IN-SITU FTIR STUDIES ON THE REDOX PROPERTIES OF POLY(THIOPHENE-3-METHANOL) IN PF6- AND CLO4- ELECTROLYTES

In order to gain more information on the role of charge compensating a nions, the C-O-C coupled monomer units and the free CH2OH substituents in the oxidation process of electrosynthesized poly(thiophene-3-metha nol) (PTOH), in situ external reflectance FTIR spectra were recorded d uring the oxidation and reduction of PTOH/ClO4 and PTOH/PF6 films. The voltammetric results indicate a strong memory effect with regard to t he anion used in the synthesis of PTOH. Nevertheless, both PTOH/ClO4 a nd PTOH/PF6 films show similar features in the infrared. The IR spectr a of the oxidized films are characterized by electronic absorption and enhancement of some vibrational modes due to coupling of the movement of the charge carriers with the polymer lattice vibrations. In additi on, bipolar carbonyl bands and bands due to intake of anions are obser ved. The asymmetric stretching band of ClO4- ions inside the film was found to shift about 15 cm(-1) from its value in solution, indicating an interaction between this anion and the polymer lattice. The spectra registered from successive oxidation and reduction steps of PTOH show bands due to the formation of C-O-C bonds, which confirms our hypothe sis of an EC type of oxidation of PTOH. It is shown that the volume ch anges of PTOH films during charging and discharging can be followed by FTIR spectroscopy.