CHARACTERIZATION OF POLYESTERS BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY

A series of aliphatic polyesters, characterized by assymetric oligomer distributions, heteroterminated linear chains, and cyclic oligomers, were studied using MALDI. The results from structural characterization of these materials was compared with those acquired using fast atom b ombardment mass spectrometry (FAB-MS), electrospray ionization mass sp ectrometry (ESI-MS), nuclear magnetic resonance (NMR) spectroscopy, an d end group titration. Information on the composition of these polymer s obtained from MALDI, ESI-MS, and end group titration showed reasonab le agreement. However, the MALDI ionization efficiency appeared to be higher for carboxyl-terminated oligomers. MALDI molecular weight deter mination were contrasted with those from GPC and NMR. Reasons for disp arities in the results between the three methods are discussed. The fe asibility of using acidolysis for structural characterization of high molecular weight or insoluble materials was explored. Reaction of the polyesters with trifluoroacetic acid (TFA) produced mono- and bis(trif luoroacetate) esters of the starting material. The products were chara cterized and the progress of the reaction was monitored using MALDI.