The expanding role of mass spectrometry as a tool for polymer chemistry

Innovations to mass spectrometry (MS) ionization sources and mass analyzers have helped usher in a new era in polymer chemistry in which the mass spectrometer is viewed as an essential tool that complements classical methods of polymer characterization. MS can be employed for the direct characterization of individual molecules, enabling not only determination of molecular mass and molecular mass distributions, but also determination of structural aspects of polymers such as end-group composition, repeat unit composition and sequence, and the presence of impurities and unintended side products. Here, we review some particular challenges faced for polymer characterization by MS. Synthetic polymers are polydisperse and require fractionation to reduce the complexity of samples analyzed by MS. Different approaches integrating gel permeation chromatography (GPC) with MS analysis for this application are compared and discussed. Next, several different MS methods for characterizing polymer repeat unit and/or end group composition are reviewed, and how this structural discovery process can lead to new directions in synthesis. Finally, recent efforts to process seemingly intractable polymers for MS analysis are described.