Neue Polymermaterialien auf der Basis von funktionalisierten ionischen Flüssigkeiten für Anwendungen in Membranen
Zusammenfassung der Projektergebnisse
In summary in the current study three polymeric Ionic Liquids (PILs) as well as their monomeric correspondents with systematically varied anion-cation composition are investigated by means of Broadband Dielectric Spectroscopy (BDS), Fourier Transform Infrared Spectroscopy (FTIR), AC-Chip, and Differential Scanning Calorimetry. First, three dielectric active relaxation processes are found; two of them are assigned to secondary fluctuations (τβ1,2) of the individual ion species, whereas the third (τα) originates from relaxations of transient ion pairs and reflects the dynamic glass transition. This relaxation process shows a Vogel-Fulcher-Tammann (VFT) temperaturedependence and scales with the calorimetric glass transition temperature Tg. Second, the complex conductivity of both, low molecular weight and polymeric ILs, is determined by hopping conduction in a spatially and temporally varying random energy landscape. The mean hopping rate ωc is found to be proportional to the relaxation rate of the dynamic glass transition tα and the DC-conductivity σ0, thus proving the validity of the Barton- Namikawa-Nakajima (BNN)-relation for all systems under study in general (in particular for the PILs for higher as well as lower temperatures as the Tσ0). In contrast to the low molecular weight ILs, the thermal activation of the DC-conductivity in the polymeric systems changes from a VFT- into an Arrhenius-dependence at a (sample specific) temperature Tσ0. While in many studies this transition was found to be close to the calorimetric glass transition temperature Tg and hence interpreted a consequence of the dynamic glass trantion, in the present study PILs are examined for which the transition temperature distinctly differs from the calorimetric glass transition temperatures Tg (by as far as 80 K) and the novel transition temperatureTσ0 has to be introduced. The fact that the mean structural relaxation rate time tα, the charge carrier hopping rate ωc, and the DC-conductivity σ0 are proportional to each other well below and above the transition temperature Tσ0 explicitly proves that the mechanism of charge transport is deduced as glassy dynamics assisted hopping conduction and does not change at Tσ0. Third, analysing the temperature dependence of selected moiety-specific IR-active vibrations one observes for all low molecular weight ILs distinct changes of all intramolecular vibrational potentials at Tg. In the case of the polymeric ILs instead, only the thermal activations of vibrational modes adjoining the ionic moieties are changed at Tσ0. Vibrational potentials of neutral moieties as those of the free alkyl-chains or the polymeric backbone are not affected at Tσ0; but at Tg. This leads to the identification of charge transport responsive (CTR) and charge transport irresponsive (CTI) moieties.
Projektbezogene Publikationen (Auswahl)
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“Introduction to Ionic Liquids” in Dielectric Properties of Ionic Liquids, Advances in Dielectrics, (2016), 1 - 27. (Ed. Marian Paluch, Series Ed. Friedrich Kremer) Springer Verlag
Strehmel V.
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“Molecular Dynamics and Charge Transport in Polymeric Polyisobutylene-Based Ionic Liquids”, Macromolecules 49, 2868-2875 (2016)
Frenzel, F., M. Y. Folikumah, M. Schulz, A.M. Anton, W.H. Binder, F. Kremer
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“Molecular Dynamics and Charge Transport in Highly Conductive Polymeric Ionic Liquids”, Macromolecules 50 (10), 4022-4029 (2017)
Frenzel F., R. Guterman, M. Anton, J. Yuan, F. Kremer
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"Charge Transport and Glassy Dynamics in Polymeric Ionic Liquids as reflected by its Inter- and Intramolecular Interactions" Soft Matter 15, 1605-1618 (2019)
Frenzel, F., Borchert, P, Anton, A. M., Strehmel, V., Kremer, F.
