Helene PUNG1, Celso Yassuo OKADA-JUNIOR2, Mirella SIMOES SANTOS3, Sébastien LIVI2, Jannick DUCHET-RUMEAU2, Agilio PADUA3, Marta MIROLO4, Jakub DRNEC4, Veijo HONKIMAKI4, Patrice RANNOU5, Manuel MARECHAL1
1UMR5819-SyMMES (CNRS/CEA/UGA/Grenoble-INP), Grenoble, France
2UMR5223-IMP (CNRS/INSA Lyon/Univ. Jean Monnet/Univ. Lyon I), Lyon, France
3UMR5182-LCH (CNRS/Laboratoire de Chimie/ENS de Lyon), Lyon, France
4ESRF, The European Synchrotron, Grenoble, France
5UMR5279-LEPMI (CNRS/Grenoble-INP/UGA/USMB), Saint-Martin-d'Hères, France
Ionic Liquids (ILs) belong to a fascinating class of materials intensively studied and developed both for their fundamental interests and a hand full of technological applications due to their unique combination of tunable-by-design properties such as low vapour pressure and flammability, high thermal and (electro)chemical stabilities, and ionic conductivity, to name a few. Encoding a liquid crystalline behaviour into the chemical structures of ILs allows for the dawn of stimuli-responsive (dynamically self-assembling/healing) functional materials, i.e. Thermotropic Ionic liquid Crystals (TILCs). Interestingly, the ‘material marriage’ of ILs with thermotropic liquid crystals (TLCs) opens an exploratory research arena both for (i) in depth (fundamental) studies of the interplay linking the hierarchical self-assembly of functional soft matter into precise morphologies and (1D/2D/3D) dimensionality-controlled ionic transport properties and (ii) their technological uses as a key-enabling sub-component (i.e. the electrolyte) at the heart of new generations of safer-by-design (electrochemical) energy storage and conversion devices such as batteries & supercapacitors, and fuel cells, respectively.
In this communication, we will detail the molecular design strategy, syntheses, and multi-scale structure/ionic transport correlations of a series of anionic conductors (A-TILCs) based on a di-n-octadecylimidazolium (C18C18Im+) cation with four anions, namely iodide [I-], bromide [Br-], bis(trifluoromethane)sulfonimide [TFSI-], and dicyanamide [N(CN)2-]: See Figure. Relying on cross-fertilizing DSC, POM, SAXS/WAXS characterizations and coarse-grain simulations, we will show that this series of A-TILCs share a lamellar organization (smectic A (SmA) mesophase) with ionophobic and ionophilic slabs encoding tuneable-by-design and nanoconfined 2D ionic transport. As reflected in their tuneable transition temperatures and ionic conductivity values (EIS), we will discuss how anion metathesis is authorizing the fine-tuning of the ionic conductivity of A-TILCs. Finally, we will address the role of magnetic field to master mosaicity vs. long range order in A-TILCs (through on-demand control of their dynamic self-assembly). To elaborate on the (growing) interest for self-healing into next generation energy storage/conversion devices through the application of a selected stimulus, we will detail the results of in situ synchrotron-based SAXS/WAXS(T) and EIS(T) combined characterizations, performed with vs. without magnetic field (tunable from 0 till 1T), on A-TILCs infiltrated within LC cells, leveraging the potential of (a customized state-of-the-art sample environment) the ID31 beamline at ESRF.
Acknowledgments: We are indebted to the French National Agency of Research (ANR) for the funding of the collaborative research project CITADEL under the grant ANR-19-CE05-0028. HP, MM & PR express their gratitude to CNRS & UGA for the support of the related research activities within the (Joint Research Unit) UMR5819-SyMMES & UMR5279-LEPMI labs. The coauthors acknowledge ESRF for beamtime allocation at ID31 under the SC-5292 proposal (DOI: 10.15151/ESRF-ES-894751246).