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From branched polyphenylenes to graphite ribbons

MPG-Autoren
http://pubman.mpdl.mpg.de/cone/persons/resource/persons49022

Wu,  J. S.
MPI for Polymer Research, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons47932

Gherghel,  L.
MPI for Polymer Research, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons48967

Watson,  Mark D.
MPI for Polymer Research, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons48963

Wang,  Z. H.
MPI for Polymer Research, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons48768

Simpson,  C. D.
MPI for Polymer Research, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons48459

Müllen,  Klaus
MPI for Polymer Research, Max Planck Society;

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Zitation

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.


Zitierlink: http://hdl.handle.net/11858/00-001M-0000-000F-630B-7
Zusammenfassung
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.