Novel approaches for catalyst recycling in organocatalysis
Final Report Abstract
Within this DFG project, we were able to shed more light on the diffusion processes in PILs-based hydrogels using various macroscopic and microscopic methods. In addition to assigning the transport process to non-Fickian diffusion, we also focused on the degrees of swelling and kinetic considerations of these interesting materials. The influence of the solvent variation, the monomers as well as the crosslinker concentration on the process played a role. The imaging of the diffusion front of water by MRI and the determination of the diffusion coefficients from the different methods completed the picture. In addition, extensive investigations regarding the rheological and mechanical properties were made to better understand the hydrogels behavior. Besides the classical stretch and compression experiments, the shear stress behavior as well as the gelation process were closer investigated. Furthermore, the inherent antibacterial activity towards gram-positive S. aureus as well as against gram-negative P. aeruginosa completed the characterization of these PILs-based hydrogels. As an extra, we extended the scope of all these investigations also to polyelectrolyte-based hydrogels with cationic, anionic, neutral, and zwitterionic backbones. To our knowledge, these extensive screenings of different representatives are not yet described in literature so far. These results are extremely interesting and open up novel applications of these types of hydrogels for example in biomedical applications e.g. for tissue replacement therapy, as implants or for coating implants. In addition, the rheological and mechanical properties in particular are also of great importance for the application of these materials as an immobilization matrix. Other investigations also showed that the production of PILs membranes with a thickness of >1 mm is possible. For PILs, which consist of a combination of poly(VBImBr) and poly(VDodecImBr), we could also demonstrate and publish the reproducible production of thinner PILs-membranes with a thickness of <1 mm. In contrast, the preparation of PILs particles by spray drying is not readily possible. A major challenge in this case is to control the speed of the gelation process. In the field of catalyst recovery, CO2-induced switching for organocatalysts based on primary and tertiary amines has been demonstrated. These findings considerably increase the attractiveness of these catalysts, since they can be easily switched from the organic reaction phase to the aqueous phase by means of CO2 inlet. After a certain regeneration phase or by nitrogen inlet, the catalyst can be switched from the aqueous phase into the fresh organic phase to react again. Unfortunately, due to synthesis problems, the application of CO2 switchable organocatalysts for photocatalysis in the microreactor was not successful so far.
Publications
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Enzyme immobilization in polymerized ionic liquids-based hydrogels for active and reusable biocatalysts. SynOpen 2018, 2(02), 0192-0199
Grollmisch, A., Kragl, U., & Großeheilmann, J.
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Antimicrobial Activity of PILs-based Hydrogels and Their Corresponding Monomers. 5th International Conference on Ionic Liquid-Based Materials (ILMAT V), Paris, France, November 2019
Jastram, A.; Claus, J.; Bucki, R. Janmey, P.A.; Kragl, U.
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Rheological properties of first-generation hydrogels based on ionic liquids. 5th International Conference on Ionic Liquid-Based Materials (ILMAT V), Paris, France, November 2019
Claus, J.; Jastram, A.; Janmey, P.A.; Kragl, U.
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Polymerized ionic liquids-based hydrogels with intrinsic antibacterial activity: Modern weapons against antibiotic-resistant infections. J. Appl. Polym. Sci. 2021, 138(16), 50222
Claus, J., Jastram, A., Piktel, E., Bucki, R., Janmey, P. A., & Kragl, U.
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Rheological properties of hydrogels based on ionic liquids. Polym. Test. 2021, 93, 106943
Jastram, A., Claus, J., Janmey, P. A., & Kragl, U.
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Swelling and Diffusion in Polymerized Ionic Liquids-Based Hydrogels. Polymers 2021, 13(11), 1834
Jastram, A.; Lindner, T.; Luebbert, C.; Sadowski, G.; Kragl, U.
