The heterogeneous growth of P(3MeTh)—an ellipsometric study

Abstract

Successive thicker P(3MeTh) layers are analysed by ex situ conventional and imaging ellipsometry. Thin films display a smooth surface, are compact and homogeneous while for a growth charge above 20 mC cm − 2 the polymer structure modifies to a still uniform but less dense layer. A two-layer model is used and a mathematical procedure is developed to obtain, simultaneously, from the experimental ellipsometric parameters, Z and c, the thickness and the complex refractive index of P(3MeTh) films grown up to 80 mC cm − 2 . Thicker polymer layers are disordered and present a high degree of surface roughness.

Electropolymerization of 3-methylthiophene studied by multiflux convolution

“…The polymer so obtained displays the characteristic [13,27] redox behaviour of P(3-MeTh), Fig. 2, with an oxidation peak at 0.68 V and two reduction waves at 0.60 and 0.25 V. From the charges involved in polymer oxidation (Q ox ) and reduction (Q red ), the redox conversion reversibility has been evaluated as Q ox /Q red = 1.10; from the electropolymerisation efficiency, Q ox /Q g = 11% and taking into account Eq.…”

“…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

“…It is worth of notice that this feeble modification of the surface can be perceived by the TIRIE optical monitoring of the electrode (Figure 2 B). In the backward potential scan, a cathodic wave with an onset potential of E ≈200 mV (vs. SCE) and centred at E ≈−100 mV (vs. SCE) must be attributed to the presence of FeTSPP in solution since it did not occur during the polymerization of aniline on gold in the absence of the metal‐complex 11,32. The thickening of the film upon repetitive potential cycling is evidenced by the continuous increase of the height of the polymer redox peaks in the potential range −100 to 300 mV (vs. SCE).…”

“…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.…”