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1. Tuning the surface energies in a family of poly-3-alkylthiophenes bearing hydrophilic side-chains synthesized via direct arylation polymerization (DArP)

   https://doi.org/10.1039/D1PY00195G  

   Schmitt, Alexander; Samal, Sanket; Thompson, Barry C. (May 2021, Polymer Chemistry)

   null (Ed.)

   Recent work has identified surface energy as a key figure of merit in predicting the morphology of bulk heterojunction organic solar cells and organic alloy formation in ternary blend organic solar cells. An efficient way of tuning surface energy in conjugated polymers is by introducing functionalised side chains. Here, we present a systematic study on a family of poly(3-hexylthiophene) (P3HT)-based random copolymers bearing five different functionalised side chains (ester, ether, diether, carbamate, nitrile) prepared by direct arylation polymerization (DArP) in terms of their effectiveness in tuning surface energy. This study also exemplifies the superior functional group tolerance in DArP compared to more traditional polymerization procedures. Water droplet contact angle measurements revealed that especially carbamates are highly effective in tuning surface energy, increasing the surface energy from 21.2 mN m −1 with P3HT to 25.5 mN m −1 and 28.6 mN m −1 in 25% and 50% carbamate functionalized copolymers, respectively. Importantly, by introducing a two-carbon-spacer between the conjugated backbone and the functional group, optical and electronic properties of P3HT could be largely maintained in the copolymers as determined by UV/Vis, cyclic voltammetry and space charge limited current hole mobility. 

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2. Approaches for improving the sustainability of conjugated polymer synthesis using direct arylation polymerization (DArP)

   https://doi.org/10.1039/c9py01534e  

   Pankow, Robert M.; Thompson, Barry C. (January 2020, Polymer Chemistry)

   Direct arylation polymerization (DArP) provides a more sustainable alternative to conventional methods for conjugated polymer synthesis, such as Stille–Migita or Suzuki–Miyura polymerizations. DArP proceeds through a C–H activation pathway, allowing for a reduction in the synthetic steps needed to access the monomer, since the installation of a transmetallating reagent, such as an organostannane or organoboron, is not required. However, compared to small-molecule synthesis, the prevalent conditions employed for DArP still require hazardous or unsustainably sourced reaction components, such as the solvent and transition-metal catalyst. This mini-review highlights recent work on the implementation of sustainable solvents, transition metal catalysts, and overall polymerization methods for DArP. The extension of small-molecule direct arylation conditions towards polymer synthesis is also discussed, along with the associated challenges, mechanistic considerations, and outlook for future work. 

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3. The Direct Arylation Polymerization (DArP) of Well‐Defined Alternating Copolymers Based On 5,6‐Dicyano[2,1,3]benzothiadiazole (DCBT)

   https://doi.org/10.1002/ajoc.201800232  

   Shi, Qinqin; Tatum, Wesley; Zhang, Junxiang; Scott, Colleen; Luscombe, Christine_K; Marder, Seth_R; Blakey, Simon_B (June 2018, Asian Journal of Organic Chemistry)

   Abstract Alternating donor–acceptor copolymers are important materials with readily tunable optical and electronic properties. Direct arylation polymerization (DArP) is emerging as an attractive synthetic methodology for the synthesis of these polymers, avoiding the use of prefunctionalized building blocks. However, challenges remain in achieving well‐defined structure, high molecular weight, and impurity‐free polymers. Herein, a study to synthesize three well‐defined donor–acceptor copolymers through DArP is presented. Comparison of¹H NMR and¹³C NMR, as well as optical and electrochemical properties analysis for the polymers and corresponding oligomers provides evidence for the regioregular structure of the polymers. On the basis of the chemical structure of poly(IIDCBT) and the solution electrochemical studies we surmised poly(IIDCBT) could potentially be an electron transport material for organic field‐effect transistors (OFETs), and we determined an electron mobility of 1.2×10⁻³ cm² V⁻¹ s⁻¹for this material. 

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4. Synthesis of conjugated polymers using aryl-bromides via Cu-catalyzed direct arylation polymerization (Cu-DArP)

   https://doi.org/10.1039/c9py01478k  

   Ye, Liwei; Pankow, Robert M.; Schmitt, Alexander; Thompson, Barry C. (December 2019, Polymer Chemistry)

   Initial reports on the novel Cu-catalyzed direct arylation polymerization (Cu-DArP) stated that it required the use of aryl iodides. Herein, we report the first Cu-DArP methodology using more accessible and practical aryl-bromides with catalytic Cu, leading to a range of conjugated polymers with good molecular weights (up to 17.3 kDa) and an undetectable level of defects. 

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5. Improving the efficiency and sustainability of catalysts for direct arylation polymerization (DArP)

   https://doi.org/10.1002/pol.20210524  

   Ye, Liwei; Thompson, Barry C. (September 2021, Journal of Polymer Science)

   Abstract In the past decade, direct arylation polymerization (DArP) has rapidly developed as a sustainable synthetic protocol for cost‐effective, atom‐economical preparation of conjugated polymers. By circumventing monomer functionalization with toxic transmetallating reagents such as organostannane and organoboron required for Stille‐Migita and Suzuki‐Miyaura polymerization methods, DArP proceeds through a metal‐catalyzed CH activation pathway for the preparation of high‐performance conjugated polymer materials. This review evaluates the development of several classes of efficient catalysts/catalytic systems from small‐molecule studies to polymerizations, including the mechanisms involved in these transformations and how they inspire catalyst and monomer design for defect‐free conjugated polymer synthesis. Recent advances in developing more sustainable first‐row transition metal catalysts for DArP are also highlighted, and the fundamental understanding of these efficient and sustainable catalysts should motivate the pursuit for the next generation of catalytic design to enable more effective and environmentally friendly conjugated polymer synthesis. 

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