Characterization of polyaniline doped with diphenyl phosphate

UV–Vis spectroscopy and conductivity of the polyaniline (PANI) doped with diphenyl phosphate (DPHP), in comparison with that of HCl-doped polyaniline, show that the decrease in polaron delocalization and structural order results from the steric hindrance imparted by the longer chain counter ion. PANI protonated with DPHP is soluble in common organic solvents such as toluene, chloroform, dimethyl sulfoxide, etc. The conductivity of PANI/DPHP pressed pellet (at 25°C, 1.66 S cm−1) increases with temperature from −40°C (1.18 S cm−1) to +140°C (3.07 S cm−1) due to thermal activation, and decreases with temperature from 140 to 180°C (0.25 S cm−1) due to thermal undoping accompanied by the loss of some polarons. The temperature dependence of spin density is consistent with those of conductivity. After the heating scan, the conductivity (0.52 S cm−1) at room temperature reduces to nearly one-third of the original value.