We have investigated structure and relaxation phenomena for ionic liquids 1-octyl-3-methylimidazolium hexafluorophosphate (C8mimPF6) and bis(trifluoromethylsulfonyl)imide (C8mimTFSI) by means of neutron diffraction and neutron spin echo (NSE) techniques. The diffraction patterns show two distinct peaks appeared at scattering vectors Q of 0.3 and 1.0 Å(-1). The former originates from the nanoscale structure characteristic to ionic liquids and the latter due to the interionic correlations. Interestingly, the intensity of the low-Q peak drastically grows upon cooling and keeps growing even below the glass transition temperature. The NSE measurements have been performed at these two Q positions, to explore the time evolution of each correlation. The relaxation related to the ionic correlation (ionic diffusion) is of Arrhenius-type and exhibits nonexponential behavior. The activation energy (Ea) of the ionic diffusion, which is linked to viscosity, depends on the type of anion; the larger is the anion size, the smaller Ea becomes for most of anions. On the other hand, two kinds of relaxation processes, slower and faster ones, are found at the low-Q peak position. The most significant finding is that the fraction of the slower relaxation increases and that of the faster one decreases upon cooling. Combining the NSE data with the diffraction data, we conclude that there exist two parts in ILs: one with the ordered nanostructure exhibiting the slow relaxation, and the other with disordered structure showing faster relaxation. The structure and dynamics of ILs are heterogeneous in nature, and the fraction of each part changes with temperature.

We report a new class of polymer electrolytes that exhibit high Li + -ionic conductivity and thermal stability up to 200 °C. The polymer electrolyte consists of a solvate ionic liquid ([Li(G4)][TFSA]), comprising an equimolar mixture of lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) and tetraglyme (G4), and a well-defined ABA-triblock copolymer, polystyrene-b-poly(methyl methacrylate)-b-polystyrene (PStb-PMMA-b-PSt, SMS). The electrolyte is formed by the selfassembly of SMS, where the solvatophobic PSt segments serves as physical cross-linking points, and the solvatophilic PMMA segment with preferentially dissolved [Li(G4)][TFSA] forms ion-conduction paths. In the electrolyte, the preservation of the complex cation [Li(G4)] + in the PMMA phase was demonstrated by pulsed-field gradient spin−echo (PGSE) NMR, Raman spectra, and thermogravimetric analysis. Because of the preservation of [Li(G4)] + , which hinders the direct interaction of Li + with the polymer segment and the coupling of the ionic transport from the segmental motion, the room temperature ionic conductivity of the electrolyte reached an appreciable level (10 −4 −10 −3 S cm −1 ).

Keywords: solvate ionic liquid polymer electrolyte polymer-in-salt ionicity glyme A B S T R A C T Polymer electrolytes (PEs) have served as the focus of intensive research as new ion-conducting materials, especially for lithium battery applications. A new strategy to develop fast lithium-conducting PEs is reported here. The thermal, ionic transport, and electrochemical properties of polymer solutions in a glyme-Li salt solvate ionic liquid, [Li(G4) 1 ][TFSA], composed of an equimolar mixture of lithium bis (trifluoromethanesulfonyl) amide (Li[TFSA]) and tetraglyme (G4), were characterized. Poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), and poly(butyl acrylate) (PBA) were combined with [Li(G4) 1 ][TFSA] in order to explore the effects of polymer structure on the properties. The self-diffusion coefficient ratio of the glyme and Li + ions (D G /D Li ) was investigated to evaluate the stability of the complex (solvate) cations. The D G /D Li values suggested that the [Li(G4) 1 ] + complex cations underwent a ligand exchange reaction between G4 and PEO in the PEO-based solution, whereas the cations remained stable (D G /D Li = 1) in the PMMA-and PBA-based solutions. The robustness of the [Li(G4) 1 ] + complex cations in the PMMA-and PBA-based solutions was reflected in high weight-loss temperature, greater Li transference number, and high oxidative stability.Owing to the lower glass transition temperature and low affinity towards Li + ions, the PBA-based solutions yielded superior lithium transport properties (ionic conductivity of 10 À4 $10 À3 Scm À1 and Li transference number as high as 0.5) among the investigated polymer solutions.

