Nanostructuration Effect on the Thermal Behavior of Ionic Liquids

• Type: Article in International Scientific Journal
• Date: 2016

Authors

Rodrigues, ASMC (Author) Other; Luis M N B F Santos (Author) FCUP

Journal

Title: ChemPhysChem

Vol. 17

Pages: 1512-1517

ISSN: 1439-4235

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 22 Citations

Scopus - 24 Citations

Other information

Authenticus ID: P-00K-W32

DOI: 10.1002/cphc.201501128

Abstract (EN): This work shows how the nanostructuration of ionic liquids (ILs) governs the glass and melting transitions of the bistriflimide imidazolium-based [C(n)C(1)im][NTf2] and [C(n)C(n)im][NTf2] series, which highlights the trend shift that occurs at the critical alkyl size (CAS) of n=6. An initial increase in the glass temperature (T-g) with an increase in the alkyl side chain was observed due to the intensification of the dispersive interactions (van der Waals). Above the CAS, the -CH2- increment has the same effect in both glass and liquid states, which leads to a plateau in the glass transition after nanostructuration. The melting temperature (T-m) of the [C(n)C(1)im][NTf2] and [C(n)C(n)im][NTf2] series presents a V-shaped profile. For the short-alkyl ILs, the -CH2- increment affects the electrostatic ion pair interactions, which leads to an increase in the conformational entropy. The -CH2- increment disturbs the packing ability of the ILs and leads to a higher entropy value (Delta(s)dagger S-m degrees) and consequently a decrease in T-m. Above the CAS, the -CH2- contribution to the melting temperature becomes more regular, as a consequence of the nanostructuration of the IL into polar and nonpolar domains. The dependence of the alkyl chain on the temperature, enthalpy, and entropy of melting in the ILs above the CAS is very similar to the one observed for the alkane series, which highlights the importance of the nonpolar alkyl domains on the ILs thermal behavior.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 6