Oligomers molecular weights from MALDI

Matrix-assisted laser desorption ionization MS is well represented in this area [56, 85-94]. Cox et al. [88] used MALDI-MS to characterize low molecular weight polyolefin copolymers of isobutylene and paramethylstyrene and to extract composition information from spectra. Comparison of experimental oligomer distributions to a Bemoullian statistical model revealed severe overrepresentation of oligomers with higher relative amounts of paramethylstyrene. However, good agreement between the model and experimental data was obtained by the introduction of an ionization efficiency term in the model used. The differences between average composition determined by MALDI and NMR were discussed. 

A series of aliphatic polyesters, characterised by asymmetric oligomer distributions, heteroterminated linear chains, and cyclic oligomers, were studied using MALDI. Structural characterisation results were compared with those from fast atom bombardment mass spectrometry, electrospray ionisation mass spectrometry, NMR and end-group titration. MALDI molecular weight determination was contrasted with those from GPC and NMR. 23 refs. 

---