G. Daprano et al., SYNTHESIS AND CHARACTERIZATION OF POLYANILINE DERIVATIVES - POLY(2-ALKOXYANILINES) AND POLY(2,5-DIALKOXYANILINES), Chemistry of materials, 7(1), 1995, pp. 33-42
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).