Anisotropic electromagnetic wave shielding performance in Janus cellulose nanofiber composite films

Abstract

Herein, Janus multi-walled carbon nanotubes/cellulose nanofibers/poly (3, 4-ethylenedioxythiophene):polystyrene sulfonate (CNT/CNF/PEDOT:PSS) composite films were prepared via a layer-by-layer vacuum filtration to achieve anisotropic electromagnetic wave shielding materials. Conductive CNT/CNF and PEDOT:PSS are located on both sides of the composite film to create Janus structure, while insulated CNF acts as an intermediate layer to separate the two conductive layers. The Janus conductive structure of the composite film gives anisotropic electromagnetic interference shielding effectiveness (EMI SE). The EMI SE values of electromagnetic waves incident from the CNT/CNF layer and PEDOT:PSS layer are much different. The average differentiation of SE at two sides (ΔSE‾) values are much dependent on surface conductive differentiation and thickness of middle layer. The maximum ΔSE‾ can reach 20.5 dB for the samples with 60 % CNT in CNT/CNF layer, 2 ml PEDOT:PSS solution in PEDOT:PSS layer and 50 mg CNF in middle layer. In addition, the electromagnetic simulation is also carried to discuss the anisotropic shielding mechanism of the samples. The simulation results are consistent with the experimental results to further explore the EMI mechanism of the Janus composite films.