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http://hdl.handle.net/10773/20985
Título: | The effect of n vs. iso isomerization on the thermophysical properties of aromatic and non-aromatic ionic liquids |
Autor: | Rodrigues, Ana S. M. C. Almeida, Hugo F. D. Freire, Mara G. Lopes-da-Silva, Jose A. Coutinho, Joao A. P. Santos, Luis M. N. B. F. |
Palavras-chave: | ALKYL SIDE-CHAINS THERMODYNAMIC PROPERTIES HEAT-CAPACITY SURFACE TENSIONS PHYSICOCHEMICAL PROPERTIES PHYSICAL-PROPERTIES 1-BUTYL-1-METHYLPYRROLIDINIUM BIS(TRIFLUOROMETHYLSULFONYL)IMIDE IMIDAZOLIUM TEMPERATURE CATION |
Data: | 2016 |
Editora: | ELSEVIER SCIENCE BV |
Resumo: | This work explores the n vs. iso isomerization 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 behaviour, heat capacities, densities, refractive indices, surface tensions, and viscosities. The results here reported show that the presence of the iso-alkyl group leads to an increase of the temperature of the glass transition, T-g. The isopyrrolidinium (5 atoms ring cation core) and iso-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 then and iso-alkyl isomers. A small increase of the surface tension was observed for the non-aromatic Its, which could be related to their higher cohesive energy of the bulk, while the lower surface entropy observed for the iso isomers indicates a structural resemblance between the IL bulk and surface. The significant differentiation between ILs with a 5 and 6 atoms ring cation in the n-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, and iso-alkyl isomers were found to be the most viscous among the studied Its due to their higher energy barriers for shear stress. (C) 2016 Published by Elsevier B.V. |
Peer review: | yes |
URI: | http://hdl.handle.net/10773/20985 |
DOI: | 10.1016/j.fluid.2016.04.009 |
ISSN: | 0378-3812 |
Versão do Editor: | 10.1016/j.fluid.2016.04.009 |
Aparece nas coleções: | CICECO - Artigos |
Ficheiros deste registo:
Ficheiro | Descrição | Tamanho | Formato | |
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The effect of n vs. iso isomerization on the thermophysical properties of aromatic and non-aromatic ionic liquids_10.1016j.fluid.2016.04.009.pdf | 2.17 MB | Adobe PDF |
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