MATRIX-ASSISTED LASER-DESORPTION IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY OF SYNTHETIC POLYESTERS

We report the analysis of aliphatic and aromatic polyesters by matrix- assisted laser desorption-ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) using 2,5-dihydroxybenzoic acid and t-3-indoleacrylic a cid as matrices. Broad asymmetrical distributions of linear oligomer r elated peaks (protonated and cationised molecules) were observed with both matrices. Peaks corresponding to cyclic oligomers were observed f or the aliphatic polyester. The oligomer molecular weight distribution derived from the MALDI spectra exhibits a certain variability with bo th laser fluence and matrix material. This effect probably originates from different solubilities of the various oligomers. In addition, for those polycondensates which are characterised by a very broad distrib ution with a tail in the high mass range, a discrimination against the higher mass oligomers is likely to exist; the agreement between the a verage molecular weights determined by MALDI and size exclusion chroma tography is not as good as for poly(ethylene glycol) or poly(methyl me thacrylate).