Conjugated Polymers from Direct Arylation Polycondensation of 3,4‐Difluorothiophene‐Substituted Aryls: Synthesis and Properties

• Published in: Macromolecular rapid communications. 2023-12, Vol.44 (23), p.e2300393-n/a
• Main Authors: Sui, Ying, Zhang, Xuwen, Xu, Chenhui, Shi, Yibo, Deng, Yunfeng, Han, Yang, Geng, Yanhou
• Format: Article
• Language: English
• Subjects: Benzene; Chemical synthesis; conjugated polymers; Density functional theory; direct arylation polycondensation; Electron mobility; Energy levels; Female; Humans; Ketones; Molecular orbitals; Monomers; organic thin‐film transistors; Polyethyleneimine; polymer semiconductors; Polymers; Polymers - chemistry; Pregnancy; Pyrroles - chemistry; Semiconductor devices; Substitutes; Thin film transistors; Thiophenes - chemistry; Transport properties
• ISSN: 1022-1336; 1521-3927
• DOI: 10.1002/marc.202300393

3,4‐Difluorothiophene‐substituted aryls, i.e., 1,4‐bis(3,4‐difluorothiophen‐2‐yl)‐benzene (Ph‐2FTh), 1,4‐bis(3,4‐difluorothiophen‐2‐yl)‐2,5‐difluorobenzene (2FPh‐2FTh), and 4,7‐bis(3,4‐difluorothiophen‐2‐yl)‐2,1,3‐benzothiadiazole (BTz‐2FTh), are synthesized as C─H monomers for the synthesis of conjugated polymers (CPs) via direct arylation polycondensation (DArP) with diketopyrrolopyrrole (DPP) and isoindigo (IID) derivatives as C─Br monomers. The Gibbs free energies of activation for direct arylation (ΔG298 K, kcal mol−1) for α─C─H bonds of thiophene moieties as calculated by density functional theory (DFT) are 14.3, 16.5, and 16.4 kcal mol−1 for Ph‐2FTh, 2FPh‐2FTh and BTz‐2FTh, respectively, meaning that inserting an electron‐deficient unit in 3,3′,4,4′‐tetrafluoro‐2,2′‐bithiophene (4FBT, ΔG298K: 14.6 kcal mol−1) may cause a reactivity decrease of the C─H monomers. Photophysical and semiconducting properties of the resulting six CPs (i.e., DPP‐Ph, DPP‐2FPh, DPP‐BTz, 2FIID‐Ph, 2FIID‐2FPh, and 2FIID‐BTz) are characterized in detail. DPP‐based CPs show ambipolar transport properties while IID‐based ones exhibited n‐type behavior owing to the deeper frontier molecular orbital energy levels of IID‐based CPs. With source/drain electrodes modified with polyethylenimine ethoxylated, n‐channel organic thin‐film transistors with maximum electron mobility of 0.40, 0.54, 0.29, 0.05, 0.16, and 0.01 cm2 V−1 s−1 for DPP‐Ph, DPP‐2FPh, DPP‐BTz, 2FIID‐Ph, 2FIID‐2FPh, and 2FIID‐BTz, respectively, are fabricated. DPP‐2FPh exhibits the best device performance due to the good film morphology and the highest intermolecular packing order. Three C─H monomers Ph‐2FTh, 2FPh‐2FTh, and BTz‐2FTh with 3,4‐difluorothiophene as terminal units and phenyl, 2,5‐difluorophenyl and benzothiadiazole as central units are synthesized for direct arylation polycondensation to diketopyrrolopyrrole‐ and isoindigo‐based high‐mobility conjugated polymers. n‐Channel organic thin‐film transistors with electron mobility up to 0.54 cm2 V−1 s−1 are fabricated based on the resulting polymers.