Imidazolium camphorsulfonamides: Chiral catanionic liquid crystals with tunable thermal properties

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Imidazolium camphorsulfonamides: Chiral catanionic liquid crystalswith tunable thermal properties

Eva Rettenmeier a, Alexey Tokarev a, Christophe Blanc b, Philippe Dieudonné b, Yannick Guari c,Peter Hesemann a,⇑a Institut Charles Gerhardt de Montpellier, UMR 5253 CNRS/UM2/ENSCM/UM1, Equipe AM2N, Ecole Nationale Supérieure de Chimie, 8 rue de l’Ecole Normale,34296 Montpellier Cedex 05, Franceb Laboratoire Charles Coulomb UMR 5221 UM2/CNRS, Université Montpellier 2, Place Eugene Bataillon, 34296 Montpellier Cedex 05, Francec Institut Charles Gerhardt de Montpellier, UMR 5253 CNRS/UM2/ENSCM/UM1, Equipe CMOS, Université Montpellier 2, Place Eugene Bataillon, 34296 Montpellier Cedex 05, France

a r t i c l e i n f o

Article history:Received 22 November 2010Accepted 15 January 2011Available online 22 January 2011

Keywords:Chiral ionic liquidsLiquid crystalsCatanionic surfactantsCamphorsulfonamides

a b s t r a c t

We report the synthesis of novel chiral catanionic liquid crystals bearing camphorsulfonamide substruc-tures. The phase behaviour of these long-chain substituted imidazolium sulphates and sulfonates wasinvestigated using X-ray diffraction (XRD), polarizing optical microscopy (POM) and differential scanningcalorimetry (DSC). We observed that the phase behaviour clearly depends on the substitution of both cat-ion and anion. The chiral camphorsulfonamide substructures have an unfavourable influence on the for-mation of liquid crystalline (LC-) phases. Contrary to N,N0-di-alkyl-imidazolium salts, the formation of LCphases was only observed when both cation and anion are substituted with long alkyl chains (C12 or C16).Furthermore, the phase transition temperatures depend on the chain length of the alkyl groups, as higherphase transition temperatures were observed for compounds bearing longer alkyl chains. However, nomacroscopic evidence for the formation of chiral mesophases was obtained.

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1. Introduction

By definition, ionic liquids (ILs) are organic salts with meltingpoints below 100 �C, but sometimes as low as �96 �C, of which1,3-di-alkyl-imidazolium derivatives have been the most exten-sively studied. ILs display very peculiar properties due to theirpurely ionic character such as high thermal stability, negligible va-pour pressure, high ionic conductivity and high polarity. As a con-sequence, ILs attracted tremendous attention in the fields ofcatalysis [1], electrochemistry [2], separation processes [3] andmaterials’ synthesis [4].

The phase behaviour of ionic liquids is widely studied. Imidazo-lium derived ionic liquids form extended hydrogen bonded net-works in the liquid state [5] and are therefore highly structuredsolvents [6,7]. Structural modification on either the cation [8] orthe anion [9] can lead to increases of the structural anisotropy ofthese ionic compounds and allow in fine the formation of liquidcrystal phases [10,11] when dodecyl- or longer alkyl substituentsare present. Thus, they exhibit interesting potential applicationsas ion conductive materials [12], organized reaction media to mod-ulate the selectivity of organic reactions [13] and as templating[14] and stabilizing agents [15] in materials science.

On the other side, chiral ionic liquids (CILs) attracted high inter-est and have recently been reviewed [16,17]. The first example of achiral ionic liquid was reported in 1997 by Horwarth et al., who de-scribed the synthesis of the C2 symmetric N,N0-bis[(2S)-2-methyl-butyl]imidazolium bromide [18]. Since this time, the number ofchiral ionic liquids is rapidly growing and a large variety of CILsis available comprising systems with either chiral cations, chiralanions or bearing both chiral cationic and anionic species. Thesecompounds found applications [19] in catalysis and synthesis[20–22], in the field of molecular recognition [23], but also as chiralshift agents in NMR spectroscopy [24]. In the field of CILs, the cam-phor substructure was used to introduce chirality both on the an-ionic and the cationic part of ILs [25–29].

