Bridging Rigidity and Flexibility: Modulation of Supramolecular Hydrogels by Metal Complexation

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.

Enhanced Shape Memory Metal-Coordinated Poly(aryl ether ketone)s with Tunable Gradient-Deformation Behaviors as well as Self-Healing and Reprocessing Abilities

“…and noncovalent bonds (hydrogen bonds, coordination bonds, host–guest interactions, etc. ), which have been widely integrated into the SMP matrix for the fabrication of multifunctional thermally adaptive SMPs. , …”

“…), which have been widely integrated into the SMP matrix for the fabrication of multifunctional thermally adaptive SMPs. 49,50 Poly(aryl ether ketone) (PAEK) exhibits the excellent mechanical performances and thermal stability; therefore, using the engineering thermoplastic PAEK as the SMP matrix polymer is expected to satisfy the requirements of mechanical properties and could extend the utilization potential of SMPs in engineering structures. 51−55 At present, there are several papers investigating the modified shape memory PAEK materials, which mainly focus on the thermoplastic structures and properties.…”

Supramolecular Assembly and Thermogelation Strategies Using Peptide–Polymer Conjugates

“…89,90 They recently developed a C 3 -symmetric dendritic conjugate consisting of the triphenylalanine FFF sequence and dendritic OEG. 91 For the conjugate synthesis, the N 3 -GFFF−OH peptide was first synthesized by SPPS. The peptide was then coupled to an amine-containing OEG dendron by an amidation reaction.…”

“…Thermoresponsive conjugates have also been developed using oligo­(ethylene glycol) (OEG) chains conjugated to peptide motifs . This approach was notably investigated in the Besenius group. , They recently developed a C 3 -symmetric dendritic conjugate consisting of the triphenylalanine FFF sequence and dendritic OEG . For the conjugate synthesis, the N 3 -GFFF–OH peptide was first synthesized by SPPS.…”