Fabricating amphiphilic surfaces with enhanced responsive properties and resistance to fouling is crucial for various environmental and clinical applications, including membranes, biological implants, and microfluidics.
1–3 Conventionally, block copolymers are employed for the fabrication of amphiphilic films, which can segregate components at the interface to minimize the interfacial free energy with the surrounding medium.
4 However, since a macromolecular reorganization is required to alter their interfacial composition, these films present a sluggish response. In contrast, amphiphilic monolayers could offer instantaneous molecular reorientation of the terminal groups in response to the polarity of the contacting medium. In this study, we investigate the responsive properties of amphiphilic monolayers when exposed to media of varying polarities. The amphiphilic composition was achieved by functionalizing a preassembled monolayer with commercial molecules containing polar and dispersive functional groups. Since the polarity mismatch of the terminal group influences the surface rearrangement properties, we have screened different chemical compositions and evaluated their responsive surface properties to polar and dispersive probe liquids. For this evaluation, a surface free energy model has been developed in order to estimate the variation in the interfacial free energy that results from the molecular-level surface reorganization induced by the polarity change of the contacting probe liquid. In contrast to other models commonly used for calculating the interfacial free energy of solid surfaces, our model accounts for surface adaptation, enabling the quantification of the resulting change of interfacial energies under environmental stimuli. This evaluation of the terminal group switching has been compared with results from molecular dynamics simulation of these films and complementary experimental characterizations that have helped us determine the chemical composition under different media. In general, our findings provide insights into designing and evaluating the dynamic properties of amphiphilic surfaces with tailored environmental responsiveness.
(1) Trivedi, J. S.; Bera, P.; Bhalani, D. V.; Jewrajka, S. K. In Situ Amphiphilic Modification of Thin Film Composite Membrane for Application in Aqueous and Organic Solvents. Journal of Membrane Science 2021, 626, 119155. https://doi.org/10.1016/j.memsci.2021.119155.
(2) Sun, L.; Guo, J.; Chen, H.; Zhang, D.; Shang, L.; Zhang, B.; Zhao, Y. Tailoring Materials with Specific Wettability in Biomedical Engineering. Advanced Science 2021, 8 (19), 2100126. https://doi.org/10.1002/advs.202100126.
(3) Gokaltun, A. A.; Mazzaferro, L.; Yarmush, M. L.; Usta, O. B.; Asatekin, A. Surface-Segregating Zwitterionic Copolymers to Control Poly(Dimethylsiloxane) Surface Chemistry. J. Mater. Chem. B 2024, 12 (1), 145–157. https://doi.org/10.1039/D3TB02164E.
(4) Luzinov, I.; Minko, S.; Tsukruk, V. V. Adaptive and Responsive Surfaces through Controlled Reorganization of Interfacial Polymer Layers. Progress in Polymer Science 2004, 29 (7), 635–698. https://doi.org/10.1016/j.progpolymsci.2004.03.001.
