Charge transport and glassy dynamics in a room temperature ionic liquid- [BMPyr][TFSI]

• Published in: Journal of non-crystalline solids 2020-08, Vol.541, p.120133, Article 120133
• Main Authors: Safna Hussan, K.P., Thayyil, Mohamed Shahin
• Format: Article
• Language: English
• Subjects: Broadband dielectric spectroscopy; Charge transport; Differential scanning calorimetry; Glassy dynamics; Ionic liquids
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2020.120133

•The molecular mobility and charge transportation of a [BMPyr][TFSI] were investigated using BDS.•DSC thermograms revealed a Tg, Tc and 2 consecutive Tm of [BMPyr][TFSI].•[BMPyr][TFSI] is a fragile intermediate system with fragility index 96.3 and a Tg around 182 K.•A strong translational–rotation coupling were observed due to intermolecular JG relaxation. In this paper, thermal and spectroscopic investigations on a room temperature ionic liquid, 1-Butyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMPyr][TFSI]) were carried out using differential scanning calorimetry and broadband dielectric spectroscopy over wide temperature to study the molecular mobility, charge transport properties, and conductivity relaxation. The quantum mechanical calculations were used to study its polar nature. The isochronal cooling and heating were measured to get an estimation of the glass transition temperature. The study revealed that [BMPyr][TFSI] is an intermediate fragile system with a fragility index of 96.3 and Tg around 182 K. A strong translational–rotation coupling of the [BMPyr][TFSI] molecules were observed in the glassy state due to intermolecular Johari Goldstein relaxation. It showed an excellent agreement with the coupling model predictions. The conductivity behavior of [BMPyr][TFSI] follows Johncher's power law, and its temperature dependence well fits with the Arrhenius equation having an activation energy of 686.3 kJ/mol. The glass transition temperature obtained from DSC, isochronal cooling data and heating data were in good agreement.