Chemical modification of polyaniline powders by surface graft copolymerization

Chemical modification of emeraldine (EM) based powders via thermally induce d surface graft copolymerization with acrylic acid (AAc), 4-styrenesulfonic acid (SSAc) and amphoteric N,N'-dimethyl(methacryloylethyl)ammonium propan esulfonate (DMAPS) was carried out in aqueous media. The effects of tempera ture on graft copolymerization and Mohr's salt on homopolymerization were a lso studied. The chemical composition and structure of the graft-copolymeri zed powders were studied by X-ray photoelectron spectroscopy (XPS) and Four ier transform infrared (FTIR) spectroscopy. In all cases, the graft yield i ncreased 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 conductiv ity increasing with the extent of grafting. However, steric hindrance and s patial configuration of the grafted chains had substantially limited the ex tent of protonation of the EM substrate by the protonic acid functional gro ups of these chains. (C) 2000 Elsevier Science Ltd. All rights reserved.