A Tough Temperature-Responsive Composite for Switchable Microwave Absorption

Smart microwave absorption (MA) materials that respond to environmental stimuli are highly sought after for advanced electromagnetic interference protection, particularly those with superior mechanical properties. In this study, we present a temperature-responsive composite material composed of poly(<i>N</i>-isopropylacrylamide) (PNIPAAm) and a polyurethane (PU) sponge loaded with graphene oxide (PU@GO), referred to as PGPC. This composite exhibits switchable MA behavior below and above its lower critical solution temperature (LCST). Below LCST at 20 °C, the material shows minimal MA effectiveness (reflection loss < -10 dB), while at 50 °C, the reflection loss significantly improves to -42 dB with a bandwidth of 3.45 GHz. Structural characterization, both in situ and ex situ, reveals that this tunable behavior is driven by the reversible dissociation and reconstruction of a three-dimensional (3D) graphene network, triggered by the thermally induced movement of PNIPAAm molecular chains grafted onto the graphene sheets. Furthermore, the incorporation of PU enhances the composite's mechanical properties. The ability of PGPC to combine switchable MA performance with mechanical robustness makes it a promising candidate for intelligent, adaptive electromagnetic interference protection material, addressing current technological needs in dynamic environments.