Poly(aniline-co-o-toluidine) and poly(aniline-eo-m-toluidine) have been synthesized by both chemical and electrochemical copolymerizations of aniline with o-toluidine and with m-toluidine, respectively. The compositions of the copolymers were determined by 1H NMR spectroscopy and could be altered by variation of the comonomer feed ratios. Thus, conductivity of copolymers can be controlled in a broad range, (e.g. when doped with 1 M HC1), from cá. 10 S/cm for homopolymer of aniline to ca. 0.1 S/cm for those of toluidines. The relationship between copolymer composition and comonomer feed ratio shows that the toluidines are more reactive than aniline in the copolymerization. The results are consistent with the proposed mechanism for the polymerization of aniline and its derivatives.

The resistivity of electrochemically synthesized polyaniline films was measured with the films submerged in electrolyte. The resistivity was found to depend on the redox state of the film, the pH of the solution and, to a lesser extent, on the type of anion present. The resistivity at a given pH is low but only inside a narrow potential window. The width of this window decreases with increasing pH and vanishes at pH 6. The walls of the potential window correlate roughly with the formal potentials of the redox processes as determined by cyclic voltammetry. It has been shown that the resistivity of polyaniline depends on its moisture content. For the wet polymer a small degree of protonation is apparently sufficient to cause a decrease in resistivity of more than 6 orders of magnitude. This behavior may be rationalized by assuming that, in the presence of water, the charge transport mechanism involves proton exchange reactions as well as intermolecular electron transport.

Poly(o-toluidine), poly(m-toluidine), and poly(o-ethylaniline) have been synthesized chemically and electrochemically. The polymers were characterized by elemental analysis, UV-vis spectroscopy, and cyclic voltammetry. Elemental analysis data suggest that the protonated polymers are derived from bases containing ca. 37-54% oxidized (imine) units. Upon treatment with 1 M HC1, conductivities of the polymers increase dramatically from ca. 10~8 S/cm to ca. 1CT1 S/cm for polytoluidines and to ca. 1CT3 S/cm for poly(oethylaniline). The conductivities, UV-vis spectra, and electrochemical reactions of the polymers are compared with those of polyaniline and are shown to be consistent with a reduction in -conjugation of the alkyl derivatives caused primarily by steric effects.

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A convenient method is presented for determining the rate of polyaniline formation in the electrochemical polymerization of aniline in aqueous HC1 solution utilizing cyclic potential sweep techniques. In this method, the mass of polyaniline deposited on a platinum electrode is correlated with the polymer anodic peak current that is recorded during the polymerization. The rates of polymer deposition were therefore monitored by the increases in the anodic peak current at various concentrations of aniline. A kinetic expression obtained for the polymerization accounts well for the autoacceleration process in the electrochemical polymerization of aniline and supports the mechanism of polymerization in which monomeric aniline is incorporated in the growing polymer. IntroductionAmong all of the electrically conductive polymers, polyaniline is a particularly attractive material because it has a moderately high conductivity upon doping with simple Bronsted acids,'J is easily synthesized by chemical or electrochemical oxidation of aniline,24 has well-behaved electrochemistry$vs and has good environmental stability.2 In comparison with extensive studies on the chemical structure, conduction mechanism, polymerization mechanism, and other properties of polyaniline, few systematic investigations on the kinetics of the electrochemical polymerization of aniline have been reported, although such investigations could lead to a better understanding of the mechanism of polymerization reactions.The overall electrochemical polymerization of aniline has been as a bimolecular reaction involving a radical cation intermediate and a two-electron-transfer process for each step of polymerization. Recently, polyaniline deposition and doping charges8-l0 were used as probes to monitor the electrochemical polymerization of aniline by cyclic potential sweep techniques.