Mechanically Robust, Self-Healing Polymer Nanocomposites with Tailorable Nanoparticle-Based Bonds

A trade-off between self-healing kinetics and mechanical robustness has been one of the major challenges of intrinsically self-healing polymers. Here, carboxylic acid-functionalized nanoparticles are introduced as nanoparticle-based bonds to cross-link poly(N,N-dimethylacrylamide) and assemble a mechanically robust polymer nanocomposite through complementary hydrogen bonds at the interface. These nanocomposites exhibit self-healing behavior, a glass transition temperature above 120 degrees C, a fast stress-relaxation rate, and a modulus in the GPa range. The materials properties can be further tuned by the nanoparticle concentration, size, moisture content, and surface ligand density. Lastly, these materials undergo reversible disassembly where nanoparticle-based bonds are separated from polymers using a low-energy density separation method and reassembly where the material exhibits an identical T-g and storage modulus relative to the initial material. This work not only demonstrates how tailored nanoparticles can be used to precisely engineer materials properties but also introduces the concept of removable nanoparticle-based bonds that can be recycled to generate polymer nanocomposites.