A Comparison of Electrospray Ionization and Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry with Nuclear Magnetic Resonance Spectroscopy for the Characterization of Synthetic Co-Polymers

Abstract

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 One class has hydrogen and dodecylthio end groups while in the other the dodecylthio has been replaced by alpha-cyanoisopropyl from the initiator.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.

Photocrosslinking of a novel α,ω‐unsaturated copolyamide: mass spectrometric study on model compounds with benzophenone as photoinitiator

“…Mass spectrometry using soft ionization techniques such as matrix‐assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) has proved to be a powerful analytical tool for the structural characterization of synthetic polymers 1–5. These techniques, and more particularly ESI, can also be applied for the analysis of smaller compounds (monomers and/or oligomers) which will constitute the ultimate polymers.…”

Matrix effects on copolymer quantitation by matrix‐assisted laser desorption/ionization mass spectrometry

“…To stop the reaction at a given time, the ampoules were transferred to an ice bath. Solvent was evaporated at room temperature and atmospheric pressure, and the low molecular weight polymer dried under vacuum for 12 h. 13 Oligomers of molecular weight up to 2000 were produced. A polymerization simulator was used to predict the results of free radical polymerization and thus to determine appropriate reaction conditions (monomer, initiator and chain-transfer agent concentrations) to produce the desired product average molecular weight.…”

Funktionelle Polymere mittels kontrollierter Polymerisationstechniken: Von der Massenspektrometrie endfunktionalisierter Polymere und den mechanischen Eigenschaften photovernetzbarer Blockcopolymere

“…Mit der MS kann die Zusammensetzung einzelner Polymerketten auf molekularer Ebene bestimmt werden. [20,21]…”

“…[15][16][17] Die Massenspektrometrie wird zur Bestimmung der Molmassenverteilung, der Endgruppen und der Zusammensetzung einzelner (Co)Polymerketten verwendet. [18,20,21,163] Dabei ist die MS wesentlich sensitiver als die GPC, die Infrarot-und die NMR-Spektroskopie. MALDI-Massenspektren weisen jedoch oft ein schlechtes S/R-Verhältnis auf, vor allem wenn eine gute Massenauflösung gefordert ist.…”

“…[18,19] Die Massenspektrometrie hat zudem den Vorteil, dass aufgrund der hohen Massenauflösung einzelne Polymerketten voneinander unterschieden und sogar deren Endgruppen und molekulare Zusammensetzungen mit nur einer Analysemethode bestimmt werden können. [20,21] Die Ionisierung der Polymerketten erfolgt aufgrund fehlender basischer Seitengruppen in der Regel durch die Adduktbildung mit Metallionen. In der ESI-MS treten mit zunehmender Kettenlänge mehrfach geladene Ketten durch Anlagerung mehrerer Kationen auf.…”