AN INVESTIGATION OF ELECTROCHEMICALLY PRODUCED POLYMERS FROM ANILINE AND BITHIOPHENE BY RAMAN-SCATTERING AND IMPEDANCE SPECTROSCOPY

The surface sensitive techniques Raman spectroscopy and impedance spectroscopy were employed to study electrochemically produced polymer films from aniline (PANI) with and without p-phenylenediamine (p-PDA) being added. The Raman spectra of the polymer produced in the presence of the additive (PANI/p-PDA) show sharp bands indicating a uniform microstructure of the deposit, whereas the spectrum of PANI exhibits broad unresolved bands. Also the impedance spectra of PANI/p-PDA exhibit strongly reduced semicircular arcs as compared with the semicircles for PANI indicating a smaller charge-transfer resistance for the modified polymer. Model calculations assuming a fractal structure of the electrode surface suggest that PANI/p-PDA posses a smoother sample surface than neat PANI. For comparison, electropolymerization of bithiophene leads to a product with a sharp Raman signal in agreement with the concept that polymerization of thiophene occurs without branching.