Kumada Catalyst-Transfer Polycondensation: Mechanism, Opportunities, and Challenges.

Kumada catalyst-transfer polycondensation (KCTP) is a new but rapidly developing method with great potential for the preparation of well-defined conjugated polymers (CPs). The recently discovered chain-growth mechanism is unique among the various transition metal-catalyzed polycondensations, and has thus attracted much attention among researchers. Most progress is found in the areas of mechanism and external initiation via new initiators, but also the number of monomers other than thiophene that can be polymerized is steadily increasing. Accordingly, the variety of CP chain architectures is increasing as well, and a considerable contribution of KCTP toward more efficient materials can be expected in the future. This review critically focuses on very recent progress in the synthesis of CPs and the mechanism of KCTP, and is finally aimed at providing a comprehensive picture of this exciting polymerization method.