Role of anions in the polymerization of 2,5-dimethoxyaniline in the presence of poly (styrene sulfonic acid)

Poly(2,5-dimethoxyaniline) (PDMA)-Ag composites were successfully obtained through the oxidative polymerization of 2,5-dimethoxyaniline in poly(styrene sulfonic acid) with CH₃SO₃Ag and AgNO₃ as oxidants. In situ ultraviolet-visible spectroscopy results showed that the growth rate of PDMA was strongly affected by CH₃SO₃ ^- and NO₃^-. The coupling reaction of PDMA and NO₃^- was proposed to explain the lower growth rate of PDMA with AgNO₃ as the oxidant in comparison with CH₃SO ₃Ag. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to validate the proposed coupling reaction through the monitoring of the side products and oxidized state of PDMA. The results showed that there were more side products and lower oxidized states for the composite structure in the presence of NO₃^- than in the presence of CH₃SO₃^-, and this agreed with the proposal. Transmission electron microscopy showed that the Ag nanoparticles had almost the same size, regardless of the anions.