STERIC AND ELECTRONIC EFFECTS IN METHYL AND METHOXY SUBSTITUTED POLYANILINES

Various methyl and methoxy monosubstituted and disubstituted anilines were electropolymerized in acidic conditions. From UV-visible absorption and electrochemical measurements, it has been found that methyl substituted anilines give polymers which are less planar than the methoxy derivatives. This has been explained in terms of more pronounced steric effects of the methyl group than those induced by the methoxy group. However, alkoxy monosubstituted anilines exhibit lower conductivities than those obtained with the alkyl derivatives. This has been explained by a less regular structure for poly(alkoxyanilines). Indeed, as shown by the cyclic voltammetry experiments, the selectivity of the head-to-tail couplings is reduced by the incorporation of a methoxy group at the ortho position. However, more regular materials have been obtained with 2,5-disubstituted polyanilines. For instance, poly(2,5-dimethoxyaniline) exhibits a high conjugation length and a good conductivity (ca. 0.3 S cm-1).