End group analysis of poly(methyl methacrylate) using MALDI-TOFMS and GC-TOFMS
MSTips No. 404
Mass spectrometry can be used to analyze synthetic polymers, providing a variety of information, such as the main chain structure, end group structure, and molecular weight distribution (average molecular weight, polydispersity). Analysis of end group structure is particularly important for the following reasons.
-
The physical properties of polymer materials can change depending on the end groups, even though they are relatively small part of the whole polymer molecules.
-
End group structure might change (or degrade) due to environmental exposures.
-
End group structure can provide insight into the polymerization mechanism.
MALDI is a soft ionization method that allows the observation of polymer molecules as singly charged ions. Using high-resolution MALDI-TOFMS, it is possible to elucidate the elemental compositions of end groups from the accurate masses. On the other hand, pyrolysis GC-TOFMS analyzes the pyrolysis products produced by instantaneous heating of a polymer. Mainly monomers and dimers are observed, but if pyrolysis products containing end groups are observed, structural information on the end groups can be obtained. In this report, we performed structural analysis of the end groups of poly(methyl methacrylate) by using MALDI-TOFMS and pyrolysis GC-TOFMS in a complementary manner.