Chemical modification of polyaniline powders by surface graft copolymerization

Abstract

Chemical modification of emeraldine (EM) based powders via thermally induced surface graft copolymerization with acrylic acid (AAc), 4- styrenesulfonic acid (SSAc) and amphoteric N,N'- dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS) was carried out in aqueous media. The effects of temperature on graft copolymerization and Mohr's salt on homopolymerization were also studied. The chemical composition and structure of the graft-copolymerized powders were studied by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. In all cases, the graft yield increased with the monomer concentration and the temperature used for graft copolymerization. Certain Mohr's salts effectively inhibited the production of the homopolymers. Graft copolymerization with AAc and SSAc readily gave rise to self-protonated and semi-conductive EM powders, with the conductivity increasing with the extent of grafting. However, steric hindrance and spatial configuration of the grafted chains had substantially limited the extent of protonation of the EM substrate by the protonic acid functional groups of these chains.