Fragmentation behavior of poly(methyl methacrylate) during matrix-assisted laser desorption/ionization

Area of Science:

• Polymer Chemistry
• Analytical Chemistry
• Mass Spectrometry

Background:

• Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a key technique for synthetic polymer characterization.
• Polymer decomposition during MALDI-MS can complicate structural analysis.
• Investigating fragmentation behavior is essential for reliable polymer characterization.

Purpose of the Study:

• To investigate the fragmentation behavior of radically polymerized poly(methyl methacrylate) (PMMA) during laser irradiation in MALDI-MS.
• To identify the specific fragmentation pathways and conditions affecting PMMA decomposition.
• To assess the impact of polymer structure on fragmentation susceptibility.

Main Methods:

• Examined two types of PMMA samples with varying structural stability (oligomeric molar mass).
• Utilized high-resolution MALDI spiral time-of-flight MS for precise ion assignment.
• Performed electrospray ionization MS for comparative analysis.

Main Results:

• PMMA chains fragmented during MALDI-MS, even with high laser intensity for stable samples.
• Fragmentation primarily occurred via 1,5-hydrogen rearrangements.
• Less stable structures, like head-to-head linkages in Sample B, decomposed selectively even at low laser intensity.

Conclusions:

• MALDI-MS fragmentation of PMMA under high laser power mirrors MALDI-MS/MS fragmentation.
• Low laser intensity can also induce decomposition of labile PMMA structures.
• Potential fragmentation must be considered for accurate structural characterization of synthetic polymers using MALDI-MS.