The Effect ofnvs.isoIsomerization on the Thermophysical Properties of Aromatic and Non-aromatic Ionic Liquids.
This work explores thenvs.isoisomerization effects on the physicochemical properties of different families of ionic liquids (ILs) with variable aromaticity and ring size. This study comprises the experimental measurements, in a wide temperature range, of the ILs' thermal behavior, heat capacities, densities, refractive indices, surface tensions, and viscosities. The results here reported show that the presence of theiso-alkyl group leads to an increase of the temperature of the glass transition,Tg. Theiso-pyrrolidinium (5 atoms ring cation core) andiso-piperidinium (6 atoms ring cation core) ILs present a strong differentiation in the enthalpy and entropy of melting. Non-aromatic ILs have higher molar heat capacities due to the increase of the atomic contribution, whereas it was not found any significant differentiation between thenandiso-alkyl isomers. A small increase of the surface tension was observed for the non-aromatic ILs, which could be related to their higher cohesive energy of the bulk, while the lower surface entropy observed for theisoisomers indicates a structural resemblance between the IL bulk and surface. The significant differentiation between ILs with a 5 and 6 atoms ring cation in then-alkyl series (where 5 atoms ring cations have higher surface entropy) is an indication of a more efficient arrangement of the non-polar region at the surface in ILs with smaller cation cores. The ILs constituted by non-aromatic piperidinium cation, andiso-alkyl isomers were found to be the most viscous among the studied ILs due to their higher energy barriers for shear stress.
CIQUP, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687, P-4169-007 Porto, Portugal.
Ana S M C
AS
Rodrigues
CICECO, Departamento de Química, Universidade de Aveiro, P-3810-193 Aveiro, Portugal.
Hugo F D
HF
Almeida
CICECO, Departamento de Química, Universidade de Aveiro, P-3810-193 Aveiro, Portugal.
Mara G
MG
Freire
QOPNA, Departamento de Química, Universidade de Aveiro, P-3810-193 Aveiro, Portugal.
José A
JA
Lopes-da-Silva
CICECO, Departamento de Química, Universidade de Aveiro, P-3810-193 Aveiro, Portugal.
João A P
JA
Coutinho
CIQUP, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687, P-4169-007 Porto, Portugal.
Luís M N B F
LM
Santos
Bis(trifluoromethylsulfonyl)imide; Density; Differential Scanning Calorimetry; Glass Transition; Heat capacity; Imidazolium; Ionic liquids; Isomerization; Phase Behavior; Piperidinium; Pyridinium; Pyrrolidinium; Refractive Index; Surface Tension; Viscosity
Acc Chem Res. 2007 Nov;40(11):1182-92
17979252
Chem Soc Rev. 2008 Jan;37(1):123-50
18197338
J Phys Chem B. 2015 Nov 25;119(47):14934-44
26505274
J Chem Phys. 2014 Feb 14;140(6):064505
24527930
J Phys Chem B. 2013 Sep 19;117(37):10889-97
23915346
Langmuir. 2014 Jun 10;30(22):6408-18
24834955
J Colloid Interface Sci. 2007 Oct 15;314(2):621-30
17604038
J Phys Chem B. 2008 Mar 13;112(10):3077-84
18271576
J Phys Chem B. 2005 Apr 7;109(13):6103-10
16851672
Phys Chem Chem Phys. 2015 Nov 11;17(45):30328-42
26506981
Chemphyschem. 2002 Feb 15;3(2):161-6
12503123
J Phys Chem B. 2013 Dec 12;117(49):15328-37
23750608
Chemphyschem. 2016 May 18;17(10):1512-7
26888172
J Phys Chem B. 2012 Feb 23;116(7):2059-64
22268500
Top Curr Chem. 2010;290:185-212
21107798
J Am Chem Soc. 2005 Sep 7;127(35):12192-3
16131175