Bridging Rigidity and Flexibility: Modulation of Supramolecular Hydrogels by Metal Complexation
Oliver S. Stach, Katharina Breul, Christian M. Berač, Moritz Urschbach, Sebastian Seiffert, Pol Besenius
Abstract
Abstract The combination of complementary, noncovalent interactions is a key principle for the design of multistimuli responsive hydrogels. In this work, an amphiphilic peptide, supramacromolecular hydrogelator which combines metal‐ligand coordination induced gelation and thermoresponsive toughening is reported. Following a modular approach, the incorporation of the triphenylalanine sequence FFF into a structural ( C 3 EG ) and a terpyridine‐functionalized ( C 3 Tpy ) C 3 ‐symmetric monomer enables their statistical copolymerization into self‐assembled, 1D nanorods in water, as investigated by circular dichroism (CD) spectroscopy and transmission electron microscopy (TEM). In the presence of a terpyridine functionalized telechelic polyethylene glycol (PEG) cross‐linker, complex formation upon addition of different transition metal ions (Fe 2+ , Zn 2+ , Ni 2+ ) induces the formation of soft, reversible hydrogels at a solid weight content of 1 wt% as observed by linear shear rheology. The viscoelastic behavior of Fe 2+ and Zn 2+ cross‐linked hydrogels are basically identical, while the most kinetically inert Ni 2+ coordinative bond leads to significantly weaker hydrogels, suggesting that the most dynamic rather than the most thermodynamically stable interaction supports the formation of robust and responsive hydrogel materials.