Bellan Ekaterina V, Thevenin Lucas, Gayet Florence, Fliedel Christophe, Poli Rinaldo
CNRS, LCC (Laboratoire de Chimie de Coordination), Université de Toulouse, INPT, UPS, 205 route de Narbonne, BP 44099, 31077 Toulouse Cedex 4, France.
Institut Universitaire de France, 1, rue Descartes, 75231 Paris Cedex 05, France.
ACS Macro Lett. 2017 Sep 19;6(9):959-962. doi: 10.1021/acsmacrolett.7b00551. Epub 2017 Aug 17.
The vinyl acetate (VAc) radical polymerization initiated by V-70 at 30 °C in the presence of [Co(OPN)] (OPN = deprotonated 9-oxyphenalenone), , 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 [Co(OPN)(py)], , shows a marginally lower polymerization rate and an increased CCT activity relative to , 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 H 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 [Co(OPN)(py)] relative to and . The presence of py association/dissociation equilibria relating these three complexes was confirmed by a H NMR investigation.
在30°C下，以V-70引发、[Co(OPN)]（OPN = 去质子化的9-氧化菲）存在下的醋酸乙烯酯（VAc）自由基聚合反应，无论采用可逆终止还是退化转移条件，得到的聚醋酸乙烯酯（PVAc）分子量均低于有机金属介导的自由基聚合（OMRP）预期值。这是VAc聚合反应中催化链转移（CCT）的首个明确证据。双吡啶加合物[Co(OPN)(py)]的聚合速率略低，相对于[Co(OPN)]，其CCT活性增加，而加入过量吡啶后，活性降低，对聚合速率的影响较小。然而，将温度升至80°C（以偶氮二异丁腈为引发剂），即使存在大量过量吡啶，也会得到低分子量聚合物。通过链端的核磁共振氢谱（¹H NMR）表征和回收聚合物的基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）分析证实了CCT。这些总体趋势与五配位配合物[Co(OPN)(py)]相对于[Co(OPN)]和[Co(OPN)(py)₂]具有更高的CCT活性一致。通过¹H NMR研究证实了这三种配合物之间存在吡啶缔合/解离平衡。
