5-Sulfoisophthalic acid monolithium salt doped polypyrrole/multiwalled carbon nanotubes composites for EMI shielding application in X-band (8.2-12.4 GHz)

This article describes the synthesis and characterization of highly conductive polypyrrole (PPy)/multiwalled carbon nanotube (MWCNT) composites prepared by in situ polymerization of pyrrole using 5-sulfoisophthalic acid monolithium salt [lithio sulfoisophthalic acid (LiSiPA)] as dopant and ferric chloride as oxidant. Several samples were prepared by varying the amounts of MWCNTs ranging from 1 to 5 wt %. Scanning electron microscope and transmission electron microscope images clearly show a thick coating of PPy on surface of MWCNTs. The electrical conductivity of PPy increased with increasing amount of MWCNTs and maximum conductivity observed was 52 S/cm at a loading of 5 wt % of MWCNTs. Pure PPy prepared under similar conditions had a conductivity of 25 S/cm. Electromagnetic interference (EMI) shielding effectiveness (SE) also showed a similar trend and average EMI shielding of -108 dB (3 mm) was observed for sample having 5 wt % MWCNT in the frequency range of 8.2-12.4 GHz (X-band). The light weight and absorption dominated total SE of -93 to -108 dB of these composites indicate the usefulness of these materials for microwave shielding. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45370.