MALDI-TOF mass spectrometry in polymer analytics, 1. Monitoring the polymer-analogous sulfonation reaction of polystyrene

✍ Scribed by Hans Joachim Räder; Jochen Spickermann; Klaus Müllen

• Book ID: 102939206
• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 560 KB
• Volume: 196
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.1995.021961208

✦ Synopsis

Abstract

In the present paper, homologous series of polystyrenes, poly(styrenesulfonic acid)s and their corresponding sodium salts in a mass range between 2000 and 100000 Dalton were used as model systems, to check for the significance of matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI‐TOF MS) in the analysis of synthetic polymers. These three different types of polymers were specially selected, because they are related to each other by polymer‐analogous reactions. The difference in molecular weight between the parent polystyrenes and the poly(styrenesulfonic acid)s or their sodium salts, respectively — prepared from the same sample — provides information on the sulfonation efficiency. It thereby appears that the mass spectrometric monitoring of a polymer analogous reaction proceeds with much greater accuracy than other methods, such as gel permeation chromatography. The measured polymer distributions supply exact values of peak molecular weight (M~p~), number‐average molecular weight (M~n~), weight‐average molecular weight (M~w~) and polydispersity (D = M~w~/M~n~) which turn out to be close to those values calculated for a complete (100%) transformation in the given polymeranalogous reaction. Additional information is available in the mass range below 10000 Dalton, where single chains of the polymers are resolved. Based on the identified polymer ions, the ionization mechanism for poly(styrenesulfonic acid)s and their sodium salts seems to deviate from the mechanism proposed for the ionization of biomolecules. The exact assignment of all signals shows that there is virtually no fragmentation of the polymer ions during measurement. Even the polyionic sodium salt is analyzed together with the counterions.