Anisotropic MXene/waterborne polyurethane/polypyrrole ternary composite aerogels for enhanced electromagnetic interference shielding and multifunctional applications

As the proliferation of electromagnetic interference (EMI) radiation pollution becomes increasingly severe, developing lightweight, flexible, and low-reflective multifunctional EMI shielding aerogels is crucial for portable wearable electronic devices. In this work, we first utilize directional freezing technology to prepare MXene/ waterborne polyurethane (WPU) aerogel and then construct a continuous polypyrrole (PPy) conductive network through in-situ chemical oxidative polymerization, resulting in a MXene/WPU/PPy composite aerogel with anisotropic pore structure. By adjusting the monomer concentration and the polymerization time of PPy, the synthesized composite aerogel exhibits excellent compressive resilience and strength (100.1 kPa). In the X-band (8.2-12.4 GHz), the composite aerogel with a thickness of only 5 mm exhibits an average EMI shielding effectiveness (EMI SE) in the axial direction of 47.3 dB, while the EMI SE can reach 72.9 dB in the radial direction, with an absolute shielding effectiveness (SSE/t) as high as 2509.7 dB cm2 g-1. This phenomenon indicates that the material exhibits anisotropic electromagnetic shielding properties with a predominant absorption-based shielding mechanism. Additionally, the MXene/WPU/PPy composite aerogel demonstrates satisfactory piezoresistive sensing properties and Joule heating de-icing capabilities, making this multifunctional composite aerogel promising for applications in green shielding, health monitoring, human-computer interaction, and thermal management of wearable electronic devices.