THERMAL AGING OF ELECTRICALLY CONDUCTING POLYMERS - XANES MEASUREMENTS OF POLYTHIOPHENES

The thermal ageing of polythiophenes was investigated by X-ray absorpt ion spectroscopy. XANES (X-ray absorption near edge structure) measure ments at the sulfur K-edge and the phosphorus and chlorine K-edges res pectively are used to monitor main chain modifications and counter-ion degradation during baking. The electrochemically synthesized polythio phenes were modified by group substitution of the polymer backbone and the counter-ions were also varied for each polymer. After heating to 80 degrees C, absorption spectra were taken at temperatures varied in steps of 10 degrees C up to 170 degrees C. The comparison of the spect ra of the heated polymers with those of model compounds proves that th ermal stress causes counter-ion degradation in all polymers investigat ed here. Polymer chain variations decrease with increasing size of alk yl-side chains on the thiophene backbone.