Characterization of Styrene/n-Butyl Acrylate Copolymer by Electrospray Ionization-Ion Mobility Spectrometry-Mass Spectrometry

Styrene/n-butyl acrylate copolymer (number average molecular weight: 2700, weight average molecular weight: 6100, polydispersity: 2.3) synthesized by radical polymerization was analyzed by two types of mass spectrometry (MS). In the analysis using matrix assisted laser desorption ionization-MS, signals were observed up to a molecular weight of about 5000. On the other hand, in the analysis using electrospray ionization-ion mobility spectrometry-MS (ESI-IMS-MS), signals were observed up to a molecular weight of about 9000 (m/z 2200 in charge number of 4 from the IMS distribution). Extracted MS spectra obtained from ESI-IMS-MS were analyzed by Kendrick mass defect plot. Copolymer compositions (both terminal structures derived from the initiator, which can be produced by the recombination reaction) could be analyzed up to a molecular weight of 7800. This range corresponds to about 80 % of the copolymer molecular weight distribution measured in size exclusion chromatography using polystyrene standards. It was confirmed that ESI-IMS-MS is more effective for the analysis of synthetic polymers with high polydispersity.