Following our recent work on functional [30] and chiral ionicliquids [31] and ionic liquid crystals [15,32], we focused here onthe synthesis of new chiral ionic liquid crystals bearing camphor-sulfonamide substructures. We already reported ionic liquids bear-ing chiral camphorsulfonamide substructures which appeared asrecyclable chiral auxiliaries in asymmetric catalysis [33]. We alsostudied the immobilization of these chiral ionic groups withinmesoporous nanostructured silica via template directed hydroly-sis-polycondensation procedures [34]. Here, we focused on thesynthesis and the determination of the phase behaviour of bothlong-chain substituted imidazolium halides bearing camphorsulf-onamide substructures and of catanionic surfactants constituted

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⇑ Corresponding author. Fax: +33 4 67 14 43 53.E-mail address: [email protected] (P. Hesemann).

Journal of Colloid and Interface Science 356 (2011) 639–646

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of cationic imidazolium camphorsulfonamide cations and long-chain substituted alkyl sulphate or sulfonate anions such as dode-cylsulphate or hexadecylsulfonate (Scheme 1). Catanionic surfac-tants attracted considerable interest due to their very particularphase behaviour [35–41] and found some applications as ionictemplates in the synthesis of nanostructured silica [42] and hollowsilica vesicles [43–45]. In this paper, we describe the synthesis ofionic liquid crystals from long-chain substituted imidazolium saltsbearing chiral camphorsulfonamide substructures. We addressedalso the formation of chiral mesophases due to the presence ofthe chiral camphorsulfonamide groups. In fact, examples of chiralionic liquid crystals (ILCs) are scarce, and among the few examplesreported in the literature [46–50], only one example reported theformation of chiral mesophases [51].

2. Materials and methods

2.1. General details

The imidazole functionalized camphorsulfonamide was pre-pared as previously reported [33]. Methyl iodide, 1-bromododecane,1-iodohexadecane were purchased from Aldrich (www.sigmaald-rich.com), sodium dodecylsulphate and sodium hexadecylsulfonatewere purchased from ABCR (www.abcr.de).

1H and 13C spectra in solution were recorded on Bruker AC 250or Bruker Avance 400 spectrometers at room temperature. Deuter-ated chloroform was used as solvent for liquid NMR experimentsand chemical shifts are reported as d values in parts per million rel-ative to tetramethylsilane. IR samples were prepared as KBr pellets.FT-IR spectra were measured on a Perkin–Elmer 1000 FT-IR spec-trometer. MS-ESI were measured on Water Q-Tof mass spectrom-eter. Optical rotations were measured on a Perkin-Elmerpolarimeter 241. The melting points, clearing points, and glass-transition temperatures were determined by differential scanningcalorimetry (NETZSCH PSC 204 F1 Phoenix equipped with dinitro-gen cryostatic cooling, 5–15 mg samples, 2 K min�1 heating andcooling rates), calibrated using an indium primary standard. Opti-cal characterization of the compounds and the detection of meso-phases were performed with a polarizing microscope (Leitz 12 POLS) equipped with a 1024 pixel � 768 pixel Sony CCD camera and anInstec hot stage regulated at 0.1 �C. Powder samples were depos-ited between slides and cover slips and inserted into the hot stageat room temperature. The temperature was then slowly increased(typically 1 �C/min), and the phase transitions were detected fromthe texture changes observed between crossed polarizers. Once inthe isotropic phase, the temperature was decreased, and the phasetransitions under cooling were similarly detected. X-ray diffractionmeasurements on dried powders were carried out in 1.5-mm-diameter glass capillaries in a transmission configuration. A copperrotating anode X-ray source (functioning at 4 kW) with a multi-layer focusing Osmic monochromator giving high flux (108 pho-tons/s) and punctual collimation was employed. An image plate2D detector was used. X-ray diffractograms were obtained, givingthe scattering intensity as a function of the wave vector q.

