Ultrafast Self-Healable Interfaces in Polyurethane Nanocomposites Designed Using Diels-Alder "Click" as an Efficient Microwave Absorber

In the recent times, multifunctional materials have attracted immense interest. Self-healing polymers are in great demand in almost every coating application. With an increase in electromagnetic (EM) pollution, curbing the same has become an urgent necessity. Lightweight coatings and conducting polymeric materials are being highly researched upon in this regard, and combining these properties with self-healing systems would open new avenues in EM interference (EMI) shielding (specifically in the microwave frequency domain) applications. In the current study, a novel approach toward the development of microwave shielding materials capable of self-healing through microwave heating has been attempted. A covalently cross-linked material was developed using Diels-Alder (DA) chemistry, which shows self-healing properties when stimulated by heating. Herein, reduced graphene oxide grafted with magnetite nanoparticles (rGO/Fe3O4) was covalently crosslinked to thermoplastic polyurethane using DA chemistry. The addition of multiwalled carbon nanotubes into these nanocomposites led to exceptional EM wave shielding and self-healing properties through a synergistic effect. The synergism led to exceptional EMI shielding of -36 dB, primarily through absorption in the microwave region of the EM spectrum. When used in the form of thin coatings of about 1 mm in thickness, the shielding value reached -28 dB, manifesting in more than 99% attenuation of EM waves through absorption. The material was also found to be capable of healing scratches or cuts through microwave irradiation.