Transient effects during the electrochemical doping of cis-(CH) x : in situ ESR study

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Abstract
An in situ electron spin resonance (ESR) study has been carried out during the electrochemical doping (n and p type) of cis-(CH)x. Partial cis-trans isomerization was deduced from the observation of two superposed ESR lines at very light doping level (Y ≃ 0.06 %). For Y ≃ 0.3 % a single sharp line was observed suggesting that a state of complete or almost complete isomerization was reached. The diffusion coefficient D of the counterions (dopants) from the surface to the interior of the fibrils has been deduced (D ∼ 5 x 10-18 cm2 s-1). Our results show that this diffusion which is very slow in the volume of the fibrils is not required to trigger the isomerization process. A model is proposed in order to understand this situation taking into account the existing information on the fibril microstructure