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Journal Article

Synthesis and characterization of a helical step-ladder polyarylene


Lehmann,  Christian W.
Service Department Lehmann (EMR), Max-Planck-Institut für Kohlenforschung, Max Planck Society;

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Nehls, B. S., Galbrecht, F., Brauer, D. J., Lehmann, C. W., Scherf, U., & Farrell, T. (2006). Synthesis and characterization of a helical step-ladder polyarylene. Journal of Polymer Science, Part A: Polymer Chemistry, 44(19), 5533-5545. doi:10.1002/pola.21552.

Cite as: https://hdl.handle.net/11858/00-001M-0000-000F-9463-5
A helical step‐ladder polyarylene incorporating chiral (R)‐2,2′‐dioctoxy‐1,1′‐binaphthyl units was synthesized for the first time. The first step involved the preparation of a precursor poly(arylene ketone) via a palladium‐mediated Suzuki‐type cross‐coupling reaction with the aid of microwave heating. Two polymer‐analog reaction steps, the reduction of the keto groups to tertiary alcohol functionalities and subsequent intramolecular Friedel–Crafts cyclization, gave a step‐ladder polymer (6) in good yields with reasonable mean average molecular weights greater than 13,000. The regioselective cyclization pattern in the α position of the naphthalene core was confirmed by a comparison of the NMR data of the polymer with those of the corresponding model ladder oligomers, 12 and 13, and also a single‐crystal structure of 13. The optical spectra of the oligomers and polymers indicated that there was little electronic interaction across the binaphthyl units. The circular dichroism spectrum of 6 exhibited a strong bisignate Cotton effect in the π–π* absorption region of the planar chromophores, which reflected the strong exciton coupling within the helical polymer chain.