Structural characterization of aromatic polyester resins by matrix-assisted laser desorption/ionization mass spectrometry

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Eur. J. Mass Spectrom. 7, 15 - 23 (2001)

Structural characterization of aromatic polyester resins by matrix-assisted laser desorption/ionization mass spectrometry

Olli Laine and Pirjo Vainiotalo^*
University of Joensuu, Department of Chemistry, PO Box 111, 80101 Joensuu, Finland. E-mail:
Heidi Österholm
Fortum Oil and Gas, Technology Centre, PO Box 310, 06101 Porvoo, Finland
Hannele Järvinen
Neste Chemicals, Polyester Europe North, PO Box 320, 06101 Porvoo, Finland

ABSTRACT:

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was used to characterize average molecular weights and end-groups of synthetic aromatic polyesters and the same characteristics were also determined for acetylated polyester samples. In addition, the progress of a polyesterification reaction was followed by mass spectrometry by investigating samples taken from the reaction mixture at different reaction times. Average molecular weights were compared with those measured by gel-permeation chromatography (GPC) and the results of quantitative end-group analysis were considered with the acid values of the polyesters. MALDI measurements were carried out using two different matrix compounds, 2,5-dihydroxybenzoic acid (DHB) and 2-(4-hydroxyphenylazo)benzoic acid (HABA). Different matrices and derivatization of the polyester influenced the width of the polymer distribution determined by mass spectrometry and further affected the proportions of differently terminated oligomers, in addition to the average molecular weight. The relative amount of the most abundant oligomer species was increased when the polymer distribution width was increased.

Keywords: average molecular weight, end-group analysis, MALDI, mass spectrometry, polyester, polymer

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