Authors
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Müller, T.; Mondelli, P.; Losi, T.; Komber, H.; Lombeck, F.; Fazzi, D.; McNeill, C. R.; Caironi, M.; Sommer, M.
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Title
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Methyl group in asymmetric DPP n-type copolymers impedes aggregation and charge transport anisotropy
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Date
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30.11.2023
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Number
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0
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Abstract
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A comparative study of the impact of a single methyl group attached to dithienyl-diketopyrrollopyrrole (ThDPPTh)/tetrafluorobenzene (F4) copolymers on optoelectronic and structural properties is presented. Two monomers with and without a methyl group attached are prepared and used for the direct arylation polycondensation with dibromo-F4 to get two n-type copolymers. The asymmetric monomer with the methyl group is prepared on a ∼8 g scale. The presence of the methyl group leads to significant backbone torsion, strongly improved solubility, and reduced aggregation in solution. The methyl group furthermore reduces the melting point by ∼80 K but does not eliminate crystallinity. Thin films of both materials probed by GIWAXS feature lamellar morphologies with pronounced edge-on orientations, indicating their propensity to order. However, in thin films of the methylated copolymer directionally processed by off-center spin-coating, complete loss of charge transport anisotropy is found along with moderately reduced electron mobilities of 10–2–10–1 cm2/(V s). The study shows that single methyl groups attached to conjugated polymers can have a dramatic impact on properties and that careful placement within the copolymer structure opens up an efficient handle to balance properties related to processing and performance.
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Publisher
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American Chemical Society
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Wikidata
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Citation
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Macromolecules 56 (2023) 9811-9820
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DOI
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https://doi.org/10.1021/acs.macromol.3c01790
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Tags
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