Jake Song

Jake Song

NIH F32 Postdoctoral Fellow at Stanford University

Bio-inspired soft materials

Metal-coordinate bonds are a key binding motif found in many biogenic materials that exhibit extraordinary mechanical properties, such as the hard jaws of the Glycera and Nereis, the tough byssal threads of the Mytilus, and the adhesive mucus of the Arion. These bonds are strong (near-covalent), reversible, and tunable, thus offering a wide palette for the bioinspired design of structural materials with advanced functionalities. Working in the Holten-Andersen group and the McKinley group at MIT, I leveraged metal-coordinate bonds to develop polymeric materials with tunable viscoelasticity, structure, and stimuli-responsivity.

Kinetics of metal-coordinate bonds

A rational understanding of the energetic landscape of the metal-coordinate bonds is essential for designing metal-coordinate materials with tunable mechanics. Using common histidine-metal coordinate bonds as a model motif, we showed that the width and ruggedness of the energy landscape of the coordination bonds play a critical role in their kinetics, and thus the resulting mechanical properties of materials with histidine-metal coordinate bonds. [1]. We also showed that these energy landscapes can be tuned by changing the coordination state via metal-ligand stoichiometry in histidine-containing materials [2].


Summary of the coordination-state-dependent binding hierarchy between transition metals and imidazole-based ligands, taken from Song et al [1].

Metal-coordinate particle gels

Leveraging the strong yet reversible coordination bonds between catechol and metal oxide surfaces, we designed a hydrogel platform in which solvent-stabilized metal oxide nanoparticles are cross-linked by catechol-functionalized polymers. In contrast to conventional particle gels which are constructed via arrested phase separation, these gels are constructed via tunable limited-valency interactions between solvent-stable metal oxide particles and polymer linkers. This paved way for the design of a unique “equilibrium” particle gel system which are phase-stable with tunable morphologies and percolation thresholds [3]. These gels also exhibit classical signatures of arrested dynamics, and was used in another study of mine where I studied the microscopic origins of such relaxation dynamics, on which you can find more details [here]. We also showed that a combination of metal oxide particles and metal ions give rise to dual-junction-functionality gels which can be both load-bearing and self-healing [4].


Systematic control of iron oxide particle self-assembly and percolation behavior with limited-valency metal-coordinate polymer linkers in metal-coordinate composite hydrogels, taken from Song et al [3].

Metal-coordinate mineralized gels

Drawing inspiration from the fabrication process underlying strong and tough biogenic composite materials such as the abalone shell and chiton tooth – in which inorganic components are /mineralized/ in an organic scaffold – we designed metal-coordinate particle gels in which metal oxides were mineralized from a metal-ion-coordinated polymer hydrogel scaffold, rather than synthesized and added externally. We showed that a rapid mineralization process can yield particle gels with increased stiffness and magnetization at extremely low volume fractions [5]. We further showed that a longer nucleation and growth process can lead to hydrogels with a high concentration of metal oxides, thus resulting in hydrogels which are soft, viscoelastic, yet highly magnetic [6].


Design blueprint for soft and viscoelastic hydrogels via mineralization in metal-coordinate gels, taken from Song et al [6].

References

  1. Song, J.*, Khare, E*., Rao, L., Holten-Andersen, N. “Coordination Stoichiometry Effects on the Binding Hierarchy of Histamine and Imidazole-M2+ Complexes”. Macromolecular Rapid Communications. 44(17), 2300077 (2023)
  2. Khare, E., Cazzell., S., Song, J., Holten-Andersen, N., & Buehler, M. “Molecular Understanding of Ni2+-Nitrogen Family Metal-Coordinated Hydrogel Relaxation Times Using Free Energy Landscapes.” Proceedings of the National Academy of Sciences. 120(4), e2213160120 (2023)
  3. Song, J., Rizvi, M. H., Lynch, B. B., Ilavsky, J., Mankus, D., Tracy, J, B., McKinley, G. H., & Holten-Andersen, N. “Programmable Anisotropy and Percolation in Supramolecular Patchy Particle Gels.” ACS Nano. 14(12). 17018-17027 (2020)
  4. Song, J.*, Li, Q.*, Chen, P., Keshavarz, B., Chapman, B., Tracy, J. B., McKinley, G. H., & Holten-Andersen, N. “Dynamics of Dual Metal-Coordinate Networks with Ion and Nanoparticle Cross-Link Junctions.” Journal of Rheology. 66(6). 1333-1345 (2022)
  5. Kim, S., Registsky, A. U., Song, J.., Ilavsky, J., McKinley, G. H., & Holten-Andersen, N. “In-Situ Mechanical Reinforcement of Polymer Hydrogels via Metal-Coordination Crosslink Mineralization.” Nature Communications. 12(1), 1-10 (2021)
  6. Song, J.., Kim, S., Saouaf, O., Owens, C., McKinley, G. H., & Holten-Andersen, N. “Soft Viscoelastic Magnetic Hydrogels from the In Situ Mineralization of Iron Oxide in Metal-Coordinate Polymer Networks”. ACS Applied Materials and Interfaces. 15(45), 52874-52882 (2023)