Analytical Characterization of Poly(Pyrrole‐3‐Carboxylic Acid) Films Electrosynthesised on Pt, Ti and Ti/Al/V Substrates

Abstract

With the aim of developing a polymeric multilayer film for application in advanced biomaterials, as a first step poly(pyrrole-3-carboxylic acid) films (abbreviated as PPy-3-carbox) were electropolymerised from pyrrole-3-carboxylic acid solutions by cyclic voltammetry and chronoamperometry on platinum, titanium and Ti90Al6V4 substrates and characterised both electrochemically (cyclic voltammetry) and spectroscopically (X-Ray Photoelectron Spectroscopy, XPS). Electrochemical experiments showed that the potential range adopted for electropolymerization affects the polymer electroactivity, by analogy with unsubstituted polypyrrole. The combination of conventional and chemical derivation-XPS provided information on PPy-3-carbox surface structure, showing no significant difference between films grown on different substrates and an increase of the COOH groups amount (one group over three pyrrole rings, as an average) with respect to unsubstituted polypyrrole (PPy), as expected. Finally, a preliminary Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) investigation was performed in order to get further information on the polymer structure and electroactivity.

Surface (XPS, SIMS) chemical investigation on poly(pyrrole-3-acetic acid) films electrosynthesized on Ti and TiAlV substrates for the development of new bioactive substrates

“…31,40 Comparison with spectra of PPy-3-acetic, in contrast to that observed for PPy-3-carboxylic film, 31 showed no remarkable differences. In both polymers the second peak in the fitting (peak B) was adopted as a binding energy (BE) reference (284.8 eV) because the contaminant carbon peak was found to overlap with the pyrrole C˛component.…”

“…This finding leads to the conclusion that the presence of an acetic group does not induce a BE shift on theˇ0-atoms of the pyrrole ring, in contrast to that observed in the case of PPy-3-carbox, where the COOH group led to a positive BE shift onˇ0 as well as on all atoms of the pyrrole ring. 31 Actually, the presence of a CH 2 group between the pyrrole ring and the carboxylic functionality suppresses the inductive effect of the latter on theˇ0-carbon. As far as the CH 2 COOH and CH 2 COO carbons are concerned, no literature data were available to evaluate their BE values.…”

“…In a previous work, 31 the electrosynthesis and characterization of poly(pyrrole-3-carboxylic acid) (PPy-3-carbox) on titanium substrates was accomplished. A spectroscopic investigation performed by XPS coupled to a chemical derivatization reaction for COOH groups showed that, on average, only one ring over three along the PPy-3-carbox chains bears a carboxylic functionality.…”

“…Therefore,ˇ-substitution has little effect on the electrochemical properties of the aromatic nucleus, in contrast to that observed in the case of pyrrole-3-carboxylic acid, whose oxidation peak was shifted towards more positive potentials. 31 Pyrrole-3-acetic acid oxidation seems to be totally irreversible, because no peak related to the reduction of the oxidized monomer can be recorded after reversing the potential scan; however, a redox couple can be observed already after the first voltammetric cycle, at potential values much lower than that of monomer oxidation. The increase of the relevant peak intensities upon cycling suggests that this couple is related to the deposition of an electroactive polymer.…”

Characterization of soluble oligomers produced by electrochemical oxidation of o‐phenylenediamine by electrospray ionization sequential mass spectrometry

“…We have recently undertaken a systematic spectroscopic and electrochemical investigation9,10 of the structure of PPD obtained under different pH conditions (from 1–7), to complement previous studies (see Ref. 9 for literature references on PPD characterization), generally involving PPD electrosynthesized at very low pH, and to establish structure‐property relationships for the material as a function of polymerization pH.…”