2.2. Syntheses

2.2.1. Synthesis of the imidazolium salts 2, 3 and 41-Methyl-3-{3-[(1S,2S,4S)-(2-hydroxy-7,7-dimethyl-bicyclo-

[2.2.1]hept-1-ylmethyl)sulfamoyl]-propyl}-3H-imidazol-1-iumiodide 2: Methyl iodide (2.13 g, 0.94 mL, 15 mmol) was added toa solution of compound 1 (3.15 g, 9.2 mmol) in acetonitrile(50 mL). The mixture was stirred for 30 h at room temperature.After evaporation of the solvent, the product was purified bywashing with diethyl ether and finally dried under high vacuumat 40 �C overnight to give a highly viscous brownish oil. Yield:4.06 g, 92%. 1H NMR (CDCl3): d: 0.82 (s, 3H), 0.97 (s, 3H), 1.40(m, 1H), 1.74–2.10 (m, 4H), 2.15–2.32 (m, 4H), 2.91 (d,J = 14.9 Hz, 1H), 3.20 (m, 2H), 3.37 (d, J = 14.9 Hz, 1H), 4.00 (s,3H), 4.46 (t, J = 6.7 Hz, 2H), 6.26 (m, 1H), 7.41 (s, 1H), 7.63 (s,1H), 9.51 (s, 1H); 13C NMR (CDCl3): d = 19.4, 19.7, 25.3, 26.7,30.1, 36.9, 39.4, 42.3, 42.5, 46.8, 48.3, 48.6, 58.3, 122.6, 123.5,136.6, 214.9; FT-IR(KBr) mmax/cm�1 3468, 3153, 3101, 2961,1744, 1574, 1454, 1328, 1147, 1091. MS [TOF ESI+] calcd. forC17H28N3O3S (M)+ 354.1851, found 354.1855. ½a�2D5 = +16.7(c = 1.38, CH2Cl2).

1-Dodecyl-3-{3-[(1S,2S,4S)-(2-hydroxy-7,7-dimethyl-bicyclo-[2.2.1]hept-1-ylmethyl)sulfamoyl]-propyl}-3H-imidazol-1-iumbromide 3: 1-Bromododecane (2.4 g, 9.2 mmol) was added to solu-tion of compound 1 (3.15 g, 9.2 mmol) in acetonitrile (50 mL). Themixture was stirred for 30 h at 80 �C. After evaporation of thesolvent, the product was purified by washing with diethyl etherand finally dried under high vacuum at 40 �C overnight. Yield:5.31 g/98% of a colourless highly viscous oil. 1H NMR (CDCl3): d:0.80 (m, 6H), 0.97 (s, 3H), 1.07–1.42 (m, 17H), 1.77–2.07 (m, 8H),2.13–2.31 (m, 4H), 2.85 (d, J = 14.9 Hz, 1H), 3.22 (m, 2H), 3.36 (d,J = 14.9 Hz, 1H), 4.19 (‘t’, 2H), 4.51 (m, 2H), 6.94 (‘t’, 1H), 7.17, s,1H), 7.53 (s, 1H), 10.17 (s, 1H). 13C NMR (CDCl3): d = 14.2, 19.6,19.7, 22.5, 25.1, 26.2, 26.9, 28.9, 29.2, 29.3, 29.4, 29.5 (2C), 30.1,30.5, 31.8, 39.4, 42.5, 42.6, 46.9, 48.2, 48.3, 49.9, 58.3, 122.0,123.1, 136.6, 215.4. FT-IR(KBr) mmax/cm�1 3417, 3093, 2924,2854, 1746, 1565, 1455, 1325, 1150. MS [TOF ESI+] calcd. forC28H50N3O3S (M)+ 508.3573, found 508.3573. ½a�2D5 = +11.5(c = 0.435, CH2Cl2).

1-Hexadecyl-3-{3-[(1S,2S,4S)-(2-hydroxy-7,7-dimethyl-bicy-clo[2.2.1]hept-1-ylmethyl)sulfamoyl]-propyl}-3H-imidazol-1-iumiodide 4: This compound was synthesized similar to compound 3except using 1-iodohexadecane (3.27 g, 9.2 mmol) instead of1-bromododecane. Yield: 6.11/96% of a brownish oil which crystal-lized upon standing. 1H NMR (CDCl3): d: 0.80 (m, 6H), 0.98 (s, 3H),1.15–1.42 (m, 27H), 1.76–2.30 (m, 10H), 2.86 (d, J = 14.9 Hz, 1H),3.18 (m, 2H), 3.36 (d, J = 14.9 Hz, 1H), 4.19 (‘t’, 2H), 4.50 (m, 2H),7.31 (s, 1H), 7.49 (s, 1H), 7.77 (‘t’, 1H), 10.09 (s, 1H). 13C NMR(CDCl3): d = 13.9, 19.4, 19.6, 22.4, 25.0, 26.1, 26.8, 28.8, 29.1, 29.2,29.3, 29.4 (5C), 29.5, 29.9, 30.3, 31.7, 39.4, 42.4, 42.5, 46.9, 48.1,48.2, 49.8, 58.2, 121.7, 122.8, 136.5, 215.5. FT-IR(KBr) mmax/cm�1

