IN-SITU FTIR-ATTENUATED TOTAL-REFLECTION SPECTROSCOPIC INVESTIGATIONSON THE BASE-ACID TRANSITIONS OF POLYANILINE - BASE-ACID TRANSITION INTHE EMERALDINE FORM OF POLYANILINE

Emeraldine refers to the semi-oxidized state of polyaniline and it can exist in the base form or the protonated form (salt) generated by tre atment of the base form with an acid. Using a newly applied doping sys tem NaReO4/HReO4, the investigation of the base-acid transition proces s of emeraldine has been carried out by ex situ and in situ FTIR spect roscopic methods. In situ FTIR-ATR (attenuated total reflection) measu rements performed during the base-acid transition process clearly show the change in the structure of the polymer film observable. The physi cal properties of emeraldine can be changed considerably by varying th e pH of the media. The base form of emeraldine is an insulator and tre atment with acidic media results in the highly conducting salt form (p roton doping). The protonation of emeraldine starts at pH 6. The inten sity of a broad absorption band at wavenumbers higher than 2000 cm(-1) (0.25 eV) depends strongly on the pH of the electrolyte. This absorpt ion band bleaches completely with increasing pH, indicating a strong c orrelation between this band and the metallic character of the polymer . On the basis of in situ FTIR-ATR measurements, a reaction path of ac id-base transitions has been proposed.