摘要： Rationale Numerous new tin catalysts were recently developed that enable the synthesis of cyclic polylactides with broad variation of the molecular mass. The abundance of cyclics in MALDI TOF mass spectra is, however, frequently reported to greatly exceed that of linears. Thus the MALDI ionization behavior of various end-capped linear poly(L-lactide)s and one cyclic poly(L-lactide) was investigated and compared. Methods Neat compounds and various blends of cyclic and linear species were prepared and studied under identical conditions with regard to sample preparation and instrumental condition, except for the laser power. For this purpose, two different MALDI TOF mass spectrometers were applied. Results Our results reveal that cyclics indeed show a slightly better ionization in MALDI, although their ionization as neat compound seems to be less effective than that of linear polylactides. The ionization of most linear polylactides investigated does not depend on the end group structure. However, linear polylactides containing 12-bromododecyl end groups reveal an unexpected saturation effect that is not caused by fragmentation of the polymer or the end group, or by electronic saturation of the detector digitizer. Furthermore, polylactides with a 2- bromoethyl end group did not show such a saturation effect. Conclusions An overestimation of cyclic species in MALDI TOF mass spectra of poly(L-lactide)s must be considered, but the commonly assumed peak suppression of linear polymers in mixtures of both architectures can be excluded.