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 chains containing n = 1, 2, 4, and 6 carbon atoms have been electropolymerized 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) decreases 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 are 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 oxidized 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 leucoemeraldine-emeraldine transition and the emeraldine-pernigraniline transition. However, these radical cations were found to be more localized, with respect to polyaniline. Fully oxidized poly(2,5-dialkoxyanilines) were found to be partially protonated at pH between -0.5 and 3, by electrochemical quartz crystal microbalance (EQCM) analysis. On the other hand, in situ conductivity measurements suggested that protonated imines do not act as efficient charge carriers. Finally, conductivity of 0.1 S/cm were found for disubstituted materials with short alkoxy groups (n 1 and 2), whereas a decrease of 3-5 orders of magnitude were observed for materials bearing longer alkoxy groups (n = 4 and 6).