2022 Fiscal Year Research-status Report
Synergistic catalysis for the sustainable synthesis of semiconducting polymers
| Project/Area Number |
22K20547
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| Research Institution | Okinawa Institute of Science and Technology Graduate University |
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Principal Investigator |
高橋 慶子 (ラスカムクリスティーヌ) 沖縄科学技術大学院大学, パイ共役ポリマーユニット, 教授 (70960970)
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| Project Period (FY) |
2022-08-31 – 2024-03-31
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| Keywords | Polymers / Conjugated Polymers / Semiconducting polymers / CH activation / CDC coupling |
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| Outline of Annual Research Achievements |
In recent years, semiconducting polymers have attracted much interest in a wide range of applications in organic electronics, including organic light emitting diodes (OLEDs), organic field-effect transistors (OFETs), organic photovoltaics (OPVs), and more recently, in biological applications. The advances made in performance of these materials can largely be attributed to the synthesis of ever more complex polymers, which can be costly, time-consuming, and environmentally unsustainable. In this proposal, we have investigated the use of cross-dehydrogenative coupling (CDC) polymerizations to improve the efficacy of the synthesis. Key achievements this past year are the following:
1. Expansion of monomer scope that can be used in the CDC polymerization. One new donor monomer (furan) paired with tetrafluorobenzene and one new acceptor (difluorobenzothiadiazole) paired with thiophene have been identified.
2. Development of donor-acceptor (DA monomers) to facilitate the transition towards achieving a living polymerization. In addition to atom economy, minimizing time and energy input in the synthetic process of D-A semiconducting polymers is an essential part of improving the environmental friendliness and scalability of D-A semiconducting polymer production. Based on our prior results that a rate enhancement was observed as the chain extended, DA-type monomers were synthesized hypothesizing that these would lead to more rapid polymerizations. The data show that the DA-type monomer leads to a rate acceleration of 5x compared to the polymerization of a D monomer and an A monomer.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In our original proposal, we had indicated that (i) the exploration of new monomers would take 6 months, (ii) catalyst/ligand exploration would take an additional 6 months, (iii) the DA-type macromonomer design would take the next 6 months, and (iv) achieving controlled chain-growth polymerization would be the final 6 months. While the order of the work has been reversed, with the 3rd aim has been switched with the 2nd aim, our work remains on track based on the original research plan.
Investigation of monomer scope: In addition to the successful monomer combinations that were found, we also identified monomer pairs that did not facilitate the CDC polymerization. Specifically, the following monomer pairs did not result in a polymerization: ethylenedioxythiophene (EDOT) and tetrafluorobenzene, EDOT and difluorobenzothiadiazole, and furan and difluoro benzothiadiazole. These combinations highlight the sensitivity of the polymerization to the exact choice of monomers. For example, difluorobenzothiadiazole does polymerize with thiophene, and it is not immediately obvious why replacing thiophene with furan fails. We are beginning DFT calculations to elucidate what is occurring.
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| Strategy for Future Research Activity |
In the next phase of the research, we will investigate the use of alternative Ag and Pd sources, and ligands. It is known that Ag is primarily responsible for activating the C-H bond for the electron-deficient species while Pd is primarily responsible for activating the C-H bond for the electron-rich species. As such, the ability of each metal to activate different monomers could be fine-tuned through judicious ligand selection as well as counterion selection in the case of Ag. Examples of Ag salts that will be explored include AgOPiv, Ag2CO3, and Ag-adamantane-1-carboxylate. Ligands or Pd precatalysts that will be explored include PPh3, PtBu3, SPhos, PEPPSI-IMes, PEPPSI-IPr, and PEPPSI-IPent.
In the final stages of this award, we will explore the mechanism of the polymerization and how we can facilitate the change-over of a step-growth polymerization to a chain-growth polymerization with our ultimate goal to achieve a living polymerization - the ultimate goal is beyond the scope of the 2-year award. Thus far, we have identified that all polymerization goals used have resulted in a step-growth polymerization, including our work with the DA-type monomer. Judicious catalyst/ligand/monomer selection will be a crucial feature in achieving a chain-growth polymerization.
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Research Products
(5 results)
