Green-Solvent-Processed Amide-Functionalized Conjugated Polymers Prepared via Direct Arylation Polymerization (DArP)

Abstract

Organic electroactive materials that can be processed using simple alcohols, such as ethanol and 1-butanol, are highly desired, since these solvents can be sourced from biomass and present lower hazards for human and environmental health. Herein, we report the first class of poly­(3-alkylamidethiophenes) (P3AAT) synthesized via the sustainable method of direct arylation polymerization (DArP) that can be processed using green, sustainable solvents. The unprecedented synthesis of P3AAT reveals the superiority of DArP, as P3AAT can be readily prepared in only three simple steps with an M n of up to 15.4 kDa and yields of up to 90% exclusively with this methodology. The tertiary amide, poly­(N-hexyl-N-methylthiophene-3-carboxamide-2,5-diyl) (P1), has excellent solubility in the green solvents ethanol, 1-butanol, and anisole. Processing of P1 in 1-butanol is shown to provide comparable space-charge-limited current (SCLC) hole mobility versus dichlorobenzene and commensurate photophysical properties. Also, the secondary amide, poly­(N-(2-ethylhexyl)­thiophene-3-carboxamide-2,5-diyl) (P2), was successfully synthesized, demonstrating excellent functional group tolerance for DArP, while showing hydrogen-bonding features and similar SCLC hole mobility as P1. This study provides a facile synthetic strategy for a novel structural motif that can be processed in sustainable solvents without a compromise in performance, which can easily be extended to other valuable areas of organic electronics and bioelectronics.

Optimizing the self‐assembly of conjugated polymers and small molecules through structurally programmed non‐covalent control

“…Hydrogen bonding sidechains can improve interchain packing, solid-state microstructure, and charge transport of both n-type and p-type conjugated polymers, [109][110][111] with amide groups especially useful given the strength of hydrogen bonding between them. [112][113][114][115] An exemplar of this design came in 2018 from Ocheje et al 116 Their family of diketopyrrolopyrrole polymers (Figure 7) possessed amide-containing aliphatic chains that participated in interchain hydrogen bonding throughout the polymer network. A small percentage of amide containing side-chains (5 mole %) increased charge mobility by 32% in annealed devices, which the authors attributed to stronger interchain interactions throughout the polymer network.…”

“…However, designer side‐chains possessing hydrogen bonding functional groups, such as amides and ureas, can accomplish more than simply imparting solubility. Hydrogen bonding side‐chains can improve interchain packing, solid‐state microstructure, and charge transport of both n‐type and p‐type conjugated polymers, 109–111 with amide groups especially useful given the strength of hydrogen bonding between them 112–115 . An exemplar of this design came in 2018 from Ocheje et al 116 Their family of diketopyrrolopyrrole polymers (Figure 7) possessed amide‐containing aliphatic chains that participated in interchain hydrogen bonding throughout the polymer network.…”

Optimization of the Reaction Conditions for Direct Arylation Polymerizations in a Sustainable Solvent

“…[ 17 ] Notwithstanding CPME is currently synthesized by petrochemical derivatives with a high atom economy, its production could also involve natural substrates, such as furfural or adipic acid. [ 18 ] To the best of our knowledge, however, few are the cases concerning the use of CPME [ 19–22 ] as well as of other green solvents (especially, 2‐MeTHF) [ 23–25 ] as a sustainable medium for the synthesis of conjugated polymers via DArP.…”

Synthesis of Conjugated Polymers via Transition Metal Catalysed C−H Bond Activation

“…Thompson's group reported the preparation of an amide functionalised thiophene polymer (Scheme 5a). [36] Preparation of this polymer by conventional Stille coupling or Grignard metathesis was non-trivial due to issues with monomer preparation or functional group compatibility during polymerisation. The electrochemical properties of these new polymers were also measured.…”

“…(a) DArP preparation of a novel amide functionalised thiophene polymer and its hole-transport properties. [36] (b) Unsuccessful DArP of adenine functionalised thiophene polymer. [37] (c) Successful DArP to form A3c, which could subsequently be de-protected by TFA.…”