One-Pot Synthesis of Fully Conjugated Amphiphilic Block Copolymers Using Asymmetrically Functionalized Push–Pull Monomers

Abstract

Developing a fully conjugated block copolymer with a specific molecular weight and block ratio is crucial for understanding the impact of the bulk heterojunction morphology on device performance in organic photovoltaic devices. Herein, we have revealed a strategy to synthesize fully conjugated amphiphilic diblock copolymers in one pot by combining Suzuki and Stille pseudoliving polymerizations. Our strategy was to synthesize asymmetrically functionalized push–pull monomers as precursors for the synthesis of the donor polymer poly[4,8-bis(5-(2-ethylhexyl)-4-hexylthiophene-2-yl)-benzo[1,2-b:4,5b′]dithiophenebenzo [c][1,2,5]thiadiazole] p(BDT-BT) and the acceptor polymer poly[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene) p(NDI-TT). The acceptor monomer (M1) was synthesized with tributyltin and triflate functionalities, whereas the donor monomer (M2) was prepared with MIDA boronate and bromide groups. These heterobifunctional acceptor and donor monomers were suitable for Stille and Suzuki polymerizations, respectively. Initially, TfOPh-p(NDI-TT) was synthesized by pseudoliving Stille polymerization with a single triflate (OTf) end group and specific molecular weight. Subsequently, TfOPh-p(NDI-TT) was used as a macroinitiator to grow an amphiphilic diblock copolymer (BCP1) via a grafting-into approach, where the donor polymer block was grown using pseudoliving Suzuki polymerization. Lastly, one-pot synthesis of the amphiphilic diblock copolymer (BCP2) was established using optimized conditions developed for stepwise block copolymer synthesis.