Electrically and thermally healable nanocomposites via one-step Diels-Alder reaction on carbon nanotubes

Carbon nanotubes (CNTs) were directly employed as reactive fillers in furan-pendant polyketones via the Diels-Alder (DA) reaction. CNTs and furan groups function as dienophile and diene, respectively, forming a reversible crosslinking network. Here, pristine CNTs not only serve as crosslinking agents, but also improve the thermal and electrical conductivity. The DA covalent linkage was confirmed by IR, TGA, DSC, elemental analysis and dispersion tests. This one-step approach offers a facile route to synthesize reversibly crosslinked thermoset polymer nanocomposites. The rigidity of the nanocomposites could be controlled through the number of furan groups in order to achieve distinct properties. The nanocomposites demonstrated dynamic temperature-dependent behavior due to the retro Diels-Alder reaction. Cyclic tests via rheology showed good reversibility below 120 °C. However, an irreversible increase of modulus was observed at higher temperatures, which is possibly attributed to a side reaction. At filler loadings above 5%, both electrical and thermal self-healing tests showed good results. The Diels-Alder reaction between CNTs and furan-pendant polymers opens up a new possibility of directly employing fillers in the polymer matrix without any prior modifications. It is also possible to use other fillers with diene/dienophile properties in future reversible polymer nanocomposites.