Ionic liquids (ILs), solely composed of cations and anions, are regarded as a novel class of promising liquids, potentially applicable to energy devices, separation materials, etc. ILs have also attracted great attention as new media for molecular self-assembly, capable of producing novel soft materials with unique features never observed for conventional soft materials containing organic and aqueous solvents. Ion gels formed by polymer self-assembly would exhibit excellent mechanical properties and solution processability without impairing the intrinsic properties of ILs, such as non-volatility, gas absorbability, and high ionic conductivity. In this talk, ion gels based on self-assembly of ABA flexible block copolymers and rigid ionomers in ILs will be addressed for applications to lithium-ion battery electrolytes and CO2 separations membranes, respectively. The first topic is the electrochemical properties and battery performance of polymer electrolytes composed of ABA-triblock copolymers and Li-glyme solvate ionic liquids (SILs), which consist of the [Li(glyme)]+ complex cation and bis(trifluoromethanesulfoly)amide ([TFSA]-) anion, to simultaneously achieve high ionic conductivity, thermal stability, and a wide potential window. Self-assembled structures of the block copolymers greatly changed depending on the composition, molecular weight of each segment and structure of the block copolymers. Such variations appear to be rationalized by conventional theory for micro-phase separated structures of block copolymers. By using suitable block copolymers, a 4-V class Li batteries with a LiCoO2 cathode and a Li metal anode could be operated stably. As the second topic, the transport properties of IL/sulfonated polyimide (SPI) composite membranes for CO2 separation in relation to their nanostructures will be presented. These composite membranes enable favorable CO2 separation and surprisingly superior mechanical properties. SPI is plasticized by the IL, which induces a decrease in the elastic modulus; however, due to the formation of bicontinuous nanostructures of IL-rich and SPI-rich phases, a modulus of &gt;10 MPa is retained even with the incorporation of 75 wt% IL. Consequently, the permeation coefficient of CO2 (P) of the membranes increases with increasing IL content without decreasing the separation factor α (CO2/N2), showing P = 431 Barrer and α = 30, still retaining thin-film processability.

Transport of ions and small molecules in self-assembled materials based on polymers and ionic liquids for application in energy and sustainability

2019 Fall National Meeting

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