High Molar Mass Poly(trimethylene carbonate) by Ph2BiOEt and Ph2BiBr-Initiated Ring-Opening Polymerizations


Trimethylene carbonate, (TMC), was polymerized in bulk with Ph2BiOEt or Ph2BiBr as initiators. The dependence of the molecular weight on the monomer-initiator ratio (M/I) and the MALDI-TOF (MT) mass spectra suggest that these polymerizations obey a coordination-insertion mechanism. Due to “back-biting” cyclic oligomers were also formed. With Ph2BiBr particularly high molecular weights were achieved (number averages, Mns, up to 340 times 103 Da), but the Mns were significantly higher than the M/Is. However, a satisfactory control of Mn was achieved by addition of tetraethylene glycol as coinitiator. In the case of Ph2BiOEt the Mns fell below the M/Is and only a crude control of the Mns was achieved. Both Bi-compounds were more reactive than Sn(II)2-ethylhexanoate (SnOct2) activated with ethanol. This difference was particularly conspicuous at temperatures below 100°C.
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