End-Group Analysis of Methacrylic (Co)polymers by LC-ESI-MS2

End-group analysis was achieved on poly(methyl methacrylate) and poly(methyl methacrylate- r -butyl acrylate) by liquid chromatography−electrospray ionization−ion trap mass spectrometry (LC-ESI-IT MS) and electrospray ionization−Fourier transform ion cyclotron resonance tandem mass spectrometry (ESI-FTICR MS 2 ). The two polymers were produced by radical polymerization in butyl acetate at relatively high temperature using the same initiator, tert -butylperoxy-3,5,5-trimethylhexanoate. In both polymers, structures with different end-groups were successfully assigned using gradient elution LC-IT MS, with the aid of exact mass experiments in an FTICR MS instrument. Isobaric materials in PMMA were discriminated using accurate mass FTICR MS 2 . Isocratic LC-MS reduced the complexity of the data of P(MMA- r -BA), made the attribution of peaks easier, and shortened the experimental time compared to gradient elution LC-MS. The identification of end-groups in both the methacrylic homo- and copolymer demonstrated that β-scission and radical transfer to solvent play an important role in the polymerization.