMR techniques to present direct evidence of covalent bond formation from the UV-initiated reaction between a model PES monomer and a model methacrylate monomer in solution.
Keywords
fouling resistance, functional membrane, membrane adsorber, surface modification
Language
English
Publication Title
Journal of Membrane Science
Grant
DE-SC0021260
Rights
© 2025 The Author(s). This is an Open Access work distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Suresh, P., Sibley, M. M., Che, A. C., Ward, L. M., Weinman, S. T., & Duval, C. E. (2025). Functionalizing polyethersulfone membranes: using NMR to avoid pitfalls when using UV-induced polymerization to'graft from'surfaces. Journal of Membrane Science, 124243.
Manuscript Version
Final Publisher Version