Enhancing electromagnetic interference shielding of shape memory polyimide film via co-assembly of nano-cellulose and carbon nanotubes.

Shape memory polyimide (SMPI) is a promising candidate for electromagnetic interference shielding (EMI SE) due to excellent flexibility and resistance in harsh condition. However, the significant aggregation of conductive fillers severely compromises its performance. Herein, a co-assembly strategy was developed through promoting the dispersion of carboxylated multi-walled carbon nanotubes (cMWCNTs) by using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized cellulose nanofibrils (TOCNs). Thanks to the high aspect ratio and abundant surface-exposed negatively charged carboxyl groups, TOCNs promotes electrostatic repulsion and physical entanglement with cMWCNTs, thereby effectively preventing conductive fillers aggregation and facilitating the formation of a continuous conductive network within the SMPI matrix. As a result, the electrical conductivity of the composite film increases from 17.8 ± 3.7 to 187.7 ± 7.4 S/m, while the total electromagnetic interference shielding (EMI SET) increases from 13.8 ± 0.7 dB to 26.4 ± 0.8 dB. In addition, the shape memory property is well preserved. This work presents a feasible road for constructing multifunctional SMPI-based composites that integrating superior electromagnetic shielding performance with reliable actuation capabilities.