Synthesis of Helical Polyacetylene and Construction of Molecular Solenoid

最近开发的螺旋聚乙炔有望显示出新颖的电磁和光学性能。最近，我们首次在手性向列相反应场中合成了具有左旋和右旋螺旋结构的螺旋聚乙炔薄膜。(1)新型手性钛配合物作为手性掺杂剂催化合成螺旋聚乙炔：我们合成了一系列以手性中心基团或轴向手性1，1‘-联萘酮为配位配体的手性钛配合物，以开发出可用于乙炔不对称聚合的催化活性手性掺杂剂。研究发现，这些化合物在两个向列型液晶(LCS)的混合物中形成手性向列型(N^*)相，并能在Et_3Al的辅助下聚合乙炔生成螺旋状聚乙炔。(2)在各向异性手性向列型液晶中合成垂直排列的螺旋聚乙炔薄膜：我们构建了一个新的同质N^*LC反应场来合成垂直排列的螺旋PA薄膜。在由PCH506+(PCH30)26、PCH506+(PCH50)26和PCH506+(PCH50)28组成的向列型液晶中加入手性掺杂剂(R)-或(S)-PCH506-二醇和(R)-或(S)-PCH308^*制备了向列型液晶。扫描电子显微镜(SEM)测量表明，扭曲的聚乙炔纤维平行于薄膜厚度方向生长，形成垂直排列的螺旋状纤维形态。

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.