We describe a functional soft material that can spontaneously repair damage by straightforward application of light illumination. The composite material is composed of a common ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate ([C 4 mim]PF 6 ), and a well-defined ABA triblock copolymer consisting of the IL-compatible poly-(ethylene oxide) (PEO) middle block with thermo-and photosensitive random copolymers combining N-isopropylacrylamide (NIPAm) and 4-phenylazophenyl methacrylate (AzoMA) including azobenzene chromophore as terminal A blocks. The composite shows a sol−gel transition under UV light (366 nm, 8 mW cm −2 ) irradiation at 47°C, whereas that observed under visible light (437 nm, 4 mW cm −2 ) is 55°C, due to the difference in photochromic states of the azobenzene unit. The ABA triblock copolymer undergoes a reversible gel−sol−gel transition cycle at the bistable temperature (53°C), with a reversible association/fragmentation of the polymer network resulting from the photoinduced self-assembly of the ABA triblock copolymer in [C 4 mim]PF 6 . A damaged ABA ion gel shows a remarkable photohealing ability based on drastic changes in the fluidity of the polymer−IL composite triggered by light illumination. The damaged part is successfully repaired by shining UV light resulting in solubilization to fill the crack, followed by gelation to fix the crack triggered by visible light illumination. Tensile tests confirmed the excellent recovery efficiency of the resultant photohealed ABA ion gel, which was as high as 81% fracture energy relative to the original sample. The flexible, selfsupported ABA ion gel is designed for various applications to exhibit not only photohealing ability to improve operating lifetime of the material but also specific functionalities imparted by the IL, such as high ion conductivity, thermal stability, and (electro)chemical stability. ■ INTRODUCTIONSelf-healable materials that can be repaired after being damaged are crucial to improve reliability, functionality, and operating lifetime for many industrial products. In polymeric materials, a traditional approach to repair damage involves liquefying the material by heating it to a temperature above its glass transition temperature (T g ) or melting point (T m ). 1−4 The contacting polymer interface then allows for surface rearrangement in the cracked area, followed by wetting between surfaces, and finally diffusion and re-entanglement of polymer chains. In more recent advances, there have been many strategies aimed at establishing self-healing materials based on precisely controlled molecular building blocks that involved noncovalent linkages such as hydrogen bonds, 5−8 Coulombic interactions, 9 π−π interactions, 10 hydrophobic hydration, 11 and metal−ligand coordination. 12−15 Although such methodologies allow damage recovery by straightforward physical contact, it can be difficult to control the repair precisely in terms of timing or position. A photo stimulus can be an effective external trigger to induce molecular self-a...

The reversible micellization and sol-gel transition of block copolymer solutions in an ionic liquid (IL) triggered by a photostimulus is described. The ABA triblock copolymer employed, denoted P(AzoMA-r-NIPAm)-b-PEO-b-P(AzoMA-r-NIPAm)), has a B block composed of an IL-soluble poly(ethylene oxide) (PEO). The A block consists of a random copolymer including thermosensitive N-isopropylacrylamide (NIPAm) units and a methacrylate with an azobenzene chromophore in the side chain (AzoMA). A phototriggered reversible unimer-to-micelle transition of a dilute ABA triblock copolymer (1 wt%) was observed in an IL, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6), at an intermediate "bistable" temperature (50 °C). The system underwent a reversible sol-gel transition cycle at the bistable temperature (53 °C), with reversible association/fragmentation of the polymer network resulting from the phototriggered self-assembly of the ABA triblock copolymer (20 wt%) in [C4 mim]PF6.