STRUCTURAL CHARACTERIZATION OF MODEL POLYESTER POLYURETHANES USING TIME-OF-FLIGHT SECONDARY ION MASS-SPECTROMETRY

Time-of-flight secondary ion mass spectra (TOF-SIMS) of a polyester and polyurethanes based on polyesters and diisocyanates were obtained from thin films cast from solution on silver substrates. Intact polyester or polyurethane oligomers and large fragments characteristic of the ester and ester-urethane blocks in polyurethanes, both cationized with Ag+ and Na+, were detected in the mass range m/z = 500-3300. The mass of the repeat unit of the polyester in a polyurethane can be determined from the spacing between oligomer or fragment peaks cationized with the same cation. The mass of the urethane can be determined by comparing fragments characteristic of ester and ester-urethane blocks consisting of the same number of repeat units and cationized with the same cation. The combined mass of the terminal groups can be determined from the mass difference between oligomer and fragment ions characteristic of the ester-urethane parts. The masses of unknown alcohol extenders in polyurethanes were determined from m/z values of fragment ions by subtracting the masses of ester and urethane repeat units and cation. The transesterification products of polyester polyurethanes and trifluoroacetic acid were identified from the spectra to be diesters of trifluoroacetic acid and the did in the polyurethane; they consist of an integral number of ester repeat units with or without a urethane and an additional did. Differences and similarities between various polyurethanes can be assessed by comparing their fragmentation patterns. Diols and diisocyanates can be identified by comparing fragments with or without a urethane and transesterification products. © 1990, American Chemical Society. All rights reserved.