Synthesis of Chiral Liquid-Crystalline Ionic Liquid and It's Application for Asymmetric Electrochemical Polymerization

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K22221
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 35:Polymers, organic materials, and related fields
• Research Institution: Ritsumeikan University
• Principal Investigator: Akagi Kazuo 立命館大学, 総合科学技術研究機構, 教授 (20150964)
• Project Period (FY): 2019-06-28 – 2021-03-31
• Keywords: 液晶性イオン液体 / イオン性液晶 / 不斉電気化学重合 / ヘリカル共役ポリマー / 酸化・還元状態

Outline of Final Research Achievements

Two types of chiral nematic liquid-crystalline ionic liquids (N*-LCILs) were developed to achieve asymmetric electrochemical polymerization without a supporting electrolyte and even a chiral dopant. N*-LCILs are prepared i) by adding an axially chiral binaphthyl derivative as an external chiral dopant to imidazolium cation-based LCILs or ii) by incorporating a chiral binaphthyl phosphate as a counter anion in LCILs. Helical poly(3,4-ethylenedioxythiophene) (H-PEDOT) films were successfully synthesized through electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) monomer in an N*-LCIL, where N*-LCIL plays the role of both an asymmetric solvent and a supporting electrolyte. H-PEDOT films have helically π-stacked structures of conjugated chains and spiral morphologies consisting of one-handed screwed fibril bundles. The two present types of N*-LCILs are the first to enable supporting electrolyte-free asymmetric electrochemical polymerization.

Free Research Field

高分子化学、液晶化学、物質化学

Academic Significance and Societal Importance of the Research Achievements

従来の電気化学重合ではイオン伝導を確保するため、支持電解質の使用が必須であった。しかし、支持電解質は、嵩高くかつ極性が高いためポリマーから完全に取り除くことは難しく、導電性や光物性を低下させる要因となっている。本重合法は、イオン液体のイオン伝導性を利用するため、電荷担体としての支持電解質を用いる必要はなく、画期的な重合法と位置づけられる。また、イオン液体に液晶性やキラル液晶性を付与することにより、イオン液体の応用範囲が格段に拡大した。特に、液晶性やキラル液晶性を有するイオン液体は、より先進的な電気化学合成に応用でき、低分子化合物の配向や不斉合成にも役立つと期待される。