Aniline is polymerized by chemical oxidation with FeCl3 in water. At a
n optimum reaction condition, the resulting polyaniline has a number a
verage molecular weight of 20 400 and a yield of 51%. Chemical and ele
ctrochemical analyses show that the polyaniline is emeraldine. FeCl3 i
s found to be one of the appropriate oxidants to prepare emeraldine, t
hough its standard electrode potential (0.771 V) is lower than that of
(NH4)2S2O8 (1.94 V) which has been conventionally used to prepare eme
raldine.