Self-healing materials have potential applications ranging from coatings, sealants, adhesives, etc. Polymer networks containing reversible or dynamic cross-linkers are well suited to the creation of self-healing materials. This is because even if the material is damaged or cut, the exchangeable cross-links allows the material to mend itself and recover from the damage. However, the exchangeable bonds that provide the self-healing ability, also make the material highly susceptible to creep deformation over time. This introduces a tradeoff between desirable dynamic character and unwanted susceptibility to creep. To circumvent this intrinsic tradeoff, a new generation of self-healing materials, containing two orthogonal and distinct dynamic cross-linkers, were synthesized in this project to provide high material strength and resistance to creep, without compromising the rate of healing. Incorporating cross-linkers where one linker exchanges rapidly, and the other exchanges slowly or only upon external stimulus can attain this balance of objectives. One dynamic linker uses relatively weak non-covalent bonds such as hydrogen bonds to give a rapid rate of exchange and healing. The second cross-linker utilizes significantly stronger and stimulus responsive dynamic covalent linkages, such as the bonds in a Diels-Alder adduct, or thiol Michael adducts. Mechanical testing is used to evaluate the performance of these new self-healing materials. Specifically, the strain at break under tension is used as a measure of material’s mechanical strength, and performed on undamaged and healed materials, to quantify healing. The recovery of these materials was generally very good, and significantly better than control samples. In addition, creep and stress relaxation tests were performed to determine the material’s stability under load.

Self-healing, malleable and creep limiting materials using both supramolecular and reversible covalent linkages

254th National Meeting (2017)

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