Over the past several decades, UV-curing has given rise to new functional materials in various ﬁelds of polymer science. The attraction of photopolymerization stems from the excellent control over the spatial and temporal polymerization process, along with high cross-linking densities and low energy cost. To broaden the scope of potential applications for this technique, there is a need to introduce new polymers with unconventional functionality for the growing demand in industry. Polyelectrolytes have been filling a niche in polymer science as they have noticeable differences in their chemical and physical properties as compared to neutral polymers. This includes their conformation in solution, the propensity to form gels, and the potential to form layer-by-layer architectures on a surface. Bringing polyelectrolyte chemistry and photopolymerization together represents a paradigm shift in what may lead to new functional materials.
Researchers at Western University have developed a family of new electrolyte monomers containing phosphonium or borate salts with a wide variety of substituents. These monomers can be photopolymerized in the presence of a chemical crosslinker and produce covalently crosslinked polymer networks. These crosslinked networks can be formed into thin films and coat surfaces if desired. It is also possible to obtain thin films with high water repellency (having a water contact angle greater than 150°) by varying both the counter ion (of the phosphonium or borate) and the hydrophobicity of the substituents (incorporating fluorinated groups). A wide variety of monomers have been developed leading to the vast landscape of applications for these materials.
Cuthbert, T. J.; Guterman, R.; Ragogna, P. J.; Gillies, E. R. Contact Active Antibacterial Phosphonium Coatings Cured with UV Light. Journal of Materials Chemistry B 2015, 3 (8), 1474–1478. https:/doi.org/10.1039/C4TB01857E.
Berven, B. M.; Oviasuyi, R. O.; Klassen, R. J.; Idacavage, M.; Gillies, E. R.; Ragogna, P. J. Self-Crosslinking Borate Anions for the Production of Tough UV-Cured Polyelectrolyte Surfaces. Journal of Polymer Science Part A: Polymer Chemistry 2012, 51 (3), 499–508. https:/doi.org/10.1002/pola.26388.
Guterman, R.; Hesari, M.; Ragogna, P. J.; Workentin, M. S. Anion-Exchange Reactions on a Robust Phosphonium Photopolymer for the Controlled Deposition of Ionic Gold Nanoclusters. Langmuir 2013, 29 (21), 6460–6466. https:/doi.org/10.1021/la400516v.
The UV curing time occurs within a second (and solvent free), in comparison to thermal curing which can be long and energy intensive.
It is anticipated that these polymer networks can be formed by a roll-to-roll polymer production process. Wide variety of monomers and crosslinkers available to tailor the material formed to the users needs.
- Gas Barrier Properties: The deposition of several polymer network-clay bilayers led to ﬁlms with gas barrier properties that surpass industry requirements.
- Anion/ Cation Exchange membranes: When cast as a ﬁlm, these networks can exchange their ionically bound electrolytes with free electrolytes. For example, Au-25 nanoparticles were exchanged with a phosphonium counterion to obtain an Au-25 coated polymer. This allows for the manipulation of gold nanoparticles in the solid state.
- Catalysts: A borate anion bearing phosphino ligands was exchanged onto a polymer surface with subsequent formation of a phosphino-palladium complex that had activity as a Suzuki cross-coupling catalyst.
- Antimicrobials: Polymers having different amounts of the ionic salt (phosphonium) were produced and found capable of killing bacteria.
- Licensing Partnerships
- Collaborative Research
United States Issued Patent # 9,481,743