2000 Fiscal Year Final Research Report Summary
HELICAL CONJUGATED POLYMER SYNTHESIZED WITH A CHIRAL NEMATIC REACTION FIELD AND ITS PROPERTIES
| Project/Area Number |
11650919
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
高分子構造・物性(含繊維)
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| Research Institution | UNIVERSITY OF TSUKUBA |
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Principal Investigator |
PIAO Guangzhe University of Tsukuba, Institute of Materials Science, Research Associate, 物質工学系, 助手 (20302391)
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| Co-Investigator(Kenkyū-buntansha) |
AKAGI Kazuo University of Tsukuba, Institute of Materials Science, Professoru, 物質工学系, 教授 (20150964)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Polyacetylene / Helical structure / Chiral nematic liquid crystal / Molecular solenoid / Conjugated polymer / Conducting polymer / Chiral dopant / Asymmetric and anisotropic reaction field |
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| Research Abstract |
We have synthesized for the first time helical polyacetylene with left-and right-handed screw structures under chiral nematic reaction field. The screw direction of the (R)-and (S)-chiral nematic LCs is identified by miscibility test with a well-known right-handed chiral nematic LC, 3-chlorocholest-5-ene. The results demonstrate that they possessed left-handed and right-handed helical structures, respectively. By virtue of its helical structure, the chiral nematic LC is expected to serve as a medium which provides a asymmetric and anisotropic reaction filed for acetylene polymerization and the polyacetylene synthesized under (R)-or (S)-chiral nematic LCs to be chiral, based on a predominant left-handed or right-handed helical sense. It shows that the polyacetylene films synthesized under (R)-or (S)-chiral nematic LCs form helical fibrillar morphologies with left-handed and right-handed directions. respectively. The screw directions of the fibrils coincide with those of the chiral nematic LCs used as solvent. Namely, the twisted directions of the polyacetylene fibril are identical with the corresponding those of the chiral nematic LCs. In circular dichroism (CD) spectra, positive or negative Cotton effect is observed in the region of π→π^* transition of polyacetylene chain, in spite of no existence of chiroptical substituent in side chains. It is evident that the main chain itself is also helically screwed, too. The results mean that these helical chains are bundled through van der Waals interaction to form helical fibrils. It is worthy of remark that the present polyacetylene films showed high electrical conductivities of 1.5×10^3 S/cm after an iodine doping as well as high trans content of 80-90%. Such a helical polyacetylene with high electrical conductivity could serve as a "molecular solenoid" composed of electrically conducting molecular wire.
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