Post-Polymerization Electrochemical Functionalization of a Conducting Polymer: Diazonium Salt Electroreduction at Polypyrrole Electrodes

Abstract

In this paper we report the functionalization of conductive polypyrrole (PPY) films via electrochemical reduction of the aryl diazonium salts in a manner that is similar to the one employed for other conductive surfaces. To understand the general trends of the grafting behavior of diazonium salts and to establish the optimal conditions for the covalent functionalization of the PPY films, we have compared the grafting behavior of four p-substituted phenyldiazonium salts: p-nitrophenyl diazonium tetrafluoroborate (PNBDBF 4 − ), p-tolyl diazonium tetrafluoroborate (TDBF 4 − ), p-fluorophenyl diazonium tetrafluoroborate (FPDBF 4 − ) and 4-diazo-N,N-dimethylaniline tetrafluoroborate (DDMABF 4 − ). The selection of the molecules to be grafted was done both for their electroactivity after grafting and the contrasted electronegativityof the substituents at the benzene ring. For all investigated diazonium salts, a linear relationship between their reduction potential at the PPY electrodes and Hammett substituent constants was obtained, suggesting a similar electrochemical reaction mechanism. The functionalization of the polypyrrole films has been evaluated using electrochemical methods like EQCM, CV and EIS. The presence at the polymeric films surface of the functional groups introduced by the electrochemical reduction of diazonium salts was evidenced also by XPS. This approach enables new functionalities on PPY that could otherwise not withstand the polymerization conditions.

Synthesis of conducting azopolymers by electrochemical grafting of a diazonium salt at polypyrrole electrodes

“…As reported in our previous study concerning several parasubstituted arenediazonium salts [10], also in the case of NABDBF 4 À the reduction at the polypyrrole electrode occurs more easily (E p approx. +0.1 V) than at the other electrodes (E p approx.…”

“…This represents a confirmation of our previous results discussed in ref. [10] which concern the electrochemical functionalization of polypyrrole with para-substituted phenyl groups via diazonium chemistry.…”

“…Our previous attempts in this direction involved the direct modification of unsubstituted polymers, such as polypyrrole [10].…”

XPS and ATR‐FTIR study on chemical modifications of cold atmospheric plasma (CAP) operated in air on the amino acids L‐proline and trans‐4‐Hydroxy‐l‐proline

“…Possible atoms for this new compound in the working gas air are nitrogen and oxygen. According to various studies investigating different CNO bonds, we conclude that the new N1s peak can be attributed to either or NO 2 …”

The Role of Aryldiazonium Chemistry in Designing Electrochemical Aptasensors for the Detection of Food Contaminants

“…However, several studies revealed that the substituent in the para - position has a strong influence on the proneness for spontaneous grafting, and salts with electron-withdrawing substituents are able to spontaneously graft even onto less-reducing substrates, such as carbon [ 132 , 161 ]. Among the different functionalization methods, the electrochemical reduction of aryldiazonium salts is the most popular since it allows a higher degree of derivatization control, and the process is straightforward and expeditious [ 36 , 131 , 161 , 162 , 163 , 164 , 165 ]. The potential of the characteristic diazonium electroreduction peak evidenced in cyclic voltammograms (CVs) is useful for assessing diazonium reactivity, as it is directly influenced by the nature of substituents on the aromatic ring [ 132 , 141 , 161 , 163 , 164 , 165 , 166 , 167 ].…”