SYNTHESIS AND CHARACTERIZATION OF POLYANILINE DERIVATIVES - POLY(2-ALKOXYANILINES) AND POLY(2,5-DIALKOXYANILINES)

A series of 2-alkoxyanilines and 2,5-dialkoxyanilines with alkyl chain s containing n = 1, 2, 4, and 6 carbon atoms have been electropolymeri zed in acidic conditions and characterized by several techniques. The corresponding neutral polymers were found to be soluble in chloroform and tetrahydrofuran. On the other hand, chronoamperometry experiments have shown that the presence of long alkoxy groups (n = 4 and 6) decre ases the rate of polymerization, giving materials with a lower degree of polymerization. Electrochemical and spectroscopic measurements have demonstrated that the electron-donating effects of the side chains ar e more significant for 2,5-dialkoxyanilines and for the corresponding polymers. Moreover, the presence of electron-donating substituents has allowed a better characterization of the charge carriers in fully oxi dized polyanilines. Indeed, in agreement with electrochemical results, in situ ESR experiments displayed two signals with similar g values, related to the presence of radical cations formed during the leucoemer aldine-emeraldine transition and the emeraldine-pernigraniline transit ion. However, these radical cations were found to be more localized, w ith respect to polyaniline. Fully oxidized poly(2,5-dialkoxyanilines) were found to be partially protonated at pH between -0.5 and 3, by ele ctrochemical quartz crystal microbalance (EQCM) analysis. On the other hand, in situ conductivity measurements suggested that protonated imi nes do not act as efficient charge carriers. Finally, conductivity of 0.1 S/cm were found for disubstituted materials with short alkoxy grou ps (n 1 and 2), whereas a decrease of 3-5 orders of magnitude were obs erved for materials bearing longer alkoxy groups (n = 4 and 6).