Synthesis of needle-like polyanilines

Abstract

Needle-like polyanilines were prepared in aqueous media by chemical oxidation. p-Toluenesulfonic acid (pTSA) was used to protonate aniline (ANi) and readily made the anilinium complex. By slowly adding ammonium peroxydisulfate (APS) at 15 degrees C, polyanilines were prepared in the micelles and grew to be needle-like aggregates potentially useful as conductive fillers for electromagnetic interference shielding and radarabsorbing materials. The needle-like aggregates of protonated polyaniline prepared at 15 degrees C and 0.5 M aniline concentration with 3 h of APS addition time showed conductivity up to 3 S/crn and a maximum aspect ratio of 26 L/D. They were observed by scanning electron microscopy to peel off partially into fibrils after washing. The needle-like polyaniline-pTSA complexes prepared with 0.5 M aniline concentration showed good thermal stability up to 200 degrees C. The high conductivity of the needle-like aggregates was ascribed to their well-developed crystalline structures, compared with those of spherical particles.