3383, 2923, 2853, 1747, 1566, 1455, 1324, 1148. MS [TOF ESI+]calcd. for C32H58N3O3S (M)+ 564.4199, found 564.4196. ½a�2D5 =+16.0 (c = 1.01, CH2Cl2).

2.2.2. Anion exchange reactions: general procedureAn aqueous solution of sodium n-dodecyl sulphate or sodium-1

hexadecane sulfonate mixed with a solution containing an equi-molar amount of the imidazolium camphorsulfonamide halides2, 3 or 4 in CH2Cl2 (50 mL). The reaction mixtures were vigorouslystirred at room temperature for 30 min. After this time, the organicphase was separated and washed with water twice. The combinedorganic phases were dried over sodium sulphate. Evaporation ofthe solvent under reduced pressure yielded the corresponding imi-dazolium sulphates or -sulfonates 5–10 in quantitative yields. Thecompounds 5–10 were obtained as white or off-white solids.

NN NH

SO2 OH2n+1Cn H2m+1Cm (O)xSO3-

Hal-

or

Scheme 1. Chiral ionic liquid compounds studied in this work.

640 E. Rettenmeier et al. / Journal of Colloid and Interface Science 356 (2011) 639–646


Methyl-3-{3-[(1S,2S,4S)-(2-hydroxy-7,7-dimethyl-bicyclo[2.2.1]-hept-1-ylmethyl)sulfamoyl]-propyl}-3H-imidazol-1-ium dodecyl-sulphate 5: 1H NMR (CDCl3): d = 0.80 (m, 6H), 0.97 (s, 3H),1.10–1.33 (m, 18H), 1.37 (m, 1H), 1.57 (m, 2H), 1.73 (m, 1H),1.81–2.07 (m, 3H), 2.07–2.33 (m, 4H), 2.85 (d, J(HH) = 14.7 Hz,1H), 3.15 (m, 2H), 3.33 (d, J(HH) = 14.7 Hz, 1H) 3.92 (s, 3H), 3.95(t, J(HH) = 6.7 Hz, 2H), 4.34 (t, J(HH) = 6.7 Hz, 2H), 6.34 (t,J(HH) = 6.7H, 1H), 7.20 (s, 1H), 7.45 (s, 1H), 9.34 (s, 1H). 13C NMR(CDCl3): d = 14.1,19.6, 19.7, 22.6, 25.2, 25.9, 27.0, 29.3, 29.4, 29.5,29.6 (3C), 29.7, 30.3, 31.9, 36.3, 39.8, 42.6, 42.7, 47.0, 48.2, 48.3,58.4, 67.8, 122.8, 123.6, 137.3, 215.7. FT-IR(KBr) mmax/cm�1 3155,3100, 2924, 2854, 1747, 1577, 1329, 1249, 1150. MS [TOF ESI+]calcd. for C17H28N3O3S (M)+ 354.1851, found 354.1853. ½a�2D5 =+12.7 (c = 0.85, CH2Cl2).

