XPS, AFM and electrochemical investigation on the inner composition of insulating poly(o-aminophenol), PoAP, deposited on platinum by CV, as a function of the number of cycles

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