Ring-opening oligomerization of propylene carbonate initiated by the bisphenol A/KHCO3 system: A matrix-assisted laser desorption/ionization mass spectrometric study of the oligomers formed

The decarboxylation upon oligomerization of propylene carbonate in the pres ence of the bisphenol A/KHCO3 initiating system was studied by means of mat rix-assisted laser desorption/ionization time-of-flight mass spectrometry ( MALDI-TOF MS). Five different series of peaks appeared in the MALDI-TOF MS spectra of the oligomerization mixture. In addition to the chain-extension reaction with the propylene oxide units, the oligomers of all of the propyl ene oxide units and oligomers containing carbonate end groups condensed. Th e product of the oligomerization reaction was hydrolyzed under alkaline con ditions. It was found that hydrolyzed oligomers do not carry carbonate grou ps. The results of the MS studies agreed well with those obtained by H-1 an d C-13 NMR spectroscopies and size-exclusion chromatography (SEC). On the b asis of the results of the present investigation, a mechanism for the oligo merization is also proposed.