Methyl-3-{3-[(1S,2S,4S)-(2-hydroxy-7,7-dimethyl-bicyclo[2.2.1]-hept-1-ylmethyl)sulfamoyl]-propyl}-3H-imidazol-1-ium hexade-cylsulfonate 6: 1H NMR (CDCl3): d = 0.80 (m, 6H), 0.98 (s, 3H),1.07–1.42 (m, 27H), 1.64–1.78 (m, 3H), 1.78–1.90 (m, 1H), 1.90–2.06 (m, 2H), 2.06–2.20 (m, 2H), 2.20–2.37 (m, 2H), 2.76 (m, 2H),2.86 (d, J(HH) = 14.7 Hz, 1H), 3.14 (m, 2H), 3.34 (d, J(HH) = 14.7,1H), 3.93 (s, 3H), 4.36 (t, J(HH) = 6.7 Hz, 2H), 6.93 (s, 1H), 7.33 (s,1H), 7.57 (s, 1H), 9.47 (s, 1H). 13C NMR (CDCl3): d = 14.1, 19.6, 19.7,22.6, 25.0, 25.3, 26.9, 29.0, 29.3, 29.4, 29.5, 29.6, 29.6, 29.7 (5C),30.3, 31.8, 36.3, 39.7, 42.5, 42.6, 46.9, 48.1, 48.2, 52.1, 58.3, 122.8,123.5, 137.6, 215.5. FT-IR(KBr) mmax/cm�1 3155, 3098, 2923, 2853,1746, 1570, 1326, 1249, 1149. MS [TOF ESI+] calcd. for C17H28N3O3S(M)+ 354.1851, found 354.1854. ½a�2D5 = +10.6 (c = 0.63, CH2Cl2).

1-Dodecyl-3-{3-[( 1S,2S,4S)-(2-hydroxy-7,7-dimethyl-bicyclo-[2.2.1]hept-1-ylmethyl)sulfamoyl]-propyl}-3H-imidazol-1-iumdodecylsulphate 7: 1H NMR (CDCl3): d: 0.85–0.88 (m, 9H, 3 � CH3),1.03 (s, 3H, CH3), 1.24–1.40 (m, 3H, CH + CH2; 20H, 10H2), 1.66 (p,2H, CH2) 1.76–1.94 (m, 4H, 2 � CH2), 1.96–2.12 (m, 2H), 2.2–2.4(m, 2H), 2.90 (d, 1H, J = 14.905 Hz), 3.2–3.32 (m, 2H), 3.4 (d, 1H,J = 14.905 Hz), 4.03 (t, 2H, J = 6.905 Hz), 4.21 (t, 2H, J = 7.452 Hz),4.45 (3H, CH + CH2), 6.42 (br s, 1H) 7.26 (s, 1H), 7.49 (s, 1H), 9.52(s, 1H). 13C NMR (CDCl3): d = 14.1, 19.6, 19.8, 22.7, 25.3, 25.9,26.3, 27.0, 29.0, 29.3, 29.4, 29.5, 29.6, 29.6, 29.7, 30.06, 31.9, 40.0,42.6, 42.7, 47.3, 48.3, 48.4, 50.1, 58.4, 68.0, 122.7, 123.5, 137.6,215.9. MS [TOF ES] calcd. for C28H50N3O3S (M)+ 508.3573, found508.3570; calcd. for C12H25O4S (M)� 265.1474, found 265.1477.FT-IR(KBr) mmax/cm�1 3152, 3100, 2907, 2851, 1738, 1567, 1469,1325, 1265, 1219, 1153, 1053, 794. Elemental analysis; calcd. C,62.06; H, 9.76; N, 5.43; found C, 61.77; H, 9.60; N 5.35.½a�2D5 = +11.1 (c = 1.0, CH2Cl2).

1-Dodecyl-3-{3-[( 1S,2S,4S)-(2-hydroxy-7,7-dimethyl-bicyclo-[2.2.1]hept-1-ylmethyl)sulfamoyl]-propyl}-3H-imidazol-1-iumhexadecylsulfonate 8: 1H NMR (CDCl3): d: 0.85–0.88 (m, 9H,3 � CH3), 1.03 (s, 3H, CH3), 1.24–1.40 (m, 3H, CH + CH2; 50H,25H2), 1.76–1.94 (m, 4H, 2 � CH2; p, 2H, CH2), 1.96–2.12 (m, 2H),2.2–2.4 (m, 2H), 2.81 (t, 2H, J = 8.084 Hz), 2.90 (d, 1H,J = 14.905 Hz), 3.2–3.32 (m, 2H), 3.4 (d, 1H, J = 14.905 Hz), 4.21 (t,2H, J = 7.579 Hz), 4.45 (3H, CH + CH2), 6.95 (br s, 1H), 7.26 (s,1H), 7.49 (s, 1H), 9.52 (s, 1H). 13C NMR (CDCl3): d = 14.1, 19.7,19.8, 22.7, 25.0, 25.3, 26.3, 27.0, 29.0, 29.3, 29.4, 29.5, 29.5, 29.6,29.7, 30.0, 30.2, 31.9, 39.9, 42.6, 42.7, 47.2, 48.1, 48.3, 50.0, 52.1,58.4, 122.4, 123.7, 137.3, 215.6. MS [TOF ES] calcd. for C28H50N3O3S(M)+ 508.3573, found 508.3578; calcd. for C16H33O3S (M)�

