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Bio-Inspired Gels Show Promise as Self-healing Materials with Properties Controlled by Metal Ions

Nature has evolved numerous mechanisms for the self-healing of damaged tissues and structures.  MIT MRSEC researchers have shown first successes in establishing a new class of smart polymer materials with controllable network junctions by combining Diels-Alder reactions with bio-inspired metal coordinate crosslinking to generate multi-functional polymers capable of self-assembly into and onto nano-structures with tunable properties (see Figure). Specifically, by decorating polymer backbones with ligands known to self-assemble into well-defined metal-coordinated geometric shapes or with ligands known to bind onto metal nanoparticles with tunable adhesive energy, this collaborative research has led to the assembly of materials with kinetically controllable crosslink junctions. With polymer material assembly now directly controlled via network junction kinetics and material mechanics dependent on measurable network junction structural dynamics, this effort has established an ideal platform upon which to explore the function of simple engineered bio-inspired motifs in complex hydrogel properties such as self-healing, controllable energy dissipation and remote-controlled transport. 


Figure: Diagram illustrating a bio-inspired hybrid polymer material design approach. By assembling polymer networks via Diels-Alder covalent crosslink chemistry and coordinate binding onto metals, self-assembly into multi-functional nanoscopic crosslink structures provides unprecedented control over polymer crosslink dynamics orthogonal to network structural mechanics.