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Abstract Organic semiconducting donor–acceptor polymers are promising candidates for stretchable electronics owing to their mechanical compliance. However, the effect of the electron‐donating thiophene group on the thermomechanical properties of conjugated polymers has not been carefully studied. Here, thin‐film mechanical properties are investigated for diketopyrrolopyrrole (DPP)‐based conjugated polymers with varying numbers of isolated thiophene moieties and sizes of fused thiophene rings in the polymer backbone. Interestingly, it is found that these thiophene units act as an antiplasticizer, where more isolated thiophene rings or bigger fused rings result in an increased glass transition temperature (Tg) of the polymer backbone, and consequently elastic modulus of the respective DPP polymers. Detailed morphological studies suggests that all samples show similar semicrystalline morphology. This antiplasticization effect also exists inpara‐azaquinodimethane‐based conjugated polymers, indicating that this can be a general trend for various conjugated polymer systems. Using the knowledge gained above, a new DPP‐based polymer with increased alkyl side chain density through attaching alky chains to the thiophene unit is engineered. The new DPP polymer demonstrates a record lowTg, and 50% lower elastic modulus than a reference polymer without side‐chain decorated on the thiophene unit. This work provides a general design rule for making low‐Tgconjugated polymers for stretchable electronics.
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Regio‐regular and cross‐conjugated poly(thienylene vinylene)s through acyclic diene metathesis
Abstract Poly(thienylene vinylene)s (PTV's) are early examples of conjugated polymers but have not been extensively studied when compared with closely analogous polythiophenes. PTV's synthesized through previously reported techniques are similar in structures that contain various alkyl or alkoxy side‐chains that exert limited impact on the polymer electronic properties. Herein, we report the preparation of a series of regio‐regular PTV's (rr‐PTV's) bearing cross‐conjugated side‐chains through ADMET polymerization of a common brominated di(thienylene vinylene) (DTV) monomer followed by PPM reactions on the resulting brominated PTV. These new polymers contain a bulky silyloxy alkyl side‐chain and a functionalized thiophene moiety on every main‐chain thiophene unit, and their regio‐regular placement is confirmed by NMR spectroscopy. The thienyl based side‐groups broaden polymer absorption ranges and at the same time lead to uncommon emission properties that are results of light‐induced charge transfer events between the polymer main‐chains and side‐chains. Removal of the silyl groups on one of these rr‐PTV's led to insoluble materials and x‐ray diffraction experiments on the collected solids displayed distinct scattering peaks that are absent from similarly functionalized regio‐random PTV's reported previously, thus suggesting better crystallinity originated from regio‐regularity.
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- Award ID(s):
- 2101535
- PAR ID:
- 10362904
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Polymer Science
- Volume:
- 60
- Issue:
- 4
- ISSN:
- 2642-4150
- Page Range / eLocation ID:
- p. 650-657
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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