Elaboration and characterization of carboxylic acid-functionalized polypyrrole films

• Poly(N-alkylpyrroles) and poly(N-carboxyalkylpyrroles) were synthesized.
• N-substituted polypyrrole films were prepared by anodic electropolymerization.
• Full characterization of substituted polypyrrole films properties.
• Influence of the alkyl chain length and carboxy group on polymer films properties.

Conducting polymers such as polypyrrole and its derivatives are highly attractive for a number of applications including biology, sensing and molecular electronics. For these purposes, poly(N-carboxyalkylpyrroles) are of interest since they contain a terminal carboxyl group that can be easily modified with biological or chemical moieties. In the present study, pyrrole monomers were modified by grafting, on the N-position of the pyrrole monomer, of an alkyl chain, whose length varied from 1 to 10 carbons, terminated by a carboxyl group. The substitution significantly decreased the solubility of the monomers but it was although possible to solubilize them in acetonitrile. So, the anodic oxidation of these N-substituted pyrroles was performed in acetonitrile leading to the electrodeposition of substituted polypyrrole films. The morphological features (topography, thickness, roughness) were determined and compared with the ones of polypyrrole and poly(N-alkylpyrroles) having the same chain length. The morphology of the polymer films was shown to be strongly dependent on the alkyl chain since non-substituted polypyrrole exhibited granular structure when substituted ones had a fibrillar structure. The substitution also significantly impacts on the wettability of the films because an increase of the substituted chain length led to the increase of the hydrophobicity of poly(N-carboxyalkylpyrroles).

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