Role of electrolyte/polymer interface on the quantitative interpretation of in‐situ ellipsometry of electroactive polymer films

A new in‐situ ellipsometric procedure has been used for determination of the optical properties and thickness of polyaniline films as a function of. the redox state in sulphuric and p‐toluenesulfonic acids. The results could be interpreted successfully only when the optical properties of the electrolyte/polymer was considered variable with the redox state. Most probably for the first time, the study shows, that the apparent refractive index of electrolyte varies with the redox state in a similar manner to the optical properties and thickness of the polymer film. In this case, for all calculations a one layer model was sufficient. The origin of such observation is attributed to the change in electrolyte composition at the polymer surface and heterogeneity of the film when oxidized.