Polymers that respond to pH have gained significant attention as smart coatings and nanoparticles that exhibit adaptative surface properties upon ionization at specific pH conditions. These adaptative films find applications in various fields, such as drug delivery, antifouling surfaces and chemical sensors, where interfacial properties are engineered by tailoring the functionalization of these films.
1,2 Among the synthetic methods used for preparing pH-responsive polymer coatings, atom transfer radical polymerization (ATRP) and reversible addition−fragmentation chain transfer polymerization (RAFT) have been studied extensively, demonstrating high control over the polymerization process when used.
3 Ring-opening metathesis polymerization (ROMP), an alternative polymerization route, offers faster initiation and polymerization rates, high monomer conversion, and narrow molecular weight distribution.
4,5 However, this technique has received less attention due to its limited functional group tolerance and availability of functionalized ROMP monomers.
6 Thus, there is a need for a methodology for fabricating highly tunable pH-responsive polymer films via ROMP to expand its applicability. In this work, we report a facile approach to fabricate pH-responsive copolymer films via surface-initiated ROMP of trans-3,6- endomethylene-1,2,3,6-tetrahydrophthaloyl chloride (NBDAC). These poly(norbornene diacyl chloride) (pNBDAC) films are compositionally versatile due to pendant acyl chloride groups that can react with various alcohols and amines bearing pH-responsive moieties to create films with a wide range of functionality and surface properties. We evaluate the effect of targeted functionalities and their composition on the pH-responsive and electrochemical properties of the films using FTIR spectroscopy, contact angle measurements, and electrochemical impedance spectroscopy. These modified pNBDAC films offer an easy approach to engineering highly tunable pH-responsive coatings and show the potential of ROMP as a viable technique for the design of responsive surfaces.
(1) Maan, A. M. C.; Hofman, A. H.; de Vos, W. M.; Kamperman, M. Recent Developments and Practical Feasibility of Polymer-Based Antifouling Coatings. Advanced Functional Materials 2020, 30 (32), 2000936. https://doi.org/10.1002/adfm.202000936.
(2) Richter, A.; Paschew, G.; Klatt, S.; Lienig, J.; Arndt, K.-F.; Adler, H.-J. P. Review on Hydrogel-Based PH Sensors and Microsensors. Sensors 2008, 8 (1), 561–581. https://doi.org/10.3390/s8010561.
(3) McCormick, C. L.; Kirkland, S. E.; York, A. W. Synthetic Routes to Stimuliâ€Responsive Micelles, Vesicles, and Surfaces via Controlled/Living Radical Polymerization. Journal of Macromolecular Science, Part C 2006, 46 (4), 421–443. https://doi.org/10.1080/15583720600945428.
(4) Choi, T.-L.; Grubbs, R. H. Controlled Living Ring-Opening-Metathesis Polymerization by a Fast-Initiating Ruthenium Catalyst. Angewandte Chemie International Edition 2003, 42 (15), 1743–1746. https://doi.org/10.1002/anie.200250632.
(5) Bielawski, C. W.; Grubbs, R. H. Living Ring-Opening Metathesis Polymerization. Progress in Polymer Science 2007, 32 (1), 1–29. https://doi.org/10.1016/j.progpolymsci.2006.08.006.
(6) Leitgeb, A.; Wappel, J.; Slugovc, C. The ROMP Toolbox Upgraded. Polymer 2010, 51 (14), 2927–2946. https://doi.org/10.1016/j.polymer.2010.05.002.
