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 (M_n and M_w) 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.