Shape memory HCNTs/PANI/WPU aerogels as dynamically tunable microwave absorbers in response to mechanical deformation

Intelligent microwave absorption (MA) materials capable of dynamic regulation are becoming an urgent challenge owing to increasingly complex application conditions. The desirable shape memory polymer enables porous structure with self-fixable and recoverable mechanical deformation. Herein, helix carbon nanotubes/polyaniline/polyurethane aerogels (HCNTs/PANI/WPU, HPWA) were developed through directional freezing. Both component modulation and shape transformation are simultaneously constructed to achieve dynamically adjustable MA property under mechanical deformation responses. Specially, smart HPWA-2 possesses the minimum reflection loss ( RL min ) of –65.58 dB and effective absorption bandwidth (EAB) of 3.13 GHz at a simulated thickness of 3.95 mm. More importantly, HPWA-2 achieves dynamically tunable MA property with RL min of –39.9 dB and EAB of 2.84 GHz in original shape, while it obtains unexpected RL min of –66.6 dB and EAB exceeding 4.2 GHz as varying compression strain to 20 %. The real-time regulation of RL min and EAB along with frequency is attributed to adjustable complex permittivity driven by compressing and releasing of pore channels based on micro-capacitor theory. The hydrogen bonding between PANI and WPU strengthens the porous walls to ensure stable shape deformation and recovery. Besides, the radar cross section reduction reaches –39.74 dB∙m 2 when the incidence theta is 0°. This integration of MA property and shape memory effect would provide another insight for designing intelligent absorbers.