Previous investigations on o‐aminophenol (oAP) electropolymerization by cyclic voltammetry (CV), onto platinum, in aqueous solution (phosphate buffer) at neutral pH, have shown the reproducible formation of an insulating film of inherent adherence and thinness, poly(o‐aminophenol) (PoAP). The applicability of this produced film as a permselective membrane for biosensors was demonstrated, as well as the influence of the platinum surface state on its self‐limited growth and morphology. Based on these findings, we have continued our investigation on insulating PoAP by combining compositional (XPS) and electrochemical (CV) analyses. To evaluate the finite film on its compositional homogeneity and stability, we have highlighted, in turn, different analyzed depths by angle‐resolved XPS, repeated experiments and performed stability test in ultra‐high vacuum. This investigation, combined with an accurate curve‐fitting procedure, has allowed the estimation of the PoAP thickness and the assignment of chemical states for determining its polymerization sequence. We show that PoAP thickness is about 7 nm; its repeat formula comprises alternating quinoneimine and oAP units, including approximately one water molecule, and the polymer chains are terminated with carbonyl‐type groups. Copyright © 2014 John Wiley & Sons, Ltd.

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The finite electrosynthesis, requiring 20 voltammetric cycles at neutral pH, of insulating poly(o-aminophenol) (PoAP)and its polymerization mechanism and chemical structure up to the outermost surface were reported in previous work. By reducing the number of voltammetric cycles, XPS, atomic force microscopy, and electrochemical experiments were here confined to partially grown PoAP to better understand the role of the platinum surface on the initial adhesion mechanism and polymer growth. XPS results from reduced number and conventional 20 cycles show that PoAP composition is the same at any cycle. The main differences imaged by atomic force microscopy between 1, 5, and 20 cycles are on the amount of 'small-sized particles' adsorbed on platinum prone to 'fill' the empty sites. The progressive filling of the platinum sites with cycles was also proved by electrochemical test with potassium-ferricyanide. These new results add valuable information, which sustain previous hypotheses on the growth process of PoAP chains, their composition, and lateral alignment. Some questions, concerning the identification of PoAP anchoring bonds on platinum, lateral H-bonds with water, and inter-chains interactions, still remain unanswered and will be further addressed by the employment of new advanced means of investigation already in progress.

Previous XPS investigations of insulating poly(o‐aminophenol) (PoAP), electrosynthesized by cyclic voltammetry on Pt substrates, revealed the formation of a thin film of about 7 nm of thickness, firmly adherent onto the electrode surface and stable even under Ultra High Vacuum (UHV) conditions. A constant repeat formula made of alternating quinoneimine and monomer units was derived with polymer chains terminating as carbonyl‐type groups. Based on these findings, we have continued our investigation on insulating PoAP by employing time‐of‐flight SIMS whose superior surface sensitivity is well‐known. The aim was to corroborate the polymer structure with particular reference to the top surface layers in view of possible bio‐applications and to understand the possible way of interaction with the underlying platinum electrode surface. In order to do this, we analyzed PoAP films grown at different levels of the electrochemical synthesis (1, 5, and 20 scan cycles) and the platinum substrate itself. The individuation of the main characteristic fragments and the behavior of their intensity by varying the stage of the electropolymerization allowed to confirm the polymer structure and the presence of terminating carbonyl groups. Remarkably, from the analysis of the PoAP/Pt interface at the early stage of the polymer formation, it was possible to discern that polymer chains tend to interact with the electrode surface preferentially by the nitrogen atom of the oxidized monomers. Copyright © 2016 John Wiley & Sons, Ltd.