Ak. Chaudhary et al., CHARACTERIZATION OF SYNTHETIC-POLYMERS USING MATRIX-ASSISTED LASER DESORPTION IONIZATION - TIME-OF-FLIGHT MASS-SPECTROMETRY/, Macromolecules, 29(6), 1996, pp. 2213-2221
Matrix-assisted laser desorption/ionization-time of flight mass spectr
ometry was used for a detailed characterization of three synthetic pol
ymers. It has been demonstrated that the necessary components of the m
atrix 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 ca
lculating the centroid of the distribution. Polyesters, synthesized fr
om enzymatic polytransesterification of adipic acid esters with 1,4-bu
tanediol, were characterized in detail to obtain significant structura
l information. Intact oligomer ions, cationized with Nai were detected
in the mass range 200-9000. The polyester species detected were termi
nated 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 theoretic
al predictions. The presence of -COOH termination was not detected usi
ng 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.