title: Glass transition dynamics and conductivity scaling in ionic deep eutectic solvents: The case of (acetamide + lithium nitrate/sodium thiocyanate) melts.
abstract: A detailed investigation on the molecular dynamics of ionic deep eutectic solvents (acetamide + lithium nitrate/sodium thiocyanate) is reported. The study was carried out employing dielectric relaxation spectroscopy covering seven decades in frequency (10(-1)-10(6) Hz) and in a wide temperature range from 373 K down to 173 K, accessing the dynamic observables both in liquid and glassy state. The dielectric response of the ionic system has been presented in the dynamic window of modulus formalism to understand the conductivity relaxation and its possible connection to the origin of localized motion. Two secondary relaxation processes appear below glass transition temperature. Our findings provide suitable interpretation on the nature of secondary Johari-Goldstein process describing the ion translation and orientation of dipoles in a combined approach using Ngai's coupling model. A nearly constant loss feature is witnessed at shorter times/lower temperatures. We also discuss the ac conductivity scaling behavior using Summerfield approach and random free energy barrier model which establish the time-temperature superposition principle. These experimental observations have fundamental importance on theoretical elucidation of the conductivity relaxation and glass transition phenomena in molten ionic conductors.
authors.affiliation: Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland.
authors.forename: Satya N
authors.initials: SN
authors.lastname: Tripathy
authors.affiliation: Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland.
authors.forename: Zaneta
authors.initials: Z
authors.lastname: Wojnarowska
authors.affiliation: Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland.
authors.forename: Justyna
authors.initials: J
authors.lastname: Knapik
authors.affiliation: Department of Nanomaterial Science and Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Shirota
authors.affiliation: Department of Chemical, Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata 700098, India.
authors.forename: Ranjit
authors.initials: R
authors.lastname: Biswas
authors.affiliation: Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland.
authors.forename: Marian
authors.initials: M
authors.lastname: Paluch