MALDI-TOF/TOF CID Study of Poly(1,4-dihydroxybenzene terephthalate) Fragmentation Reactions

MALDI-TOF/TOF collision-induced dissociation (CID) experiments were conducted on model aromatic polyester oligomers. CID fragmentation studies identified initial fracture of the ester bond and subsequent CO loss as a major pathway, consistent with the general fragmentation mechanism used to explain the origin of poly(p-phenylenediamine terephthalamide) (PPD-T) fragment ions. Specifically, both charge-remote and charge-site fragmentation were observed. Different parent-ion species were observed, the major ones being carboxyl-hydroxyl, di-carboxyl, di-hydroxyl, and phenyl-carboxyl terminated. One species observed was hydroxyl-diethylamine terminated caused by reaction of carboxyl groups with triethylamine added to the synthesis reaction mixture. Fragment ions reflected the end groups of the parent oligomers. Some MALDI fragment-ion spectra were obtained for species showing exchange between Li and H at the carboxyl end group. Bond energy calculations provide further insight into suggested fragmentation mechanisms.