Thermal Analysis and Heat Capacities of 1-Alkyl-3-methylimidazolium Ionic Liquids with NTf2–, TFO–, and DCA– Anions

Gómez, Elena; Calvar, Noélia; Domínguez, Ángeles; Macedo, Eugénia A.

doi:10.1021/ie3012193

Cited by 65 publications

(66 citation statements)

References 36 publications

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“…Since crystallization is usually a very slow process in ILs, the dynamic nature of this experiment does not allow a full crystallization of the dense ionic material to take place in the cooling part of the cycle. This cold crystallization after a Tg is typically observed in glass-forming liquids when cooled rapidly enough to prevent crystallization, as it has previously been reported for some based on pyrrolidinium-and methylimidazolium-based ILs [10][11][12][13]. The glass transition is not directly observed here, since EAN's glass transition temperature (previously reported to be -91 ºC [6]) lies clearly below our lowest studied temperature.…”

Section: Chemicalsupporting

confidence: 69%

Thermal characterization of ethylammonium nitrate

Salgado

Teijeira

Parajó

et al. 2016

Proceedings of the 20th International Electronic Conference on Synthetic Organic Chemistry

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Thermal analysis techniques (DSC and TG) were used to characterize the melting and crystallization temperatures as well as the thermal stability of the ionic liquid ethylammonium nitrate. A detailed analysis of the solid-liquid transition is reported monitoring cooling -heating cycles by means of differential scanning calorimetry (DSC) and thermogravimetric balance, in the interval extending from -75 ºC to 100 ºC.The observed melting and solidification temperatures are in good agreement with previously reported ones in electrical conductivity analysis, and a novel cold crystallization at -40 ºC. The thermal analysis confirms the rich phase behaviour of a good glass-former, with a cold crystallization upon heating and a quite large supercooled region (-28, 17 ) ºC. Moreover, a fairly good thermal stability was detected by means of the thermogravimetric analysis up to 140-160 ºC, although the onset temperatures both in air and nitrogen atmospheres were found to lie well above this value.

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Section: Chemicalsupporting

confidence: 69%

Thermal characterization of ethylammonium nitrate

Salgado

Teijeira

Parajó

et al. 2016

Proceedings of the 20th International Electronic Conference on Synthetic Organic Chemistry

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“…So-called cold crystallization (when a low-temperature metastable state turns into a stable crystalline state, which only happens during heating) is highly dependent on the heating rate [41,42]. Such effects have also been described previously for pyrrolidinium [43], imidazolium [41], and pyridinium [13] ILs, and for binary IL mixtures [44].…”

Section: [Ch][lac]supporting

confidence: 61%

“…These were interpreted as solid-solid crystallization effects, where glass crystallizes into a solid and later melts at a higher temperature [28,40]. The presence of several exothermic transitions indicates the existence of different crystal structures at different temperatures [41]. So-called cold crystallization (when a Exothermic devitrification effects were often detected in the melting curves of the DSC thermograms (a typical example is presented in the Supplementary Materials).…”

Section: [Ch][lac]mentioning

confidence: 99%

“…These were interpreted as solid-solid crystallization effects, where glass crystallizes into a solid and later melts at a higher temperature [28,40]. The presence of several exothermic transitions indicates the existence of different crystal structures at different temperatures [41]. So-called cold crystallization (when a low-temperature metastable state turns into a stable crystalline state, which only happens during heating) is highly dependent on the heating rate [41,42].…”

Section: [Ch][lac]mentioning

confidence: 99%

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Influence of Carboxylate Anions on Phase Behavior of Choline Ionic Liquid Mixtures