305.2150, found 305.2124. FT-IR(KBr) mmax/cm�1 3143, 3099,2916, 1731, 1567, 1469, 1328, 1152, 1100. Elemental analysis;calcd. C, 64.90; H, 10.27; N, 5.16; found C, 64.20; H, 10.37; N,4.98. ½a�2D5 = +7.4 (c = 1.0, CH2Cl2).

1-Hexadecyl-3-{3-[(1S,2S,4S)-(2-hydroxy-7,7-dimethyl-bicy-clo[2.2.1]hept-1-ylmethyl)sulfamoyl]-propyl}-3H-imidazol-1-iumdodecylsulphate 9: 1H NMR (CDCl3): d: 0.85–0.88 (m, 9H, 3 � CH3),1.03 (s, 3H, CH3), 1.24–1.40 (m, 3H, CH + CH2; 50H, 25H2), 1.66 (p,2H, CH2) 1.76–1.94 (m, 4H, 2 � CH2), 1.96–2.12 (m, 2H), 2.2–2.4

(m, 2H), 2.90 (d, 1H, J = 14.905 Hz), 3.2–3.32 (m, 2H), 3.4 (d, 1H,J = 14.905 Hz), 4.03 (t, 2H, J = 6.905 Hz), 4.21 (t, 2H, J = 7.452 Hz),4.45 (3H, CH + CH2), 6.40 (br s, 1H) 7.26 (s, 1H), 7.49 (s, 1H), 9.52(s, 1H). 13C NMR (CDCl3): d = 14.1, 19.6, 19.8, 22.7, 25.3, 25.9,26.3, 27.0, 29.0, 29.3, 29.4, 29.5, 29.6, 29.6, 29.7, 30.0, 31.9, 40.0,42.6, 42.7, 47.3, 48.3, 48.4, 50.1, 58.4, 68.0, 122.7, 123.9, 137.7,215.9. MS [TOF ES] calcd. for C32H58N3O3S (M)+ 564.4199, found564.4195; calcd. for C12H25O4S (M)- 265.1474, found 265.1454.FT-IR(KBr) mmax/cm�1 3145, 3100, 2921, 2850, 1736, 1568, 1467,1327, 1265, 1207, 1153, 1053, 794. Elemental analysis; calcd. C,63.65; H, 10.08; N, 5.06; found C, 63.57; H, 10.24; N, 5.11.½a�2D5 = +6.9 (c = 1.0, CH2Cl2).

1-Hexadecyl-3-{3-[(1S,2S,4S)-(2-hydroxy-7,7-dimethyl-bicy-clo[2.2.1]hept-1-ylmethyl)sulfamoyl]-propyl}-3H-imidazol-1-iumhexadecylsulfonate 10: 1H NMR (CDCl3): d : 0.85–0.88 (m, 9H,3 � CH3), 1.03 (s, 3H, CH3), 1.24–1.40 (m, 3H, CH + CH2; 58H,29H2), 1.76–1.94 (m, 4H, 2 � CH2; p, 2H, CH2), 1.96–2.12 (m, 2H),2.2–2.4 (m, 2H), 2.78 (t, 2H, J = 8.084 Hz), 2.90 (d, 1H,J = 14.905 Hz), 3.2–3.32 (m, 2H), 3.4 (d, 1H, J = 14.905 Hz), 4.21 (t,2H, J = 7.579 Hz), 4.45 (3H, CH + CH2), 6.95 (br s, 1H), 7.26 (s,1H), 7.49 (s, 1H), 9.52 (s, 1H). 13C NMR (CDCl3): d = 14.1, 19.7,19.8, 22.7, 25.0, 25.3, 26.3, 27.0, 29.0, 29.3, 29.4, 29.5, 29.5, 29.6,29.7, 30.0, 30.2, 31.9, 39.9, 42.6, 42.7, 47.2, 48.1, 48.3, 50.0, 52.1,58.4, 122.7, 123.6, 137.4, 215.6. MS [TOF ES] calcd. for C32H58N3O3S(M)+ 564.4199, found 564.4193; calcd. for C16H33O3S (M)�

