Responsive polymer films with dynamic interfacial properties are essential for a wide range of applications, including smart coatings, sensing, and separation membranes.
1–3 In particular, polymer architectures with amphiphilic and pH-sensitive moieties enable dual responsiveness, allowing finely tuned adaptability in chemically diverse environments. While ATRP and RAFT polymerizations have been widely employed for fabricating such films, ring-opening metathesis polymerization (ROMP) remains underutilized despite its rapid kinetics, functional group tolerance, and precise control over molecular architecture.
4,5 The main barriers have been the limited commercial availability of functional monomers that are compatible with the catalyst commonly used in the synthesis. In this work, we introduce a synthetic platform for generating dual-responsive polymer thin films via surface-initiated ROMP (siROMP) of a norbornene diacyl chloride (NBDAC) precursor. This monomer provides a reactive scaffold that can be readily functionalized post-polymerization by reacting with alcohol- or amine-functionalized molecules bearing amphiphilic and pH-responsive groups capable of undergoing reversible reorientation in response to environmental cues. The resulting films exhibit reversible surface reorganization in response to changes in solvent polarity and pH. These films were characterized using FTIR spectroscopy, scanning electron microscopy (SEM), profilometry, electrochemical impedance spectroscopy, and contact angle measurements. pH-switchable wettability was assessed through titration series across acidic and basic conditions, while solvent-responsiveness was evaluated using probe liquids of varying polarity. Wettability studies showed variation in surface free energy depending on the polarity and pH of the contacting medium, consistent with molecular rearrangement at the interface. These interfacial adaptations were quantified using a surface energy calculation model that incorporates conformational changes at the molecular level. Our analysis shows that the polar side chains selectively migrate to the surface under polar solvents or basic conditions, while nonpolar groups dominate the interface in dispersive or acidic environments. This rapid, reversible reorganization enables the films to dynamically adapt their interfacial properties, offering a versatile approach to designing multifunctional polymer surfaces. Overall, this work highlights the potential of ROMP-based systems for developing highly tunable, environmentally responsive coatings.
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(2) Luo, Z.; Xu, Y.; Tian, M.; Gul, Z.; Qiao, B.; Jia, K.; Li, C.; Zhao, C. An Intelligent Solvent-Responsive Surface Molecularly Imprinted Membrane with Switchable Adsorption/Desorption Performance for Selective Separation of Psoralen and Recognition Mechanism. Ind. Crops Prod. 2024, 207, 117766. https://doi.org/10.1016/j.indcrop.2023.117766.
(3) Li, L.; Xu, Z.; Sun, W.; Chen, J.; Dai, C.; Yan, B.; Zeng, H. Bio-Inspired Membrane with Adaptable Wettability for Smart Oil/Water Separation. J. Membr. Sci. 2020, 598, 117661. https://doi.org/10.1016/j.memsci.2019.117661.
(4) Choi, T.-L.; Grubbs, R. H. Controlled Living Ring-Opening-Metathesis Polymerization by a Fast-Initiating Ruthenium Catalyst. Angew. Chem. Int. Ed. 2003, 42 (15), 1743–1746. https://doi.org/10.1002/anie.200250632.
(5) Bielawski, C. W.; Grubbs, R. H. Living Ring-Opening Metathesis Polymerization. Prog. Polym. Sci. 2007, 32 (1), 1–29. https://doi.org/10.1016/j.progpolymsci.2006.08.006.
