Synthesis of Helical Polyacetylene and Construction of Molecular Solenoid

新近开发的螺旋聚乙炔有望表现出新的电磁和光学性质。最近，我们首次在手性向列反应场下合成了具有左旋和右旋螺旋结构的螺旋型聚乙炔薄膜。在这里，我们通过发展如下所示的方法扩展了螺旋聚乙炔的合成。(1)新型手性钛配合物作为催化合成螺旋聚乙炔的手性掺杂剂：我们合成了一系列手性含中心基团或轴向手性1,1′-联萘基作为配位体的手性钛配合物，开发了可用于乙炔不对称聚合的具有催化活性的手性掺杂剂。发现这些配合物在两种向列相液晶（LCs）的混合物中溶解时产生手性向列相（N^*），并在N^*液晶下以Et_3Al为助催化剂聚合乙炔生成螺旋型聚乙炔。(2)在同向性手性液晶中合成垂直排列螺旋聚乙炔薄膜：构建了一种新型的同向性N^* LC反应场，用于合成垂直排列螺旋聚乙炔薄膜。在由PCH506 + (PCH30))_26、PCH506 + (PCH50))_26和PCH506 + (PCH50)_28组成的同向列相LC中加入手性掺杂剂(R)-或(S)-PCH506-binol和(R)-或(S)- pch308 ^*，制备了同向性N^* LC。扫描电子显微镜（SEM）测量显示，扭曲的聚乙炔原纤维与膜厚度方向平行生长，形成垂直排列的螺旋状原纤维形态。

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.