Bio-Derived Ionic Coacervate-Engineered Cellulose Liquid Crystal Films for Electrically Reconfigurable Microwave Absorption

Abstract

The increasing demand for sustainable and intelligent electronics calls for microwave absorption (MA) materials that are simultaneously renewable, mechanically compliant, and electrically reconfigurable-capabilities rarely achieved in current systems dominated by rigid and static absorbers. Here, we introduced a new design strategy that leveraged an ionic coacervate-engineered cellulose liquid crystal film (CLCF) to realize fully reversible, low-voltage, and structurally governed modulation of MA performance. The CLCF integrated a cholesteric cellulose nanocrystals (CNC) scaffold with a poly(ionic liquid) (PIL)/ionic liquid (IL) coacervate network, in which mobile ions, electrostatic interactions, and chiral helical ordering operated cooperatively. This hierarchical architecture preserved long-range cholesteric ordering while introducing ion-transport pathways and heterogeneous interfaces, enabling pronounced field-induced helical reorganization and synergistic conductive, dipolar, and interfacial polarization losses. As a result, the film exhibited voltage-dependent tuning in minimum reflection loss (RLmin), peakfrequency position, and effective absorption bandwidth (EAB). At 0 V, the CLCF displayed an RLmin of -41.74 dB at 11.5 GHz and an EAB of 2.96 GHz; increasing the voltage to 16 V triggered a lowfrequency absorption peak and enhanced performance to an RLmin of -49.02 dB at 8.4 GHz with an EAB of 4.0 GHz, fully covering the Xband. Meanwhile, the incorporation of PIL effectively mitigated the inherent brittleness of CNC assemblies, yielding a flexible, biodegradable, and processable film platform. This work establishes a sustainable and mechanistically distinct route for constructing electrically reconfigurable electromagnetic materials, offering a transferable strategy for next-generation adaptive and eco-friendly electronic systems.