Construction of temperature-responsive helical carbon nanofibers-based composites toward switchable microwave absorption

Intelligent and adjustable microwave absorption (MA) materials capable of responding to environmental changes are still in great demand for modern electromagnetic interference protection. In this work, a temperature-responsive composite, denoted as HGPC, was prepared via in situ graft polymerization of poly(N-isopropylacrylamide) (PNIPAAm) onto helical carbon nanofibers (HCNFs). HGPC retains its structural integrity and percolation network below the lower critical solution temperature. As the temperature increases, the contraction of PNIPAAm chains disrupts the morphology and structure of HCNFs, correspondingly weakening both the dielectric and magnetic losses of HGPC. At 20 degrees C, HGPC exhibits a minimum reflection loss (RLmin) of -54.5 dB and an effective absorption bandwidth (EAB) of 4.2 GHz. In contrast, at 50 degrees C, HGPC fails to achieve an effective RLmin (<-10 dB). The temperature-responsive behavior arises from the thermal transition of PNIPAAm. This study provides a new foundation for the development of smart microwave-absorbing materials.