mz7b00551_si_001.pdf (1.95 MB)
Catalyzed Chain Transfer in Vinyl Acetate Polymerization Mediated by 9‑Oxyphenalenone Cobalt(II) Complexes
journal contribution
posted on 2017-08-16, 21:31 authored by Ekaterina
V. Bellan, Lucas Thevenin, Florence Gayet, Christophe Fliedel, Rinaldo PoliThe
vinyl acetate (VAc) radical polymerization initiated by V-70
at 30 °C in the presence of [CoII(OPN)2] (OPN = deprotonated 9-oxyphenalenone), 1, leads to
PVAc of lower molecular weight (MW) than expected for organometallic-mediated
radical polymerization (OMRP), whether reversible termination or degenerate
transfer conditions are used. This represents the first clear evidence
of catalyzed chain transfer (CCT) in VAc polymerization. The bis-pyridine
adduct [CoII(OPN)2(py)2], 2, shows a marginally lower polymerization rate and an increased CCT
activity relative to 1, whereas the activity decreases
with marginal effect on the polymerization rate upon addition of excess
py. However, raising the temperature to 80 °C (with AIBN as initiator)
led to a low MW polymer even in the presence of a large py excess.
The CCT was confirmed by 1H NMR characterization of the
chain ends and by a MALDI-TOF MS analysis of the recovered polymer.
The collective trends are consistent with greater CCT activity for
the 5-coordinate complex [CoII(OPN)2(py)] relative
to 1 and 2. The presence of py association/dissociation
equilibria relating these three complexes was confirmed by a 1H NMR investigation.