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Abstract Mechanically deformable polymeric semiconductors are a key material for fabricating flexible organic thin‐film transistors (FOTFTs)—the building block of electronic circuits and wearable electronic devices. However, for many π‐conjugated polymers achieving mechanical deformability and efficient charge transport remains challenging. Here the effects of polymer backbone bending stiffness and film microstructure on mechanical flexibility and charge transport are investigated via experimental and computational methods for a series of electron‐transporting naphthalene diimide (NDI) polymers having differing extents of π‐conjugation. The results show that replacing increasing amounts of the π‐conjugated comonomer dithienylvinylene (TVT) with the π‐nonconjugated comonomer dithienylethane (TET) in the backbone of the fully π‐conjugated polymeric semiconductor, PNDI‐TVT100(yielding polymeric series PNDI‐TVTx, 100 ≥x≥ 0), lowers backbone rigidity, degree of texturing, and π–π stacking interactions between NDI moieties. Importantly, this comonomer substitution increases the mechanical robustness of PNDI‐TVTxwhile retaining efficient charge transport. Thus, reducing the TVT content of PNDI‐TVTxsuppresses film crack formation and dramatically stabilizes the field‐effect electron mobility upon bending (e.g., 2 mm over 2000 bending cycles). This work provides a route to tune π–π stacking in π‐conjugated polymers while simultaneously promoting mechanical flexibility and retaining good carrier mobility in FOTFTs.
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Achieving Closed‐Loop Recycling of a Semi‐Conjugated Polymer Through the Incorporation of Ester Linkers Along the Backbone
Abstract Design strategies to achieve degradation and ideally closed‐loop recycling of organic semiconductors have attracted great interest in order to minimize the electronic waste (E‐waste). In this work, three ester‐incorporated monomers were synthesized by the names of Thiophene‐Ester‐Ethylene‐Thiophene (TEET), Thiophene‐Ester‐Methylene‐Thiophene (TEMT), and Thiophene‐Ester‐Thiophene (TET), which were co‐polymerized via Stille polycondensation with a benzodithiophene (BnDT) π‐conjugated unit to yield a series of ester‐incorporated polymers: PBnDT‐TEET, PBnDT‐TEMT, and PBnDT‐TET. While the ester‐only linker can maintain some extended conjugation in PBnDT‐TET, the other two ester linkers having conjugation breaking units result in isolated conjugated segments in PBnDT‐TEET and PBnDT‐TEMT, evidenced by UV‐Vis and CV results. This yields an improved photovoltaic performance of PBnDT‐TET compared to PBnDT‐TEET. While all three polymers can depolymerize under methanolysis, the alternating co‐polymer PBnDT‐TEET demonstrates the highest recyclability potential with a single dimethyl ester‐functionalized product with an excellent 92 % isolated yield, which can then be repolymerized to reobtain PBnDT‐TEET with a 36 % yield. This work provides a framework towards achieving recyclable organic semiconductors to reduce E‐waste. Although the incorporation of ester linkers allowed for closed‐loop recycling, the low solar cell efficiency of PBnDT‐TEET highlights the significant challenge in achieving both recycling and high device performance.
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- Award ID(s):
- 2134664
- PAR ID:
- 10553763
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemSusChem
- Volume:
- 18
- Issue:
- 3
- ISSN:
- 1864-5631
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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