et al. 2020

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Mixing ionic liquids is a suitable strategy to tailor properties, e.g., to reduce melting points. The present study aims to widen the application range of low-toxic choline-based ionic liquids by studying eight binary phase diagrams of six different choline carboxylates. Five of them show eutectic points with melting points dropping by 13 to 45 • C. The eutectic mixtures of choline acetate and choline 2-methylbutarate were found to melt at 45 • C, which represents a remarkable melting point depression compared to the pure compounds with melting points of 81 (choline acetate) and 90 • C (choline 2-methylbutarate), respectively. Besides melting points, the thermal stabilities of the choline salt mixtures were investigated to define the thermal operation range for potential practical applications of these mixtures. Typical decomposition temperatures were found between 165 and 207 • C, with choline lactate exhibiting the highest thermal stability.Advantages of DESs compared to pure ILs include easy preparation and therefore low production costs, increased biocompatibility in case of certain components, and bigger variety for customization concerning acidity, hydrophobicity, or polarity. DES systems have demonstrated their practical use in several applications, such as interfacial polymerizations [7], electrochemistry [8], and organic reactions [9].So far, the published research describing IL mixtures has mainly focused on imidazolium [10,11], pyrrolidinium [12], and pyridinium [13] ILs. In these works, significant melting point suppression effects were found for the respective eutectic mixtures. However, imidazolium, pyrrolidinium, and pyridinium ILs and their mixtures face some limitations when it comes to large-scale applications in contact with microorganisms or living matter [14]. Challenges include toxicity aspects and the cost for the organic cation synthesis. This is why a more detailed investigation of choline salts is highly interesting. Based on the available literature, choline salts are characterized by their low toxicity for different cell-lines [15,16], bacteria [17], and other organisms [18]. Moreover, choline salts are industrially available on a large scale.The most widely studied choline salt used in eutectic mixtures is choline chloride [19][20][21][22][23][24][25][26]. One of the first reported DESs was a mixture of choline chloride (liquefaction temperature 302 • C), and urea (melting point 134 • C) that resulted in a 2:1 molar mixture with a remarkable melting point suppression to 12 • C [4]. The typical strategy was to combine choline ILs with molecular compounds such as carboxylic acids, alcohols, and urea derivates [27], and such choline-based DESs have been used in various applications, e.g., as drug solubilization vehicles [28][29][30]. Note, however, that by mixing a choline IL with molecular substances, some of the very attractive IL properties, e.g., non-volatility, non-flammability, and high ionic conductivity can get lost to a large extent. This is why the mixing of two choline ILs is ...

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“…This behavior has previously been observed in many other ionic liquids such as Pyr 14 TFSI. [47][48][49][50][51] By contrast, C 2 HImTfO easily crystalizes upon cooling (see Fig.SI-6) and does not exhibit a glass transition nor a cold crystallization on heating. Its melting is detected at ∼27 • C.…”

Section: Phase Behaviormentioning

confidence: 99%

Effect of Water on the Local Structure and Phase Behavior of Imidazolium-Based Protic Ionic Liquids

Yaghini¹,

Pitawala

Matic³

et al. 2015

J. Phys. Chem. B

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We report on the effect of water on local structure and phase behavior of two protic ionic liquids, C2HImTFSI and C2HImTfO. Raman and infrared spectroscopy are employed to investigate the local coordination state. We find that water interacts weakly with TFSI(-) while more specifically with TfO(-) through the -SO3 group. Additionally, we observe that upon addition of water the -NH stretching frequency does not change in C2HImTFSI, while it red-shifts in C2HImTfO, indicative of different hydrogen bonding configurations. Supported by the appearance of some additional features in the 800-1000 cm(-1) frequency range where ring out-of-plane bending (γ) modes are found, we hypothesize that in C2HImTFSI water interacts only with the cation coordinating to the ring C(2)H and the N(3)H sites, while it interacts with both cation and anion in C2HImTfO forming hydrogen bonds that involve the cationic N-H site as well as the anionic -SO3 group. These different local structures also reflect in the phase behavior investigated by DSC, which reveals a more homogeneous solution when water is added to C2HImTfO, as compared to H2O/C2HImTFSI mixtures. Finally we report that the addition of water also significantly affects both Tm and Tg.

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Thermal Analysis and Heat Capacities of 1-Alkyl-3-methylimidazolium Ionic Liquids with NTf₂^–, TFO^–, and DCA^– Anions

Cited by 65 publications

References 36 publications

<strong>Thermal characterization of ethylammonium nitrate </strong>

<strong>Thermal characterization of ethylammonium nitrate </strong>

Influence of Carboxylate Anions on Phase Behavior of Choline Ionic Liquid Mixtures

Effect of Water on the Local Structure and Phase Behavior of Imidazolium-Based Protic Ionic Liquids

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