Matrix assisted laser desorption ionization time-of-flight mass spectrometry of synthetic polymers

Characterization of synthetic polymers is demonstrated using matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The spectral distribution of oligomers was used to determine the number average (M_n) and weight average (M_w) molecular weights and polydispersities. Resolution of individual oligomers allowed determination of the repeat unit and terminal group mass of these materials.; Positive ion MALDI-TOF-MS spectra were obtained from a series of polyglycols and poly(dimethyl siloxane) using over 20 liquid matrix systems. These matrices are characterized by simple and rapid sample preparation and exhibited good vacuum stability. Spot-to-spot and point-to-point reproducibility of signal were indicative of the homogeneity of these systems. The best performance was achieved when the UV chromophore 2-cyano-5-phenyl-2,4-pentadienoic acid was employed at or near saturation concentrations.; A series of aliphatic polyesters produced spectra indicating asymmetric distributions and the presence of cyclic oligomers and hetero-terminated linear chains that were identified using MALDI-TOF-MS. The results from structural and molecular weight determinations of these materials was compared with those obtained from other analytical techniques. The feasibility of using acidolysis for structural characterization of high molecular weight or insoluble materials was explored. Products were identified and the progress of the reaction was monitored using MALDI-TOF-MS.; Discreet mass poly(butylene glutarate) (PBG) oligomers of degrees of polymerizations 2, 4, 6, 8, 16, and 32 were synthesized to study reasons for differences in polymer molecular weight averages obtained using MALDI and GPC. The synthesis, purification, and analysis of these materials are discussed. An equi-molar mixture of PBG oligomers having degrees of polymerization 8, 16, 32, and 64 was utilized as a model of polydispersed distributions in the mass range 780–6040 Da. Results indicated that mass dependency of MALDI response was negligible when optimal sample preparation and instrumental parameters were employed for analysis. The application of PBG oligomers as internal standard provided correction of the molecular weight averages from MALDI analysis of polydispersed poly(butylene adipate). Application of PBG oligomers as GPC and mass spectrometric calibration standards was demonstrated.