Abstract

European Journal of Mass Spectrometry
Volume 12 Issue 5, Pages 301–310 (2006)
doi: 10.1255/ejms.828

A comparison of electrospray-ionization and matrix-assisted laser desorption/ionization mass spectrometry with nuclear magnetic resonance spectroscopy for the characterization of synthetic copolymers

Abdulrahman M. Alhazmi,^a Marie-Soleil Giguère,^a Marc A. Dubé,^b Paul M. Mayer^*,a
aDepartment of Chemistry, University of Ottawa, 10 Marie-Curie, Ottawa, Ontario, Canada K1N 6N5
^bDepartment of Chemical Engineering, Centre for Catalysis Research and Innovation, University of Ottawa

Electrospray ionization (ESI-MS) and matrix assisted laser desorption-ionization (MALDI-MS) were used to determine the composition (monomer ratios) and structure (end group analysis) relative to ¹H NMR spectroscopy and theoretical predictions for three different copolymers: poly(butyl acrylate/vinyl acetate) (PBA/PVAc), poly(methyl methacrylate/vinyl acetate) (PMMA/PVAc) and poly(butyl acrylate/methyl methacrylate) (PBA/PMMA). We found that the ESI results were in excellent agreement with 1H NMR spectroscopy for PBA/PVAc and PBA/PMMA copolymers whereas there was more divergence in the case of PMMA/PVAc. In the case of PBA/PMMA copolymers similar distributions of products were observe by ESI-MS and MALDI-MS with the two major products classes differing by their end-groups. One class has hydrogen and dodecylthio end groups while in the other the dodecylthio has been replaced by α-cyanoisopropyl from the initiator. The relative abundance of these distributions as a function of copolymer conversion for a series of reaction conditions was investigated by both ESI and MALDI. MALDI results consistently underestimated (relative to ESI) the butylacrylate monomer ratio in PBA/PMMA and the abundance of co-polymer oligomers terminated by a dodecylthio group from the chain transfer agent.

Keywords: copolymer; electrospray ionization mass spectrometry (ESI-MS); end-group analysis; matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS); monomer ratio; NMR

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