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  From branched polyphenylenes to graphite ribbons

Wu, J. S., Gherghel, L., Watson, M. D., Li, J., Wang, Z. H., Simpson, C. D., et al. (2003). From branched polyphenylenes to graphite ribbons. Macromolecules, 36(19), 7082-7089.

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 Creators:
Wu, J. S.1, Author           
Gherghel, L.1, Author           
Watson, Mark D.1, Author           
Li, J., Author
Wang, Z. H.1, Author           
Simpson, C. D.1, Author           
Kolb, U., Author
Müllen, Klaus1, Author           
Affiliations:
1MPI for Polymer Research, Max Planck Society, ou_1309545              

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 Abstract: This article presents the synthesis of graphitic nanoribbons (~1 nm wide), containing extended conjugated all-benzenoid segments. These were obtained by intramolecular oxidative cyclodehydrogenation of soluble branched polyphenylenes 6, which were prepared by repetitive Diels-Alder cycloaddition of 1,4-bis(2,4,5-triphenylcyclopentadienone-3-yl)benzene (1) and diethynylterphenyl (5) in good yield. While insolubility of the obtained graphite ribbons 7 precluded standard spectroscopic structure elucidation, the electronic and vibrational properties were probed by solid-state UV-vis, Raman, and infrared spectroscopy. A wide and unstructured absorption band covering the visible range of the electronic spectrum (λmax~800 nm) is observed, confirming the highly extended conjugated framework. The structure proof of the ribbon-type polymer is supported by the inclusion of appropriate model compounds. The profile of the visible Raman spectrum of the material is similar to that of a discrete polycyclic aromatic hydrocarbon (PAH) C222H42, characterized by two strong bands (at 1603 and 1322 cm⁻¹), corresponding to the G and D bands of graphite. The obtained graphite ribbons are not linear but rather contain "kinks" due to the structural design of the polyphenylene precursor. High-resolution transmission electron microscopy (HRTEM) images of the graphite ribbons 7 disclose two different domains: one is an ordered graphite layer structure with a layer distance of ca. 3.8 Å, and one is disordered due to the existence of "kinks" in the obtained polymers and/or random stacking of graphite ribbons. Attempts to make linear analogues are so far unsuccessful, emphasizing the critical importance of the geometry of the polyphenylene scaffold to successful oxidative cyclodehydrogenation.

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Language(s): eng - English
 Dates: 2003
 Publication Status: Issued
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 Rev. Type: -
 Identifiers: eDoc: 42956
Other: P-03-47
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Title: Macromolecules
Source Genre: Journal
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Pages: - Volume / Issue: 36 (19) Sequence Number: - Start / End Page: 7082 - 7089 Identifier: -