FRACTIONATING VACUUM THERMAL DEPOSITION OF POLYANILINE FILMS - EFFECT OF POSTDEPOSITION ACID-BASE TREATMENT

Vacuum thermal evaporation of a single portion of chemically synthesized polyaniline (PAN) base powder was performed step-by-step within four temperature intervals in the 240-450-degrees-C range. The vapour was deposited on quartz and SnO2-glass substrates, each fraction being deposited on a separate substrate. The samples obtained were subjected to cyclic contrast acid-base treatment, and UV-Vis spectra of the fractions after each treatment cycle were registered. The spectra of the as-deposited fractions appear to have little in common with conventional PAN spectra. The appearance of absorption bands essential for conventional PAN spectra is found to occur for some of the fractions only after the above treatment. This is apparently due to recombination of PAN oligomer radical fragments, formed in the course of the evaporation, resulting in restoration of PAN macromolecule structure. The recombination may be intensified by conformational changes during the acid-base treatment. Cyclic voltammetry curves for the most PAN-like fractions resemble the ones for conventional PAN.