The behavior of Fe3+ coordination in alginate-catechol networks

[摘要] Mussel byssal threads allow mussels to remain steadfast on ocean rocks despite ocean turbulence, facilitated by the simultaneous elasticity and hardness of the byssus coating. Inspired by the metal-coordination chemistry found in byssus coating, scientists have synthesized an array of self-healing hydrogels with catechol-modified, 4-branched PEG (4cPEG) and various metal ions, primarily Fe3+. While considerable testing has been conducted with 4cPEG, the effects of changing the polymer backbone have not been investigated extensively. Here, alginate was chemically modified with catechol attachments (Alg-C), and metal-coordinated with Fe3+ to yield a self-healing network with similar qualities to 4cPEG gels. Rheological measurements indicated that metal-coordination played a dominant role in the bulk mechanics of the network, although the ionic crosslinking caused the gel to act as a solid across all frequencies, in contrast to 4cPEG. In addition, the stiff alginate backbone caused the metal-coordinate bond in itself to act on a longer time scale. Color changes in the Alg-C gel indicated that excess catechol on the backbone was oxidizing. While rheology confirmed the metal-coordination in the Alg-C network, UV-vis absorption measurements provided less certain data. Nonetheless, this study shows that metal-coordination is highly dependent on the polymer backbone, but may still be used in a variety of polymer networks.

[发布机构] Massachusetts Institute of Technology