| 1. |
- Holomb, Roman, et al.
(författare)
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Ionic liquid structure: the conformational isomerism in 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim][BF4])
- 2008
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 39:7, s. 793-805
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Tidskriftsartikel (refereegranskat)abstract
- As a probe of local structure, the vibrational properties of the 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] ionic liquid were studied by infrared (IR), Raman spectroscopy, and ab initio calculations. The coexistence of at least four [bmim]+ conformers (GG, GA, TA, and AA) at room temperature was established through unique spectral responses. The Raman modes characteristic of the two most stable [bmim] + conformers, GA and AA, according to the ab initio calculations, increase in intensity with decreasing temperature. To assess the total spectral behavior of the ionic liquid both the contributions of different [bmim] + conformers and the [bmim]+- [BF4]- interactions to the vibrational spectra are discussed.
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| 2. |
- Martinelli, Anna, 1978, et al.
(författare)
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A structural study on ionic-liquid-based polymer electrolyte membranes
- 2007
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 154:8, s. G183-G187
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated novel proton conducting membranes synthesized through the gelification of poly(vinylidene fluoride-co-hexafluoropropylene) in aprotic ionic liquids. Mobile protons were introduced by doping the system with the strong bis(trifluoromethanesulfonyl)imide acid (HTFSI), which is chemically compatible with the ionic liquids through the common TFSI- anion. The obtained membranes are thermally stable up to 115°C set by the melting of the polymer phase. At this temperature, the conductivity is on the order of 10-2 S cm-1. Raman and infrared spectroscopy show no chemical interactions between the components, indicating that the bulklike nature of the doped ionic liquids preserved within the membrane, as is the thermal stability and the high conductivity. © 2007 The Electrochemical Society.
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| 3. |
- Martinelli, Anna, 1978, et al.
(författare)
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A study on the state of PWA in PVDF-based proton conducting membranes by Raman spectroscopy
- 2007
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 178:7-10, s. 527-531
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Tidskriftsartikel (refereegranskat)abstract
- Polymer composite proton conducting membranes with increasing amount of tungstophosphoric acid (PWA) have been synthesized starting from poly(vinylidene) fluoride and alumina. Membranes could be prepared with an acid loading up to 16.7 wt.%. The conductivity of the membranes increases with acid loading up to 10- 3 Scm- 1 at the highest loading. The membrane matrices have a good thermal stability up to 240 °C, however a loss of water absorbed during the preparation procedure is observed at a considerably lower temperature. Raman spectroscopy showed that in the membrane the polymer adopts a conformation that could promote a separation into hydrophilic/hydrophobic sites. An interaction between alumina and PWA is also found that might limit the conductivity of the membranes.
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| 4. |
- Martinelli, Anna, 1978, et al.
(författare)
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Conformational evolution of TFSI− in protic and aprotic ionic liquids
- 2011
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Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555.
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Tidskriftsartikel (refereegranskat)abstract
- We here report on the conformational evolution of the bis(trifluoromethanesulfonyl)imide anion (TFSI−) in protic and aprotic TFSI−-based ionic liquids as a function of temperature. The investigation is performed by Raman spectroscopy in the spectral ranges 240-380 cm−1 and 715-765 cm−1, where the interference from bands due to the cations is negligible. The contribution from each TFSI− conformation, i.e. the cisoid (C1) and the transoid (C2), is quantified in order to estimate the enthalpy of conformational change, ΔH, which is found to be in the range 3.4–7.3 kJ/mol in the liquid state. Conformational information is for the first time determined from the 740 cm−1 band, which previously mainly has been used as an indicator of ion-ion interactions. The similarity in ΔH values obtained from the two spectral ranges demonstrates the validity of using also the 740 cm−1 band for the quantification of the TFSI conformational evolution.
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| 5. |
- Martinelli, Anna, 1978, et al.
(författare)
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Phase behavior and ionic conductivity in LiTFSI doped ionic liquids of the pyrrolidinium cation and TFSI anion
- 2009
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 113:32, s. 11247-11251
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Tidskriftsartikel (refereegranskat)abstract
- The phase behavior and the ionic conductivity of ionic liquids (ILs) of the N-alkyl-N-alkylpyrrolidinium (PYR xy ) cation and the bis(trifluoromethanesulfonyl)imide (TFSI) anion are investigated upon addition of LiTFSI salt. We compare the case of two new ILs of the PYR 2y cation (where 2 is ethyl and y is butyl or propyl) with that of the PYR 14 (where 1 is methyl and 4 is butyl). We find that the addition of LiTFSI increases the glass transition temperature, decreases the melting temperature and the heat of fusion and, in the ILs of the PYR 2y family, suppresses crystallization. In the solid state, significant ionic conductivities are found, being as high as 10 -5 Scm -1 , strongly increasing with Li + concentration. The opposite trend is found in the liquid state, where the conductivity is on the order of 10 -3 -10 -2 Scm -1 at room temperature. A T g -scaled Arrhenius plot shows that the liquid-state ionic conductivity in these systems is mainly governed by viscosity and that the fragility of the liquids is slightly influenced by the structural modifications on the cation. © 2009 American Chemical Society.
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| 6. |
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| 7. |
- Martinelli, Anna, 1978, et al.
(författare)
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Structural analysis of PVA-based proton conducting membranes
- 2006
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 177:26-32, s. 2431-2435
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Tidskriftsartikel (refereegranskat)abstract
- We have synthesized and characterized a new family of proton conducting membranes based on cross-linked poly(vinyl alcohol), PVA, and functionalized silica filler. Glutaraldehyde, GLA, was used as the cross-linking agent in order to improve chemical and thermal stabilities. The functionalization of the silica particles is such that terminal -SO 3 H groups are formed during membrane preparation, thus possibly providing additional mobile protons. We find that the crystallinity of the PVA-based membranes is enhanced by the presence of the functionalized silica particles, whereas it is reduced by means of cross-linking. The thermal stability of the ternary system PVA:GLA:silica is improved due to the additive contribution of GLA and silica. The conductivity of membranes swelled in a sulfuric acid solution was found to be of the order of 10 - 1 S cm - 1 . © 2006 Elsevier B.V. All rights reserved.
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| 8. |
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| 9. |
- Pitawala, Jagath, 1976, et al.
(författare)
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Coordination and interactions in a Li-salt doped ionic liquid
- 2015
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Ingår i: Journal of Non-Crystalline Solids. - : Elsevier BV. - 0022-3093. ; 407, s. 318-323
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Tidskriftsartikel (refereegranskat)abstract
- We report on the coordination and interactions in the LiTFSI doped ionic liquid PyR14TFSI over a large concentration range, 0.01 2. The number decreases with increasing salt concentration and the interaction between the Li-ion and the TFSI anions is rather weak in this concentration range. At intermediate concentrations, 0.1 0.2, N-TFSI/Li decreases further indicating the transition to more complex structures with Li-ions bridging TFSI anions. We also show that the evolution of the microscopic structure as a function of Li-salt concentration is mirrored in the behaviour of macroscopic properties such as the ionic conductivity and the glass transition temperature, which also show a crossover in the same concentration range.
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| 10. |
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