Comparison of ESI, APCI and MALDI for the (tandem) mass analysis of poly(2-ethyl-2-oxazoline)s with various end-groups

A series of poly(2-ethyl-2-oxazoline) (PEtOxs) with various end-groups were analyzed by different mass spectrometry (MS) techniques (electrospray ionization mass spectrometry (ESI-MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS)). In a systematic comparison study the three soft ionization methods (ESI, APCI and MALDI) were exploited to investigate the PEtOxs with regard to their molecular composition, molar masses (Mn and Mw) and polydispersity index (PDI) values. In addition, a detailed characterization via tandem mass spectrometry experiments was performed to gain further structural information about these polymers and their fragmentation patterns. The effect of the end-groups on the fragmentation patterns was investigated for this polymer type. Additionally, the successful interpretation of tandem MS data via a special software was shown for this type of polymer in order to open up this field also for polymer scientists who are not MS-specialists. The insights gained from this work will assist the structural elucidation of a broad range of synthetic polymer classes in the future.