Mass spectrometry and ion mobility study of poly(ethylene glycol)‐based polyurethane oligomers

Abstract

Rationale Commercial‐grade polymer synthesis is performed via melt polymerization, which leads to polydispersion. The work reported herein provides a synthetic strategy to produce mono‐dispersive polyurethane oligomers and an analytical strategy to distinguish these oligomers, providing chemists with the tools necessary to synthesize and identify specific polymer structures that exhibit a desired property. Methods Three isomeric poly(ethylene glycol)–polyurethane (PEG‐PUR) oligomers were synthesized and analyzed via flow‐injection ion mobility mass spectrometry (IM‐MS). Each polymer oligomer was injected and run independently via flow injection at 100 μL•min−1 and analyzed in positive ion mode on a drift tube quadrupole time‐of‐flight (QTOF) instrument. Mobility measurements were determined using a single‐field approach. For tandem mass spectrometry (MS/MS) experiments, the sodium‐adducted singly charged precursor ion was isolated in the quadrupole and subjected to a range of collision energies. Results In MS experiments, both +1 and +2 sodium‐adducted species were observed for each oligomer at m/z 837.4 and 430.2, respectively. When isolated and fragmented via MS/MS, the +1 precursor yielded distinct product ions for each of the three isomeric oligomers. Fragmentation generally occurred at urethane linkages via 1,3‐ and 1,5‐H shift mechanisms. IM was also used to distinguish the three isomers, with greater IM separation observed for the +2 versus the +1 species. Conclusions Mono‐disperse PEG‐PUR oligomers were synthesized and analyzed. Although the polymeric oligomers analyzed in this study are quite small and structurally simple, this work serves as a model system for the synthesis and structural characterization of larger, more complex block copolymers.

Noncovalent Host–Guest Complexes of Artemisinin with α-, β-, and γ- Cyclodextrin Examined by Structural Mass Spectrometry Strategies

“…Few individual studies exist of unbound artemisinin and cyclodextrins explored by IM-MS. , This is the first report, of which we are aware, utilizing IM-MS for structural studies of ART:CD combination therapies. In addition to IM-MS measurements, computational modeling has been used to investigate theoretically derived gas-phase structural conformations of molecules using several developed CCS calculation algorithms to interpret the IM-MS-derived structural data. − Examples of the molecular diversity investigated through a combination of theoretical and IM-MS approaches include small molecules, synthetic polymer isomers, metal complexes, and nonapeptides. − High-level theoretical models have been used to model individual CDs with various cations. − These studies demonstrate cation preference to orient at the narrower opening of the CD cavity. Therefore, the cation preference for each CD is limited to the size of the narrower opening.…”

Ion mobility mass spectrometry as a powerful tool to analyze complex macromolecular systems

“…In particular, poly (ethylene glycol) (PEG) and poly (propylene glycol) (PPG) (Figure 6.1) have been shown to be extremely well suited for ESI-IMMS analysis and used as exemplary systems multiple times. 24,31,37,75,86,[134][135][136] Therefore, to show the effectiveness of Equation 5.14 and 5.21, they were in a first study applied to IMMS data of PEG and PPG. In Figure 6.2 a mass spectrum of a PEG sample with a nominal molar mass of M w = 3 000 g mol −1 (top) and the corresponding ion mobility mass spectrum showing the separated species (bottom) are shown.…”