Fig. 2: Construction of CNT/PEI double network.

a Schematic of the vacuum impregnation strategy which can promote the in-depth infiltration of PEI. b The raw CNT film with rich sub-µm pores. c, d Surface and interior morphologies of a PEI-infiltrated CNT film. e The interior morphology of a PEI solution-soaked CNT film. f TGA curves of the raw CNT film, CNT/PEI film, and the 40% stretched I-treated CNT/PEI film collected under nitrogen atmosphere. g FTIR curves of the raw CNT film, CNT/PEI film, and the 40% stretched I-treated CNT/PEI film, in which the characteristic peaks of different bond were marked.