Self-assembly is one of nature’s primary pathways for creating tough, responsive materials through the precise tuning of non-covalent interactions. In one example, polychaete marine worms exhibit Zinc-Histidine (Zn-His) coordination crosslinks in their jaw which serve to mechanically reinforce the material. Furthermore, the depletion of Zn2+ down the length of the mandible leads to a local decrease in crosslink density, affording the polychaete jaw a transition from stiff to soft mechanics that offers enhanced toughness through energy absorption and dissipation near the jaw’s tip and base, respectively. In an effort to mimic this localization of non-covalent interactions, we apply a supramolecular interpenetrating network (SIPN) framework wherein one of the phases consists of a Zn-coordinating telechelic supramolecular polymer confined by a covalently crosslinked poly(ethylene glycol) (PEG) network. These SIPNs display tunable mechanics driven by the energy dissipation capabilities of the supramolecular polymer during deformation. This shift in mechanics is supported by a change in the materials’ energy dissipation pathway. When the supramolecular polymer is present as well-dispersed droplets in the PEG matrix, the opening of cavitational voids provide toughness enhancement, whereas upon phase inversion this toughness enhancement is lost due to the disruption of local non-covalent interactions by the crosslinked PEG as visualized by small-angle X-ray scattering (SAXS). To drive metal-ligand coordination gradients, the SIPN films are exposed to a competitive ligand that travels up the length of the film via capillary action. The migration of the Zn2+ ions disrupts supramolecular order, resulting in a decrease in domain size as measured by SAXS. Using this SIPN platform, we explore how changes in network architecture impact the stimuli-responsive nature of the confined supramolecular interactions.

Bio-inspired supramolecular interpenetrating networks: Impacts of supramolecular confinement on mechanics and stimuli-responsive behavior

2019 Fall National Meeting

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