Characterization of self-doped conducting polyanilines bearing phosphonic acid and phosphonic acid monoester

Novel self-doped polyanilines bearing phosphonic acid, poly(2-methoxyaniline-5-phosphonic acid) (PMAP) and poly(2-methoxyaniline-5-phosphonic acid monoethyl ester) (PMAPE) were characterized in the following properties: (1) thermostability, (2) morphology in the solid state, (3) absorption and transparency in the spin-coating film, (4) delocalization of polaron, (5) doping efficiency, and (6) chemical oxidation and reduction. The UV–vis–NIR absorption spectra of the spin-coating films of PMAP/pyridine (1:2) and PMAPE/pyridine (1:1) show the polaron band and free carrier tail, which are characteristic to the conducting polymers. The highly transparent films of them (up to ∼90% transparency) were formed by spin-coating. Concerning the property of the polaron in the polymer, the ESR spectra suggest that polaron of PMAP/pyridine (1:2) is more delocalized than that of PMAPE/pyridine (1:1). The XPS experiments indicate that the doping efficiency of PMAP is much higher than that of PMAPE, which is likely to be due to diprotic acid units derived from phosphonic acid of PMAP. Oxidation and reduction of PMAP and PMAPE were demonstrated by treatment with the corresponding oxidant {(NH4)2S2O8} and reductant (N2H4·H2O), respectively.