Lewis acid doped polyaniline. Part II: Spectroscopic studies of emeraldinebase and emeraldine hydrochloride complexation with FeCl3

It is demonstrated that Lewis acid doping of polyaniline in the oxidation s tate of emeraldine can be conveniently monitored by Fe-57 Mossbauer spectro scopy if FeCl3 is used as the dopant. The spectrum of doped polyaniline con sists of two doublets with distinctly different Mossbauer parameters which can be unequivocally ascribed to two types of complexing sites (amine and i mine nitrogens). From the temperature dependence of the isomer shift and th e recoil free absorption, we have calculated Mossbauer lattice temperature Theta(m)' as probed by both complexing sites, which were 83 K for the amine and 126 K for the imine sites. These low values of Theta(m)' imply signifi cant; mobility of the dopant at temperatures close to room temperature, whi ch is typical of small molecules inserted into polymer matrices. FeCl3-dope d polyaniline is soluble in nitromethane, and acetonitrile and films cast f rom these solvents show conductivity of 0.2 S/cm. FeCl3-doped polyaniline i s also a strong near-infrared absorber.