Ordering and Phase Transitions in Ionic Liquid‐Crystalline Films

Sobota, Marek; Wang, Xinjiao; Fekete, Melinda; Happel, Markus; Meyer, Karsten; Wasserscheid, Peter; Laurin, Mathias; Libuda, Jörg

doi:10.1002/cphc.201000144

Cited by 21 publications

(33 citation statements)

References 53 publications

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“…Therefore silica‐100 was chosen for our studies. In a previous publication, we have also shown that infrared spectroscopy was a suitable investigation method to follow the phase transitions of ILC substances 33. In this former paper, we were able to monitor the phase transitions of [C 12 C 12 Im][BF 4 ] spin‐coated on a metal surface by IRAS.…”

Section: Resultsmentioning

confidence: 90%

Surface‐Functionalized Ionic Liquid Crystal–Supported Ionic Liquid Phase Materials: Ionic Liquid Crystals in Mesopores

et al. 2011

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The influence of confinement on the ionic liquid crystal (ILC) [C(18)C(1)Im][OTf] is studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The ILC studied is supported on Si-based powders and glasses with pore sizes ranging from 11 to 50 nm. The temperature of the solid-to-liquid-crystalline phase transition seems mostly unaffected by the confinement, whereas the temperature of the liquid-crystalline-to-liquid phase transition is depressed for smaller pore sizes. A contact layer with a thickness in the order of 2 nm is identified. The contact layer exhibits a phase transition at a temperature 30 K lower than the solid-to-liquid-crystalline phase transition observed for the neat ILC. For applications within the "supported ionic liquid phase (SILP)" concept, the experiments show that in pores of diameter 50 nm a pore filling of α>0.4 is sufficient to reproduce the phase transitions of the neat ILC.

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Section: Resultsmentioning

confidence: 90%

Surface‐Functionalized Ionic Liquid Crystal–Supported Ionic Liquid Phase Materials: Ionic Liquid Crystals in Mesopores

et al. 2011

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“…Recently, we have shown how the desired structural information may be obtained in-situ from surface vibrational spectroscopy. [ 52 ] The corresponding experiment is summarized in Figure 7 . As a test system we have chosen 1,3-didodecylimidazolium tetrafl uoroborate [C 12 4 ] has been shown to undergo a transition to a smectic phase at approximately 430 K. [ 94 ] The degree of molecular ordering is followed by temperature-dependent IRAS (see Figure 7 a).…”

Section: Adv Mater 2011 23 2571-2587mentioning

confidence: 99%

“…An assignment of most peaks is straightforward, based on a comparison with previous work on similar ILs [ 99 ] and we refer to the original publication for further discussion. [ 52 ] Focussing on the liquid-liquid crystalline (LC) phase transformation, the latter is refl ected by a subtle spectral change occurring around 344 K (see Figure 7 a). Note that the more drastic change below 318 K is due to the LC-solid transition.…”

Section: Adv Mater 2011 23 2571-2587mentioning

confidence: 99%

“…[ 54 ] It should be kept in mind, however, that most surface science studies on IL interfaces have been performed on ex-situ prepared fi lms so far. In spite of the novelty of the fi eld, a broad spectrum of experimental methods have already been applied to IL fi lms, among which are X-ray photoelectron spectroscopy (XPS), [ 32-39 , 44 , 46-50 , 56 , 57 , 70 ] ultraviolet photoelectron spectroscopy (UPS), [ 33 , 35 , 40-42 , 70 ] infrared refl ection absorption spectroscopy (IRAS), [52][53][54][55] inverse photoelectron spectroscopy (IPES), [ 41 , 42 , 70 ] near edge X-ray absorption fi ne structure (NEXAFS), [ 41 ] metastable ion photoelectron spectroscopy (MIES), [33][34][35] direct recoil spectroscopy (DRS), [ 30 , 31 ] high-resolution electron energy loss spectroscopy (HREELS), [ 34 ] low energy ion scattering (LEIS), [ 32 ] time-of-fl ight secondary ion mass spectrometry (TOF-SIMS), [ 37 ] soft X-ray emission spectroscopy (SXES), [ 70 ] and Rutherford backscattering spectroscopy (RBS). [ 71 ] The number of studies is yet rather limited, however.…”

Section: Progress Reportmentioning

confidence: 99%

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Surface Science and Model Catalysis with Ionic Liquid‐Modified Materials

et al. 2011

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Materials making use of thin ionic liquid (IL) films as support-modifying functional layer open up a variety of new possibilities in heterogeneous catalysis, which range from the tailoring of gas-surface interactions to the immobilization of molecularly defined reactive sites. The present report reviews recent progress towards an understanding of "supported ionic liquid phase (SILP)" and "solid catalysts with ionic liquid layer (SCILL)" materials at the microscopic level, using a surface science and model catalysis type of approach. Thin film IL systems can be prepared not only ex-situ, but also in-situ under ultrahigh vacuum (UHV) conditions using atomically well-defined surfaces as substrates, for example by physical vapor deposition (PVD). Due to their low vapor pressure, these systems can be studied in UHV using the full spectrum of surface science techniques. We discuss general strategies and considerations of this approach and exemplify the information available from complementary methods, specifically photoelectron spectroscopy and surface vibrational spectroscopy.

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“…Differential scanning calorimetry (DSC) measurements of [C 18 C 1 Im][TfO] (see Figure S2 in the Supporting Information) show a first transition from the crystalline to the liquid-crystalline smectic A phase at 340.8 K, and a second from the smectic A to the isotropic phase at 380.1 K; these values are in good agreement with the literature. [17,18] It is interesting to study whether this is also reflected in the surface composition of the IL. [17,18] It is interesting to study whether this is also reflected in the surface composition of the IL.…”

Section: Im][tfo] [C 8 C 1 Im][tfo] and [C 18 C 1 Im][tfo]mentioning

confidence: 99%

Temperature‐Dependent Surface‐Enrichment Effects of Imidazolium‐Based Ionic Liquids

et al. 2013

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We present the first systematic study of the influence of temperature on the degree of surface enrichment of 1-alkyl-3-methylimidazolium-based ionic liquids (ILs). Using angle-resolved X-ray photoelectron spectroscopy, we demonstrate that the degree of surface enrichment strongly decreases with increasing temperature for all the studied ILs. For ILs with the same cation, but different anions, [C8 C1 Im]Br, [C8 C1 Im][TfO] and [C8 C1 Im][Tf2 N], no significant differences of the temperature-induced partial loss of surface enrichment are found. Measurements for [C4 C1 Im][TfO], [C8 C1 Im][TfO] and [C18 C1 Im][TfO] indicate a small effect of the chain length. For [C18 C1 Im][TfO], a continuous decrease of alkyl surface enrichment is found with increasing temperature, with no abrupt changes at the phase-transition temperature from the smectic A to the isotropic phase, indicating that the surface enrichment is not affected by this phase transition.

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Ordering and Phase Transitions in Ionic Liquid‐Crystalline Films

Cited by 21 publications

References 53 publications

Surface‐Functionalized Ionic Liquid Crystal–Supported Ionic Liquid Phase Materials: Ionic Liquid Crystals in Mesopores

Surface‐Functionalized Ionic Liquid Crystal–Supported Ionic Liquid Phase Materials: Ionic Liquid Crystals in Mesopores

Surface Science and Model Catalysis with Ionic Liquid‐Modified Materials

Temperature‐Dependent Surface‐Enrichment Effects of Imidazolium‐Based Ionic Liquids

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