Structure of protic (HCnImNTf2, n=0–12) and aprotic (C1CnImNTf2, n=1–12) imidazolium ionic liquids: A vibrational spectroscopic study

Moschovi, Anastasia Maria; Dracopoulos, Vassilios

doi:10.1016/j.molliq.2015.06.035

Cited by 20 publications

(20 citation statements)

References 55 publications

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“…Thus, the evolution of the RTIL-air interface structure as the main interactions change gradually from mixed Coulomb-vdW to vdW dominance by varying the chain length, and that only, has not been hitherto determined by high-resolution X-ray methods for even a single long homologous RTIL series. Related issues were, however, addressed by simulations (10)(11)(12), and macroscopic (9,25,26) and compositional (27)(28)(29)(30)(31) methods. Thus, a quantitative determination of the structure's characteristics (layering periodicity and decay length) for a broad n range in a single RTIL series, as done here, should also provide an important yardstick for testing theoretical and simulation studies.…”

Section: Physicsmentioning

confidence: 99%

“…These interactions were shown in simulations, (4,5) and recently experimentally (2,3,6), to lead to the self-assembly of local nanostructure within the bulk, previously considered to be a homogeneous, locally isotropic, and unstructured simple liquid. While segregating the charged from the apolar moieties, the nanostructuring nevertheless leaves the corresponding bulk correlations liquidlike (LL) and short-ranged (2,3,(6)(7)(8)(9). RTILs are, therefore, an intriguing borderline case between molecularly ordered longrange-correlated solids and nanoscale-uniform, isotropic, shortrange-ordered, simple liquids.…”

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confidence: 99%

“…Their study impacts therefore not only RTILs but liquids in general. RTILs' bulk has been extensively studied by wide-angle X-ray scattering and small-angle X-ray scattering (SAXS) (2,3,7,8), which probe directly the bulk's molecular-scale structure, by other related measurements (7)(8)(9), and by simulations (10)(11)(12). All support strongly the existence of segregated domains of charged headgroups and apolar alkyl chains, organized, on a mesoscopic scale, as bilayers, clusters, hydrogen-bound networks, micelles, bicontinuous phases, etc.…”

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confidence: 99%

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Surface structure evolution in a homologous series of ionic liquids

Haddad

Pontoni

Murphy

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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Interfaces of room temperature ionic liquids (RTILs) are important for both applications and basic science and are therefore intensely studied. However, the evolution of their interface structure with the cation's alkyl chain length [Formula: see text] from Coulomb to van der Waals interaction domination has not yet been studied for even a single broad homologous RTIL series. We present here such a study of the liquid-air interface for [Formula: see text], using angstrom-resolution X-ray methods. For [Formula: see text], a typical "simple liquid" monotonic surface-normal electron density profile [Formula: see text] is obtained, like those of water and organic solvents. For [Formula: see text], increasingly more pronounced nanoscale self-segregation of the molecules' charged moieties and apolar chains yields surface layering with alternating regions of headgroups and chains. The layering decays into the bulk over a few, to a few tens, of nanometers. The layering periods and decay lengths, their linear [Formula: see text] dependence, and slopes are discussed within two models, one with partial-chain interdigitation and the other with liquid-like chains. No surface-parallel long-range order is found within the surface layer. For [Formula: see text], a different surface phase is observed above melting. Our results also impact general liquid-phase issues like supramolecular self-aggregation and bulk-surface structure relations.

