Direct Arylation Polymerization of Degradable Imine-Based Conjugated Polymers

Abstract

The development and optimization of reliable polymerization methods are needed for the synthesis of degradable imine-based conjugated polymers, which are attractive materials for transient electronics. Direct arylation polymerization (DArP) has emerged as a sustainable and atom-economical synthetic method for the preparation of well-defined conjugated polymers. Compared to polymerization methods such as imine polycondensation or Stille cross-coupling polymerization, which require monomer functionalization, direct arylation proceeds via C–H activation and thereby reduces synthetic complexities and toxic byproducts. Here, we report the first use of DArP for the synthesis of an imine-based indacenodithiophene (IDT) copolymer, p­(IDT–TIT). Polymers prepared via DArP can result in branched or cross-linked polymer chains due to the reactivity of C–H bonds in the monomers. In this report, we demonstrate a systematic study focusing on the reaction conditions needed to prepare p­(IDT–TIT) via DArP with tetramethylethylenediamine as a coligand. The degradable polymer is characterized via nuclear magnetic resonance spectroscopy, high-temperature gel permeation chromatography, and ultraviolet–visible–near-infrared spectroscopy. With the simplicity of monomer preparation and reaction conditions, we anticipate that this efficient synthetic protocol will lead to higher synthetic adoption in the research community to aid the exploration of high-performance imine-based degradable materials.

Degradable π-Conjugated Polymers

“…Interestingly, the authors suggest that the relatively high free energy of activation for the monomers, coupled with the lower temperature and sterically bulky reagents used in the β-branching-suppressing conditions, may be responsible for slowing the polymerization enough for debromination to outcompete and hinder the polymerization of the β-branching-suppressing conditions. 77 More recently, Tran and co-workers 78 have recently demonstrated the first example of a successful optimization of DArP for the synthesis of a degradable imine-based conjugated polymer. They demonstrated a systematic study that focused on optimization DArP conditions with the use of tetramethylethylenediamine as a coligand to synthesize a new polymer, p(IDT-TIT), composed of indacenothiophene (IDT) and thiophene-iminethiophene (TIT) units (Figure 4i).…”

“…(i) Left: Direct arylation polymerization of a degradable indacenodithiophene- co -thiophene-imine-thiophene poly­(azomethine). Right: Photos of the polymerization between indacenodithiophene and thiophene-imine-thiophene at 0 and 22 h. Images and synthetic schemes adapted with permission from refs , , , and. Copyright 2021 American Chemical Society, 2021 American Chemical Society, 2022 Royal Society of Chemistry, and 2023 American Chemical Society.…”