Evidence of nanostructuration from the heat capacities of the 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid series

• Type: Article in International Scientific Journal
• Date: 2013

Authors

Marisa A A Rocha (Author) Other; Joao A P Coutinho (Author) Other; Luis M N B F Santos (Author) FCUP

Journal

Title: Journal of Chemical Physics

Vol. 139

Final page: 104502

ISSN: 0021-9606

Publisher: American Institute of Physics

Indexing

ISI Web of Knowledge - 36 Citations

Scopus - 36 Citations

Scientific classification

FOS: Natural sciences > Physical sciences

Other information

Authenticus ID: P-006-7B0

DOI: 10.1063/1.4820825

Abstract (EN): In the present work, the heat capacities at T = 298.15 K of 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide, [C(N/2)C(N/2)im][NTf2], were measured, for the first time, using a high-precision heat capacity drop calorimeter, with an uncertainty of less than 0.15%. Based on the obtained results, it was possible to evaluate the effect of the cation symmetry on the heat capacity data through a comparative analysis with the [C(N-1)C(1)im][NTf2] ionic liquid series. The molar heat capacities of the [C(N/2)C(N/2)im][NTf2] ionic liquids series present a less pronounced deviation from the linearity along the alkyl chain length than the asymmetric based ionic liquids series. Lower molar heat capacities for the symmetric than the asymmetric series were observed, being this difference more evident for the specific and volumic heat capacities. As observed for the [C(N-1)C(1)im][NTf2] series, a trend shift in the heat capacities at [C(6)C(6)im][NTf2] was found that reflects the impact of nonpolar region nanostructuration on the thermophysical properties of the ionic liquids. The profile of the two regions is in agreement with the expected effect arising from the nanostructuration in ionic liquids. The results obtained in the present work show a clear indication that for the symmetric series, [C(N/2)C(N/2)im][NTf2], the starting of the liquid phase nanostructuration/alkyl chain segregation occurs around [C(6)C(6)im][NTf2]. (C) 2013 AIP Publishing LLC.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 5