Microphase-separated structures of ion gels consisting of ABA-type block copolymers and an ionic liquid: A key to escape from the trade-off between mechanical and transport properties. (7th October 2020)

• Record Type: Journal Article
• Authors: Mizuno, Haruna; Hashimoto, Kei; Tamate, Ryota; Kokubo, Hisashi; Ueno, Kazuhide; Li, Xiang; Watanabe, Masayoshi
• Is Part Of: Polymer. Volume 206(2020)
• Publication Date: 2020-10-07
• Subjects: Ionic liquid -- Block copolymer -- Microphase separation -- Ionic conductivity -- Mechanical property -- ORCID; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2020.122849
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Upon combination of an ionic liquid (IL) with an amphiphilic ABA-type triblock copolymer, the insoluble A blocks aggregate to form mechanical frameworks and the soluble B blocks form ion-transport paths by incorporating the IL. Consequently, a self-standing ion gel, exhibiting the characteristic high ionic conductivity of ILs, can be obtained. In this study, we investigated the effect of microstructures formed by the block copolymer (spherical, cylindrical, gyroid, and lamellar structures) on the ionic conductivity and mechanical properties of the ion gel by focusing on the microstructures. As a result, an ion gel that formed an isotropic bicontinuous structure was successfully obtained via a heat-induced order-order transition. The structure was maintained even at room temperature, and the ion gel having a bicontinuous structure exhibited favorable mechanical properties (storage modulus, G' ~ 1.0 MPa) and good ionic conductivity ( σ ~ 0.1 mS cm −1 ). In contrast, the ion gels having anisotropic structures (cylindrical structure) exhibited weaker mechanical properties and lower ionic conductivity. The characteristics of bicontinuous structures may be the key to resolving the trade-off between mechanical and transport properties of electrolyte materials for electrochemical devices. Graphical abstract: Image 1 Highlights: Bicontinuous structures are obtained from other microstructures by thermal transition. Bicontinuous structures enable high ionic conductivity with low tortuosity and favorable mechanical properties. Ion gels with bicontinuous structures are suitable for electrochemical devices.