305.2150, found 305.2166. FT-IR(KBr) mmax/cm�1 3151, 3104,2922, 2850, 1741, 1471, 1331, 1215, 1167, 1040. Elemental analy-sis; calcd. C, 66.24; H, 10.54; N, 4.83; found C, 65.81; H, 10.63; N,4.83. ½a�2D5 = +9.0 (c = 1.0, CH2Cl2).

3. Results and discussion

3.1. Synthesis of the imidazolium sulphates and -sulfonates

We studied the phase behaviour of ionic imidazolium saltsbearing chiral camphorsulfonamide substructures. The synthesisof such salts was achieved by alkylation of the imidazole function-alized camphorsulfonamide 1 which was synthesized from 3-ami-nopropyl imidazole and D-camphor-10-sulfonyl chloride accordingto Scheme 2.

This intermediate was alkylated with iodomethane, 1-bromo-dodecane or 1-bromohexadecane to yield the corresponding imi-dazolium salts 2–4. These compounds were subsequently usedfor anion metathesis with either sodium dodecylsulphate (SDS)or sodium hexadecylsulfonate (SHS) giving the compounds 5–10as shown in Scheme 3.

The characterization of the imidazolium dodecylsulphates 5, 7and 9 and the hexadecylsulfonates 6, 8 and 10 by NMR spectroscopyshowed that anionic and cationic species are present in equimolarratio in the product obtained after metathesis. Furthermore, ele-mental analysis gave results in good agreement with the expectedvalues and indicate that the sequences allowed to obtain analyticallypure long-chain substituted imidazolium sulphates and sulfonates.

3.2. Thermotropic phase behaviour of the imidazolium sulphates and -sulfonates

The phase behaviour of the obtained ionic compounds wasstudied by combined differential Scanning calorimetry (DSC),polarizing optical microscopy (POM) and X-ray diffraction (XRD)measurements.

3.2.1. Differential scanning calorimetry (DSC)At first, the properties of the long-chain substituted imidazoli-

um halides 3 and 4 were studied. The DSC thermograms revealed

E. Rettenmeier et al. / Journal of Colloid and Interface Science 356 (2011) 639–646 641


no crystallinity nor mesomorphicity. Glass transitions were ob-served at temperatures in the range between �10 �C and 0 �C.These results show that the chiral camphorsulfonamide grouphas strong influence on the phase behaviour of such ionic com-pounds, as related methyl-substituted imidazolium halides suchas 1-cetyl-3-methylimidazolium chloride show thermotropic li-quid crystalline behaviour [8,52]. Thus, the chiral organic cam-phorsulfonamide group strongly decreases the crystallinity in theionic liquid crystalline compounds 3 and 4 and leads to the forma-tion of non-crystalline, non-mesomorphic compounds.

The same tendency was observed for the methyl-substitutedimidazolium camphorsulfonamides with dodecylsulphates or hex-adecylsulfonates counterions 5 and 6. These compounds show verysimilar phase behaviour compared to the materials 3 and 4 withglass transitions below 0 �C. No crystallinity or mesomorphismwas observed with these compounds.

Contrarily to these results, the compounds 7–10 bearing C12 orC16 alkyl chains both on the cation and the anion show a differentphase behaviour. Fig. 1 displays the thermograms of compounds 8and 10. Compound 8 shows a thermogram with a characteristiclarge endothermic enthalpy at 30.7 �C indicating a Cr ? SmA tran-sition and the presence of a mesophase below the isotropic phasethat appears at 93.7 �C with a much weaker enthalpy. The sametransitions were found in the cooling cycle. We identified this

mesophase to be a smectic A by polarizing microscopy and X-raydiffraction (see below). The DSC traces of the compounds 7, 9and 10 show additional peaks of unidentified smectic ‘X’ phases.A similar phase behaviour has already been observed for othercatanionic liquid crystals [53], for example in the case of N-ethyl-N0-dodecylimidazolium dodecylsulfonate [54]. The imidazo-lium hexadecylsulfonate 10 shows a Cr ? SmA transition at55.7 �C and a LC ? I enthalpy at 123.4 �C. Additional intense phasetransitions were observed in the range from 50 to 70 �C which weattribute to the formation of unidentified metastable smectic ‘X’phases.

