Synthesis and chemical properties of photoluminescent self-doped polyanilines

Fluorescent self-doped polyanilines (PAS-AntPy-a and PAS-AntPy-b) were obtained by the pyridinium sulfonation of poly(2-methoxyaniline-5-sulfonic acid) (PAS) with 4-(2-anthracene-9-yl-vinyl)pyridine (AntPy). The degrees of pyridinium sulfonation in PAS-AntPy-a and PAS-AntPy-b were 0.70 and 0.97, respectively. A neutral polyaniline with an AntPy side unit (PANI-AntPy) was synthesized by the oxidative polymerization of N-(2-aminophenyl)-4-(2-anthracene-9-yl-vinyl)pyridinium chloride. The UV-vis spectra of PAS-AntPy-a and PAS-AntPy-b exhibited an absorption due to the polaron band that was derived from the protonation of amine groups in the polyaniline backbone with the remaining sulfonic acid proton. In contrast, PANI-AntPy did not exhibit absorption due to the polaron band. PAS-AntPy-a, PAS-AntPy-b, and PANI-AntPy were photoluminescent in a solution. The electric conductivity of PAS-AntPy-a was σ = 1.5 × 10⁻⁷ S cm⁻¹, which was higher than that of H₂SO₄ doped PANI (4.2 × 10⁻⁹ S cm⁻¹) reported previously.