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Section: Physicsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Surface structure evolution in a homologous series of ionic liquids

Haddad

Pontoni

Murphy

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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“…In the spectra of IL and INF, the 1400 to 880 cm −1 wavenumber region ( Figure 7A) contains the signature of cis and trans conformations of the triflate (TFSI) ions. 49 The overwhelming existence of the vibration bands at 1138 and 1359 cm −1 in the spectrum of [Deim][TFSI] IL indicates the favorable existence of trans-TFSI conformation within it. 36 However, in the INF spectrum, the intensity Sample of those bands is considerably suppressed, and the bands corresponding to the cis-TFSI conformation (1143 and 1333 cm −1 )evolve.…”

Section: Ion Association: Ft-ir Analysismentioning

confidence: 99%

Ionanofluid plasticized electrolyte with improved electrical and electrochemical properties for high‐performance lithium polymer battery

2020

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Herein, the electrochemical characteristics of Li/LiFePO 4 battery, comprising a new class of poly (ethylene oxide) (PEO) hosted polymer electrolytes, are reported. The electrolytes were prepared using lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) dopant salt and imidazolium ionic liquid-based nanofluid (ionanofluid) as the plasticizer. Morphological, thermophysical, electrical, and electrochemical properties of these newly developed electrolytes were studied. Using FT-IR spectroscopy, the interactions between dopant salt plasticizers and the host polymer, within the electrolytes, were evaluated. The optimized 30 wt% ionanofluid plasticized electrolyte exhibits a room temperature ionic conductivity of 6.33 × 10 −3 S cm −1 , wide electrochemical voltage window (4.94 V vs Li/Li +) along with a moderately high value of lithium-ion transference number (0.47). The values are substantially higher than that of similar wt% IL plasticized electrolyte (7.85 × 10 −4 S cm −1 , 4.44 V vs Li/Li + and 0.28, respectively). Finally, the Li/LiFePO 4 battery, comprising optimized 30 wt% ionanofluid plasticized electrolyte, delivers 156 mAh g −1 discharge capacity at 0.1 C rate and able to retain its 92% value after 50 cycles. Such a superior battery performance as compared to the IL plasticized electrolyte cell (137 mAh g −1 and 84% after 50 cycles at the same current rate) would endow this ionanofluid a very promising plasticizer to develop electrolytes for next-generation lithium polymer battery.

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“…Since peak III reflects these correlations, the corresponding d III decreases with increasing n. Concurrently, the growing molecular volume increases the cation-cation and anion-anion spacings d II . There is also experimental evidence for an increase in the charge delocalization in the imidazolium ring with increasing chain length, [73] which should also contribute to the increase in d II . The opposite trends in d II and d III stand out clearly in Figure 6 for n ¼ 1 À 3 where no, or very weak, layering occurs.…”

Section: Structural Implicationsmentioning

confidence: 99%

Nanoscale Structure in Short‐Chain Ionic Liquids

2020

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The temperature (T) and cationic chain length (n) evolution of the nanoscale structure of the sub‐layering‐threshold members of a model family of room temperature ionic liquids (RTILs) is investigated by x‐ray scattering. The measured curves are computer‐resolved into individual Teubner‐Strey‐like lineshapes. The polar‐apolar layering is found to start at n=3 . Opposite n‐trends are found at n≤3 for the spacings and correlation lengths associated with the diffraction patterns’ two main peaks, and assigned to a shift of balance between the two main interactions, Coulomb and van der Waals, and to increasing packing constraints due to the addition of methylenes. The spacings’ thermal expansion coefficients are found to deviate from the macroscopically‐measured values, and to anomalously decrease with increasing temperature. Finally, the reduced temperature scale, t=(T-Tm)/Tm , (Tm= melting temperature), is demonstrated to render the observed trends significantly more systematic than those on a conventional T scale.

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Structure of protic (HCnImNTf2, n=0–12) and aprotic (C1CnImNTf2, n=1–12) imidazolium ionic liquids: A vibrational spectroscopic study

Cited by 20 publications

References 55 publications

Surface structure evolution in a homologous series of ionic liquids

Surface structure evolution in a homologous series of ionic liquids

Ionanofluid plasticized electrolyte with improved electrical and electrochemical properties for high‐performance lithium polymer battery

Nanoscale Structure in Short‐Chain Ionic Liquids

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