Molecular metal oxide cluster-soldered interpenetrating polymer network “hosts” carbon nanotube “guest” for green millimeter wave absorption

Abstract

Host–guest chemistry, although historically developed in organic and aqueous solutions, recently has gained interest in designing systems assembled on solid surfaces. Following this unique chemistry, structural complexes consisting of copper-based molecular metal oxide clusters soldered onto a sequential interpenetrating polymer network (IPN) were designed to host carbon nanotubes constructed via electrostatic assembly designed to absorb millimeter waves. Such unique structures offer myriad solutions in this era of 5G and IoT (internet of things) wherein lightweight, ultrathin, and multifunctional properties have become a prerequisite to protect precise electronics from stray signals. This strategy offers to trigger and tune the surface charge of the host (Keggin type Cu-POM-soldered IPN), which allows the guest (positively charged CNTs) to self-assemble. The resulting construct (thickness ∼56 μm) demonstrated synergistic enhancement in millimeter wave absorption (>90% absorption in X-band, 8.2–12.4 GHz) through this unique host–guest assembly with a remarkable green index (g_s ≈ 1.7). This study opens new avenues in designing lightweight constructs for millimeter wave absorption that are not possible via conventional routes of dispersing nanoflakes in composites.