One-Pot Synthesis of All-Conjugated Block-Like Bisthiophene–Naphthalenediimide/Fluorene Copolymer

Abstract

A copolymerization of electron-rich and electron-deficient monomers via the chain-growth catalyst-transfer polycondensation route is highly challenging and has never been accomplished thus far, to the best of our knowledge. Herein, we report a simple method to copolymerize two monomers of a significantly different nature: anion-radical naphthalene diimide–dithiophene-based and zinc-organic AB-type fluorenic ones. We found that the copolymerization proceeds rapidly in the presence of Pd catalyst having the bulky and electron-rich tri<i>-tert</i>-butylphosphine ligand. Despite the fact that the two monomers are simultaneously added to the copolymerization (batch polymerization), the polymerization leads to a gradient or even block-like copolymer rather than to a random copolymer or to a mixture of homopolymers, as evident from NMR, GPC, AFM, and fluorescence quenching experiments. The block-like copolymer is formed because the fluorenic monomer polymerizes much faster, yet because the resulting PF2/6 homopolymer is able to initiate polymerization of the second monomer, presumably acting as macroinitiator. Although the investigated copolymerization does not involve a living propagation mechanism and the resulting product is not a well-defined block copolymer, this result is an important step toward a general protocol for preparation of all-conjugated donor–acceptor block copolymers for optoelectronic applications