MALDI-TOF mass spectrometry of tin-initiated macrocyclic polylactones in comparison to classical mass-spectroscopic methods

摘要

2,2-Dibutyl-2-stanna-1,3-dioxepane (1) was used as cyclic initiator for the (ring expansion) polymerization of L-lactide, #epsilon#-caprolactone, #beta#-D,L-butyrolactone and 1,4-dioxane-2-one. The polymerizations were conducted in bulk at 80 and 120 deg C with monomer/initiator mole ratios of 6, 10, and 20. When the resulting macrocyclic oligolactones (DP-6) were subjected to mass spectroscopy total thermal degradation via transesterification took place and the original molecule peak was not detectable. In the case of fast atom bombardment (FAB) and matrix-assisted laser desorption ionization/time of flight (MALDI-TOF) measurements the alcohols or phenols used as matrix materials cleave the Sn--O bonds of the macrocycles and the MALDI-TOF mass spectra showed the molecule peaks of OH-terminated telechelic polylactones. Stoichiometric insertion of #gamma#-thiobutyrolactone into the Sn--O bonds yielded stabilized macrocyclic polylactones containing the less reactive Sn--S bonds, which allowed the recording of FAB and MALDI-TOF mass spectra showing the molecule peaks of intact tin-containing cyclic oligo- and polylactones.