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Chiroptical Properties of Poly( p - phenyleneethynylene) Copolymers in Thin Films: Large g -Values

2002; American Chemical Society; Volume: 124; Issue: 24 Linguagem: Inglês

10.1021/ja026532s

1943-2984

James N. Wilson, Winfried Steffen, Trent G. McKenzie, Günter Lieser, Masao Oda, Dieter Neher, Uwe H. F. Bunz,

Supramolecular Chemistry and Complexes

A series of chirally substituted poly (p-phenyleneethynylene) copolymers was prepared by alkyne metathesis of mixtures of two different 2,5-dialkyl-1,4-dipropynylbenzenes. One of the monomers was the chiral bis-2,5-(S)-3,7-dimethyloctyl-1,4-dipropynylbenzene, and the second one was an achiral dipropynyl monomer. If the content of chiral monomer is 25-50 mol %, unusually large chiroptical effects, that is, optical dissymmetries, result in absorption (g = -0.38) and emission (g = -0.19) of these copolymers. The large dissymmetries can be explained by a supramolecular ordering of the PPEs into stranded features that are visualized by dark-field transmission electron microscopy. The strands of chirally substituted PPEs display a striated structure that suggests that the whole feature is a single chirally twisted crystallite.