Chiroptical properties of poly(p-phenyleneethynylene) copolymers in thin films: large g-values.
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.
Wilson
James N
JN
Department of Chemistry and Biochemistry, The University of South Carolina, Columbia, South Carolina 29208, USA.
Steffen
Winfried
W
McKenzie
Trent G
TG
Lieser
Günter
G
Oda
Masao
M
Neher
Dieter
D
Bunz
Uwe H F
UH