Structural modifications during conducting polymer formation — an ellipsometric study

Abstract

Polyaniline films potentiodynamically synthesised on gold substrates are analysed ex situ by conventional and imaging ellipsometry (at constant wavelength). Polymers grown up to 50 cycles appear to be homogeneous, whereas different structures are displayed by thicker layers. The memory effect, induced by the polymer electrochemical characterisation, in subsequent polymer growth, is demonstrated. In the case of thin films, a reliable methodology has been successfully employed to obtain, from the ellipsometric parameters Z and , the refractive index, the extinction coefficient and the thickness of polymer layers. This approach also allowed us to quantitatively evaluate the magnitude of polymer swelling upon oxidation (11-22%). Furthermore, the surface morphology is well evidenced by the results obtained by imaging ellipsometry.

Electropolymerization of 3-methylthiophene studied by multiflux convolution

“…The simultaneous determination of optical and electrochemical parameters such as photocurrent [9] and exsitu, in-situ and imaging ellipsometry as a function of the potential/current [10,11] or of the growth charge [12,13] has proven helpful in describing the electropolymerization process. Several steps in the electrodeposition of poly(3-methylthiophene) (P(3-MeTh)) have been reported based on these techniques and supported by SEM and AFM information [14][15][16].…”

Improved Potentiometric and Optic Sensitivity of Polyaniline Film to Dissolved Oxygen by Incorporating Iron‐Porphyrin

“…The optical data obtained during this characterization gives us important information about the maximum range of grayscale values which can be obtained with the modified electrode and indicates the optimal potential range for DO detection. Figure 4 B shows a hysteresis between the anodic (forward) and cathodic (backward) scans, which can be attributed to the structural and morphologic modifications that all conducting polymers suffer during their redox processes 32,35,36; Since the redox conversion of any polymer film involves mechanical deformation of the matrix (with simultaneous intake and/or expulsion of solvent and counter‐ions), high activation overpotentials are required both for oxidation as well as for reduction, resulting in a significant redox hysteresis. In the absence of oxygen the grayscale values are at a maximum when the modified electrode is in its reduced state.…”

An ellipsometric study of poly(3,4-ethylenedioxythiophene) electrosynthesis – from the initial stages to thick layers formation

“…Ellipsometric investigations on the electropolymerization of other thiophene derivatives from organic media, revealed the occurrence of structural polymer modifications upon thickening [21,27,28], feature that has also been observed for other ECP [29][30][31]. Thus, the homogeneous or heterogeneous character of PEDOTh film prepared from non-aqueous solution is a open question.…”