Self-Assembled Helical Conjugated Poly(m-phenylene) Derivatives That Afford Whiskers with Hexagonal Columnar Packed Structure

We have synthesized a series of pi-conjugated polymers, poly(m-phenylene) [PMP] derivatives with chiral or racemic alkyl groups in side chains. Peculiar liquid crystalline phases or crystalline structures based on helical conjugated polymer main chains are elucidated. The PMPs synthesized by polymerizations of chiral and racemic monomers are found to self-assemble to form whiskers, so far as the polymers bear secondary alkyl groups with appropriate lengths in side chains. The whiskers have a hexagonal columnar packed structure, and the columns are uniaxially aligned parallel to the long axis of the whisker. The measurements of circular dichroism spectra and X-ray diffractions indicate that the polymers have a one-handed helical structure consisting of helicene-type conjugated main chains. The chiral PMPs show not only linearly polarized fluorescence after the macroscopic alignment but also circularly polarized fluorescence owing to the helical conjugated main chain.