Electropolymerization of Methylene Blue Investigated Using On-Line Electrochemistry/Electrospray Mass Spectrometry

The initial products of the electrochemical polymerization of methylene blue were studied using a thin-layer flow cell coupled on-line with electrospray mass spectrometry. A potentiostatic technique was applied to initiate the polymerization while the soluble n-mers generated were monitored by mass spectrometry. Methylene blue dimers and trimers were observed at m/z values consistent with either “nitrogen-to-ring” coupling of the monomers or with “ring-to-ring” coupling of demethylated monomers during the electropolymerization. Experiments accomplished in D2O-based solutions prove that “nitrogen-to-ring” coupling is the dominant process.