Differentiation of Linear and Cyclic Polymer Architectures by MALDI Tandem Mass Spectrometry (MALDI-MS2)

• Published in: Journal of the American Society for Mass Spectrometry Vol. 24; no. 1; pp. 74 - 82
• Main Authors: Yol, Aleer M., Dabney, David E., Wang, Shih-Fan, Laurent, Boyd A., Foster, Mark D., Quirk, Roderic P., Grayson, Scott M., Wesdemiotis, Chrys
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 01.01.2013; Springer Nature B.V
• Subjects: AC generators; Analytical Chemistry; Bioinformatics; Biotechnology; Butadienes - chemistry; Chemistry; Chemistry and Materials Science; Depolymerization; Desorption; Disproportionation; Elastomers - chemistry; Fragmentation; Fragments; Inspection; Ionization; Ions; Lasers; Mass spectrometry; Mathematical analysis; Matrix methods; Models, Molecular; Organic Chemistry; Polybutadiene; Polystyrenes - chemistry; Proteomics; Radicals; Research Article; Scientific imaging; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; Spectroscopy; Tandem Mass Spectrometry - methods; Cyclic versus linear structure; Tandem mass spectrometry; Synthetic polymers; MALDI; Macromolecular architecture
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1007/s13361-012-0497-5

[M + Ag] + ions from cyclic and linear polystyrenes and polybutadienes, formed by matrix-assisted laser desorption ionization (MALDI), give rise to significantly different fragmentation patterns in tandem mass spectrometry (MS 2 ) experiments. In both cases, fragmentation starts with homolytic cleavage at the weakest bond, usually a C–C bond, to generate two radicals. From linear structures, the separated radicals depolymerize extensively by monomer losses and backbiting rearrangements, leading to low-mass radical ions and much less abundant medium- and high-mass closed-shell fragments that contain one of the original end groups, along with internal fragments. With cyclic structures, depolymerization is less efficient, as it can readily be terminated by intramolecular H-atom transfer between the still interconnected radical sites (disproportionation). These differences in fragmentation reactivity result in substantially different fragment ion distributions in the MS 2 spectra. Simple inspection of the relative intensities of low- versus high-mass fragments permits conclusive determination of the macromolecular architecture, while full spectral interpretation reveals the individual end groups of linear polymers or the identity of the linker used to form the cyclic polymer. Figure Macrocyclic and linear polystyrene and polydiene architectures are conclusively distinguished by the MS 2 fragmentation patterns of Ag + -cationized oligomers.