Menü

Overview

A special attention is paid to detailed understanding of polymerization mechanism of Ni- catalyst-transfer polycondensation as this allows extending the scope of this emerging polymerization technique.

It is now generally accepted that Kumada catalyst-transfer polycondensation KCTP occurs via iterative TM, reductive elimination (RE) and oxidative addition (OA) steps, whereby nickel catalyst is not released from the chain forming a pi-complex with polymer chain.

Figure 1. Catalytic cycle of chain-growth KCTP. OA: oxidative addition, RE, reductive elimination, TM, transmetalation.

We found an intriguing catalyst " ring - walking " process. Particularly, we demonstrated that nickel catalyst can "walk" along the polymerized chain over long distances (tens of monomer repeat units) until it reaches the opposite chain end. In this case, if there is an appropriate C-Br bond, it can initiate polymerization from the opposite chain end.

Figure 2. Unidirectional versus random catalyst ring walking in the KCTP using a bifunctional initiator. Unidirectional polymerization leads to bromophenyl-terminated P3HT while random ring walking leads to P3HT with an internal phenyl group.

References

  • Senkovsky, V.; Tkachov, R.; Beryozkina, T.; Komber, H.; Oertel, U.; Horecha, M.; Bocharova, V.; Stamm, M.; Gevorgyan, S. A.; Krebs, F.C.; Kiriy, A
    Hairy poly(3-hexylthiophene) particles prepared via surface-initiated kumada catalyst-transfer polycondensation. Journal of the American Chemical Society (2009) 16445-16453. more

  • Senkovsky, V.; Khanduyeva, N.; Komber, H.; Oertel, U.; Stamm, M.; Kuckling, D.; Kiriy, A.
    Conductive polymer brushes of regioregular head-to-tail poly(3-alkylthiophenes) via catalyst-transfer surface-initiated polycondensation. Journal of the American Chemical Society 129 (2007) 6626-6632. more

  • Tkachov, R.; Senkovskyy, V.; Beryozkina, T.; Boyko, K.; Bakulev, V.; Lederer, A.; Sahre, K.; Voit, B.; Kiriy, A. Palladium-Catalyzed Chain-Growth Polycondensation of AB-type Monomers: High Catalyst Turnover and Polymerization Rates. Angew. Chem. Int. Ed. (2014), 53, 2402. more