Characterization of synthetic polymers using matrix-assisted laser desorption/ionization - Time of flight mass spectrometry

Matrix-assisted laser desorption/ionization-time of flight mass spectrometry was used for a detailed characterization of three synthetic polymers. It has been demonstrated that the necessary components of the matrix required for effective desorption of intact oligomer ions depend on the properties of the synthetic polymer. Molecular weight averages were obtained for polystyrene and poly(ethylene glycol) samples by calculating the centroid of the distribution. Polyesters, synthesized from enzymatic polytransesterification of adipic acid esters with 1,4-butanediol, were characterized in detail to obtain significant structural information. Intact oligomer ions, cationized with Nai were detected in the mass range 200-9000. The polyester species detected were terminated at both ends either with OH groups or by a COOH group and an OH group. The presence of these species was confirmed by quantifying the isotopic abundances of these cations and verifying them with theoretical predictions. The presence of -COOH termination was not detected using H-1-NMR, even at low polymer molecular weights. The repeat unit of the polyester was confirmed from the spacing between consecutive peaks with the same end groups. The presence of acid-terminated species was also confirmed by direct titration of the polyester.