| Research Abstract |
Helical polyacetylene recently developed is anticipated to show novel electromagnetic and optical properties. Recently we synthesized for the first time helical polyacetylene films with left- and right-handed screw structures under chiral nematic reaction field. Here, we extended the synthesis of helical polyacetylene by developing the following approaches shown below.
(1) Novel chiral titanium complexes as chiral dopants with catalytic activity for synthesis of helical polyacetylene : We synthesized a series of chiral titanium complexes with chiral center-containing groups or axially chiral 1,1'-binaphthyl ones as coordination ligands, to develop catalytically active chiral dopants feasible for the asymmetric polymerization of acetylene. It is found that these complexes induce chiral nematic (N^*) phase when dissolved in a mixture of two nematic liquid crystals (LCs) and can polymerize acetylene to give helical polyacetylene with an aid of Et_3Al used as a co-catalyst under the N^* LC.
(2) Synthesis of Vertically Aligned Helical Polyacetylene Films in Homeotropic Chiral Nematic Liquid Crystals : We constructed a novel homeotropic N^* LC reaction field for synthesis of vertically aligned helical PA film. The homeotropic N^* LC was prepared by adding chiral dopant, (R)- or (S)-PCH506-binol and (R)- or (S)-PCH308^* into the homeotropic nematic LCs consisting of PCH506 + (PCH30))_26, PCH506 + (PCH50))_26, and PCH506 + (PCH50)_28. Scanning electron microscope (SEM) measurements showed twisted polyacetylene fibrils are grown parallel to the direction of film thickness, giving vertically aligned helical fibrillar morphology.
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