IN-SITU FOURIER-TRANSFORM INFRARED ATTENUATED TOTAL-REFLECTION (FTIR-ATR) SPECTROSCOPIC INVESTIGATIONS ON THE BASE-ACID TRANSITIONS OF LEUCOEMERALDINE

Leucoemeraldine, the reduced form of the polyaniline, was obtained by electrochemical polymerization. Extensive infrared spectroscopic studi es are discussed in this work. Ex situ FTIR spectra measured in NaReO4 /HReO4 electrolytes with different pH-values are presented and the abs orption bands are assigned to different vibrational modes. Additionall y, a distinct picture of the base-acid transition is evaluated using i n situ FTIR-ATR measurements in electrolytes containing the supporting salts KPF6/HPF6, NaClO4/HC1O(4) and NaReO4/HReO4. The results demonst rate that in strong acidic media leucoemeraldine nitrogen atoms can be partly protonated. The protonation process starts in the pH-range 2.5 and 3 in the intercalation of anions from the electrolyte into the po lymer structure is determined semi-quantitatively. (C) 1997 Elsevier S cience Ltd.