The analysis of conducting polymers by electrospray Fourier transform mass spectrometry. Part I: Ionene polymers

The analysis of synthetic 6-2, 6-3 and 6-4 ionene polymers by electrospray ionization Fourier transform mass spectrometry (ESI-FTMS) is reported here. This is the first in a series of papers on the analysis of conducting polymers utilizing soft ionization techniques, thus allowing for the analysis of intact molecular ions. The syntheses of these individual polymers result in a variety of compounds with different molecular structures which are related to the normal linear ionene polymer. While the mechanisms by which the 6-2 and the 6-3 ionene polymers are synthesized are very similar, the synthesis of 6-4 ionene proceeds differently. In addition, the presence of a gas-phase bromide ion salt-bridged to the backbone of the polymer chain is observed in the resulting mass spectra, as well as the possibility of intramolecular cyclization. The latter has been proposed previously. This cyclization process becomes more possible as the number of methylene groups in the linking chain increases. Finally, we observed that the presence of a bromide ion in the sample helped the interpretation of sustained off-resonance irradiation collisionally-activated dissociation (SORI-CAD). Based on the isotopic pattern provided by the halogens, a "built-in" label which can be traced from the fragment ions back to the parent ion peak is found to be useful in structural assignments.