Smart shape memory composite foam enabled rapid and conformal manipulation of electromagnetic wave absorption performance

With the development of communication and electronic technologies, smart electromagnetic wave (EMW) absorption materials with tunable performance are highly desirable for applications under complicated electromagnetic circumstances. However, the performance of the ordinary EMW absorption materials is dominated by their electromagnetic parameters which are constant unless their compositions are changed. This study presents a porous EMW absorption material with adjustable effective absorption bandwidth (EAB) and reflection loss (RL) to satisfy the requirements of tunability for complex electromagnetic applications. First, a composite foam is fabricated by assembling the reduced graphene oxide (rGO) to the melamine sponge (MS) framework. Next, the thermoplastic polyurethane (TPU) is introduced to endow the MS/rGO composites with the desired shape memory property after crosslinking. In specific, the obtained MS/rGO composites show high flexibility, elasticity, and low density of 10.7 mg cm-3, and present the minimum RL of -63.29 dB with EAB of 7.18 GHz. Additionally, the tunable EMW absorption performance of MS/rGO-TPU composites is achieved through their shape memory effect. Notably, the EAB can be adjusted to a wide range from 5.5 to 18 GHz under the compressive deformations of those composites as modulated by cooling/heating, and correspondingly the minimum RL changes from -15.4 dB down to -39.2 dB. In a word, the smart, lightweight MS/rGO and MS/rGO-TPU composite foams with adjustable EMW absorption performance are strong candidates for practical applications in complex electromagnetic fields.