Nonstoichiometric Migita-Kosugi-Stille Coupling Polycondensation based on Intramolecular Catalyst Transfer System

Abstract

In this paper, a nonstoichiometric Migita-Kosugi-Stille coupling polycondensation based on intramolecular catalyst transfer systems has been reviewed. The achievement of those systems is significant from the viewpoints of (1) acquisition of new knowledge in the synthesis of semiconducting polymer materials, (2) unnecessary strict control in monomer feed ratios generally required for a single-phased solution polycondensation, (3) possible improvement of the monomer reactivity by varying feed ratios, and (4) possibility of controlled chain end groups and extension to the synthesis of all-conjugated block copolymers. In practice, naphthalene-diimide-, phthalimide-, and terephthalate-based π-conjugated polymers have been synthesized under imbalanced stoichiometric conditions, possessing much higher molecular weights than those based on Carothers/Flory’s theory. The results of various model reactions and DFT calculations have revealed that the origin of the intramolecular catalyst transfer phenomenon is related to the existence of carbonyl groups introduced at the ortho-position of dibromo aryl monomers used in excess as well as types of palladium catalysts/precatalysts. In the near future, the proposed nonstoichiometric Migita-Kosugi-Stille coupling polycondensation will be established by extending the adaptable monomers and further optimizing catalysts/precatalysts.