Preparation of polyimide/multi‐walled carbon nanotubes composite aerogels with anisotropic properties

In this study, a series of polyimide/multi‐walled carbon nanotubes (PI/MWCNTs) composite aerogels with anisotropic properties were fabricated. First, the poly(amic acid) ammonium salt (PAS)/MWCNTs suspension was prepared by blending poly(amic acid), deionized water, triethylamine, MWCNTs, and CNT dispersant with the aid of ultrasonication treatment. Afterwards, the aqueous PAS/MWCNTs suspension was unidirectionally frozen at −65 ± 5°C, then followed by freeze‐drying. Subsequently, the PI/MWCNTs composite aerogels were obtained after thermal imidization treatment. Morphology observations revealed that PI/MWCNTs composite aerogels exhibited a “hive‐like” structure while viewed along the freezing direction, whereas a typical channel‐like pore structure was observed perpendicular to the freezing direction. This typical structure rendered PI/MWCNTs composite aerogels with anisotropic properties such as heat conduction, electrical conductivity as well as electromagnetic interference shielding effectiveness when the aerogels were characterized at different directions.