Tlme-of-tllght secondary Ion mass spectra of a series of polyurethanes based on three diols and four dllsocyanates were obtained from thin polyurethane films cast from solution on silver substrates. Intact oligomer Ions and large polyurethane fragments consisting of an Integral number of repeat units, both catlonlzed with Ag+ and Na+, were detected In the mass range m/z = 500-3200. The mass of the repeat unit of a polyurethane can be determined from m/z values of oligomer or fragment Ions or from the spacing between consecutive peaks generated from fragments or oligomers catlonlzed with the same cation. The combined mass of the terminal groups can be determined from the mass difference between oligomer and fragment peaks. Identities of the dlol and diisocyanate In a polyurethane can be obtained by comparing different fragmentation patterns In the spectrum; differences and similarities between polyurethanes can thus be assessed. Transesterification products of polyurethanes and trlfluoroacetlc acid were Identified from secondary Ion mass spectra to be dlesters consisting of an Integral number of polyurethane repeat units and an additional dlol.
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.
Tlme-d-fllght secondary kn mass spectra were obtained from thin fllms of perfluorinated poly-and copolyethers up to m / z = 6500. The fragmentation for the perfluoropolyethers under Ar' bombardmcMt is ConsMent with the kn stablUtles and the structure of their repeating units. The elucidation of the fregmentatkn patterns for random copdymers Is complkated, because Ions having different structures can correspond to a given peak. The fragmentation patterns are unique and reproducible for each kind of poiyether and copoiyether, independent of sample preparation and substrate. Carbonium fragment ions dominate the positive-ion spectra, and alkoxy lons dominate the negatlve-ion spectra; cationired ollgomers were detected. Small structural differences in the backbone or terminal groups of otherwise identical polymers were detected in the spectra as differences in the fragmentation patterns of in the relative peak intendties or shms in the m / z values of the ollgomer peaks. The number-average molecular weights determined from the oligomer distributions of perfluoropolyethers observed in the spectra are in good agreement with those measured by nuclear magnetic resonance and gas chromatography.
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