Structures and properties of the soluble polyanilines, N-alkylated emeraldine bases

The N-alkylated emeraldine bases (N-butyl, N-hexyl, N-octyl, N-decyl, N-dodecyl, and N-hexadecyl) are synthesized by incorporation of flexible alkyl chains onto the polyaniline (PAn) through an N-alkylation method with the emeraldine base. The solubility of PAn in common organic solvents is improved remarkably with the alkylation and the oxidation level is maintained at 40–50 mol% (close to that of the original emeraldine base, 50%) allowing for an adequate acid doping. When carbon number of the alkyl side chain is six or more, the polymers can be dissolved in common organic solvents (such as tetrahydrofuran, dichloromethane, and chloroform) even in the presence of a protonic organic acid as dopant, such as dodecylbenzene sulfonic acid (DDBSA) and camphor sulfonic acid (CSA), and free-standing films can be obtained by casting from the solutions. When the carbon number is 12, the polymer film is flexible. DDBSA-doped N-alkylated emeraldine salt films cast from polymer solutions in dichloromethane in the presence of the acid dopant have maximum conductivities in the range 10−2– 10−4 S/cm, being two to three orders of magnitude higher than those of the reported HClO4-doped poly(N-alkylaniline)s.