Analysis of polystyrene end group structure by thermal desorption/pyrolysis (TDP) DART-TOFMS
MSTips No.318
Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) are powerful tools in polymer analysis. Py-GC-MS is a method in which a polymer sample is instantaneously heated, and GC-MS analyzes the volatile components generated by thermal decomposition. Although it can be applied to polymers in various states and obtain chemical information, it is not easy to analyze the end group structure. Because the polymers decompose to the monomers and small oligomers, only average information about the sample can be obtained. MALDI-MS can ionize polymers softly, and by selecting an appropriate matrix, it can ionize polymers with a molecular weight of several 100 Da to several 100 kDa. Combining a high-resolution time-of-flight mass spectrometer, a mix of the same polymers with different end groups, a mix of polymers, or a copolymer can be mass-resolved. However, it can be obtained as long as its average molecular weight is up to 10 kDa. Furthermore, the elemental composition estimation of end groups using accurate mass is limited to several kDa.
While there are pros and cons to polymer analysis by Py-GC-MS and MALDI-MS, end group analysis of polymers by thermal desorption/pyrolysis (TDP) -DART-MS has been proposed [1]. This method generates volatile components by gradually heating a polymer sample with the thermal desorption/pyrolysis device and analyzing them with DART-MS. Unlike the rapid heating in Py-GC-MS, gradual heating generates larger oligomers, and DART-MS can detect them. Some of the generated oligomer components include end group structures, which can be a help in the structure analysis of polymers. In this report, we verify that the end group analysis of polystyrene by TDP-DART-MS examined in Reference [1] is possible by the TDP device ionRocket (BioChromato) and AccuTOF™ LC-plus 4G.