Abstract: By comparing the redox potentials of poly-2, 5-dimethoxyaniline(PDMAn), poly-o-toluidine(POT ) and poly m chloroaniline(PmClAn) membrane modified electrodes, the morphology and crystal face orientation of Pt deposited on these polymers and isopropanol oxidation behavior on the platinized polyaniline electrodes, the relation of electrochemical properties of polyanilines to ring substituted groups in the polymers and the influence of different polyaniline on Pt deposition and the catalytic properties of platinized polyaniline modified electrodes were discussed in terms of the electronic and steric effects. The results indicated that among 3polyanilines, the redx potential of PDMAn was the most negative, and that of POT was less negative, and that of PmClAn was the most positive. The electrodeposition mechanisms of Pt particles on POT and on PDMAn membranes were different from that on PmClAn membrane. The Pt particles deposited on polyanilines were inclined towards the preferred orientation of Pt(200) crystal face, but the degree of preferred orientation depended on polymers. The preferred orientation on POT was stronger than that on PDMAn, and the weakest on PmClAn. The potentials of isopropanol oxidation on platinized polyaniline modified electrodes rely on the nature of polyanilines matrix. On POT modified electrode the isopropanol oxidation mainly occurs in the potential region where POT is electroactive, but on PDMAn and PmClAn modified electrodes it takes place in the potential region same as that on Pt. It follows that polymer matrix was not only as disperse media of Pt particles, but also exerts catalytic actions.

Key words: Ring-substituted polyanilines, Metal-polymer composite, Isopropanol electrooxidation, Chemically modified electrodes