A piezoelectric spectroelectrochemical study on the structural interconversion for poly（o-phenylenediamine） between its ladder structure with phenazine units and polyaniline-like chains

The combination of reflectance UV-Vis spectroelectrochemistry with electrochemical quartz crystal microbalance （EQCM） and separate reflectance FTIR characterization were used to investigate the structural interconversion for poly（o.phenylenediamine） （PoPD） between its ladder structure with phenazine units and polyaniline-like linear chains. The poly（o-phenylenediamine） films potentiostatically （0.8 V vs. SCE） grew on Au electrodes from 0.20 mol·L^-1 H2SO4 （PoPD1） or 0.40 mol·L^-1 NaOH （PoPD2） aqueous solution containing 0.20 mol·L^-1 Na2SO4 ＋ 0.10 mol·L^-1 o-phenylenediamine. By considering the mass of deposited PoPD2 film obtained from the EQCM data and the charge consumed under the current peak at ca. 0.6 V vs. SCE for oxidation of -NH2 groups in as-prepared PoPD2 during potential cycling in 0.10 mol·L^-1 aqueous H2SO4, the molar percentage of the polyaniline-like chains was estimated to be 19% （relative to total phenylenediamine units）, being in agreement with the result obtained from a formaldehydecombination experiment through the aminocarbonyl reaction. After 40-cycle potential sweeps between 0.2 and 0.8 V vs. SCE the polyaniline-like chains in PoPD2 could be completely converted via intramolecular cyclization into the ladder structure with phenazine units. However, PoPD1 was found to be perfectly composed of the ladder structure with phenazine units, and after 40-cycle potential sweeps between -0.4 and 0.1 V vs. SCE only 2.5% in molar percentage of PoPD＇s ladder structure could be converted into polyani line-like chains, suggesting that the ladder structure with phenazine units is thermodynamically more stable due to its possessing higher conjugation.

A piezoelectric spectro-electrochemical study on the structural interconversion for poly(o-phenylenediamine) between its ladder structure with phenazine units and polyaniline-like chains

The combination of reflectance UV-Vis spectroelectrochemistry with electrochemical quartz crystal microbalance (EQCM) and separate reflectance FTIR characterization were used to investigate the structural interconversion for poly(o-phenylenediamine) (PoPD) between its ladder structure with phenazine units and polyaniline-like linear chains. The poly(o-phenylenediamine) films potentiostatically (0.8 V vs. SCE) grew on Au electrodes from 0.20 mol.L^-1 H₂SO₄ (PoPD₁) or 0.40 mol.L^-1 NaOH (PoPD₂) aqueous solution containing 0.20 mol.L^-1 Na₂SO₄ + 0.10 mol.L^-1 o-phenylenediamine. By considering the mass of deposited PoPD₂ film obtained from the EQCM data and the charge consumed under the current peak at ca. 0.6 V vs. SCE for oxidation of -NH₂ groups in as-prepared PoPD₂ during potential cycling in 0.10 mol.L^-1 aqueous H₂SO₄, the molar percentage of the polyaniline-like chains was estimated to be 19% (relative to total phenylenediamine units), being in agreement with the result obtained from a formaldehydecombination experiment through the aminocarbonyl reaction. After 40-cycle potential sweeps between 0.2 and 0.8 V vs. SCE the polyaniline-like chains in PoPD₂ could be completely converted via intramolecular cyclization into the ladder structure with phenazine units. However, PoPü₁ was found to be perfectly composed of the ladder structure with phenazine units, and after 40-cycle potential sweeps between-0.4 and 0.1 V vs. SCE only 2.5% in molar percentage of PoPD’s ladder structure could be converted into polyani line-like chains, suggesting that the ladder structure with phenazine units is thermodynamically more stable due to its possessing higher conjugation.