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Dynamics and ionic conductivity of ionic liquid crystals forming a hexagonal columnar mesophase

  • For the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflate ionic liquid crystals (ILCs) having different length of alkyl chains were investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). By self-assembly, these ILCs can form a hexagonal ordered mesophase besides plastic crystalline phases and the isotropic state. Three dielectric active processes were found by BDS for both samples. At low temperatures, a γ-process in the plastic crystalline state is observed which is assigned to localized fluctuations of methyl groups including nitrogen atoms in the guanidinium head. At higher temperatures but still in the plastic crystalline state, an α1-process takes place. An α2 process was detected by SHS but with a completely different temperature dependence of the relaxation times than that of the α1-relaxation. This result is discussed in detail, and different molecular assignments of the processesFor the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflate ionic liquid crystals (ILCs) having different length of alkyl chains were investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). By self-assembly, these ILCs can form a hexagonal ordered mesophase besides plastic crystalline phases and the isotropic state. Three dielectric active processes were found by BDS for both samples. At low temperatures, a γ-process in the plastic crystalline state is observed which is assigned to localized fluctuations of methyl groups including nitrogen atoms in the guanidinium head. At higher temperatures but still in the plastic crystalline state, an α1-process takes place. An α2 process was detected by SHS but with a completely different temperature dependence of the relaxation times than that of the α1-relaxation. This result is discussed in detail, and different molecular assignments of the processes are suggested. At even higher temperatures, electrical conductivity is detected and an increase in the DC conductivity by four orders of magnitude at the phase transition from the plastic crystalline to the hexagonal columnar mesophase is found. This result is traced to a change in the charge transport mechanism from a delocalized electron hopping in the stacked aromatic systems (in the plastic phase) to one dominated by an ionic conduction in the quasi-1D ion channels formed along the supermolecular columns in the ILCs hexagonal mesophases.zeige mehrzeige weniger

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Autor*innen:Arda Yildirim, Paulina SzymoniakORCiD, K. Sentker, M. Butschies, A. Bühlmeyer, P. Huber, S. Laschat, Andreas SchönhalsORCiD
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Physical Chemistry Chemical Physics
Jahr der Erstveröffentlichung:2018
Organisationseinheit der BAM:6 Materialchemie
6 Materialchemie / 6.6 Physik und chemische Analytik der Polymere
Verlag:Royal Society of Chemistry
Jahrgang/Band:20
Ausgabe/Heft:8
Erste Seite:5626
Letzte Seite:5635
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Ionic liquid crystalls
Themenfelder/Aktivitätsfelder der BAM:Material
DOI:10.1039/c7cp08186c
ISSN:1463-9084
ISSN:1463-9076
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:21.02.2018
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:21.02.2018
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