Compounds 7 and 9 show similar phase behaviour. These com-pounds form mesophases at temperatures of 20.8 and 37.2 �C andisotropic melts at 79.6 and 107.7 �C, respectively. The DSC thermo-grams of these two compounds also indicate the formation ofmetastable mesophases as observed in the heating cycle of thecompound 10 (see Supporting information), which is probablydue to crystallization of aggregated alkyl chain layers [54].

The chain length of the alkyl tails has direct influence on thephase transition temperatures of the ionic liquid crystals, both onthe Cr ? SmA transitions and on the SmA ? I transition. The low-est phase transition temperatures were observed for compound 7bearing dodecyl (C12) chains both on the cation and on the anion.The ‘mixed’ compounds 8 and 9 containing a C12 chain and a C16

NN

ClO2S O

NH2

NN NH

SO2 O

+

(1)

CH2Cl2, NEt3

r. t.NN N

H

SO2 O

NN NH

SO2 OH33C16

H25C12

C16H33I

C12H25Br

(3)

(4)

Δ

Δ

I-

Br-

NN NH

SO2 OH3C

(2)I-

Δ

CH3I

Scheme 2. Synthesis of the long-chain substituted imidazolium salts 2, 3 and 4 from the imidazole functionalized D-camphorsulfonamide 1.

NN NH

SO2 ORX-

NN NH

SO2 OR

anion exchange

R' SO3-

5: R = CH3 , R' = OC12H256: R = CH3 , R' = C16H337: R = C12H25 , R' = OC12H258: R = C12H25 , R' = C16H339: R = C16H33 , R' = OC12H2510: R = C16H33 , R' = C16H33

2: R = CH3 , X = I3: R = C12H25 , X = Br4: R = C16H33 , X = I

Scheme 3. Anion exchange reactions with the imidazolium salts 2, 3 and 4.



chain either on the cation or the anion show slightly higher phasetransition temperatures with Cr ? SmA transition temperatures inthe range 30–40 �C and the formation of the isotropic phase at93.7 �C and 107.7 �C, respectively. The highest phase transitiontemperatures were observed with compound 10 bearing hexadecylgroups both on the cation and on the anion (Table 1). These resultsindicate that in these long-chain substituted compounds, increas-ing length of alkyl tails leads to increased phase transition temper-atures. As a consequence, the thermal properties of the ioniccompounds can be controlled by a judicious choice of the chainlength of the alkyl groups both on the anion and the cation. Finally,the DSC thermograms also show that all compounds show a ten-dency to supercool before crystallization as it can be seen by theSm ? Cr transition in the cooling cycles which appears approxi-mately 15 �C below the Cr ? Sm transition in the heating cycles.Contrarily to the well-defined first order phase transitions, theglass transitions appear at relatively similar temperatures in allthermograms. We attribute these glass transitions mainly to dy-namic changes of the conformation of the alkyl chains while thelayered structure as shown Scheme 4 left, is preserved. Upon heat-ing, the SmA phase appears when the layers become bidimensionalfluids.

3.2.2. Polarizing optical microscopy (POM)The nature of the mesophase was determined under optical

microscopy. The double long-chain substituted imidazolium sulfo-nates and sulphates 7–10 showed, both from cooling of the isotro-pic melt or from heating of the crystalline solids, singleenantiotropic mesophases. Upon cooling to the LC state, the sam-ples displayed focal conic domains in a homeotropic background,characteristic of a thermotropic smectic A phase (Fig. 2, left). Undershearing, the samples showed oily streak textures (Fig. 2, right).However, no macroscopic indication for the formation of chiralmesophases was obtained. In particular the presence of a chiralsmectic phases was not detected.

ATG measurements with the compounds 7–10 (Supportinginformation) show that all imidazolium sulphates and -sulfonatesare thermally stable up to at least 200 �C, contrarily to severalother ionic liquids containing halide anions [55]. This high thermalstability is certainly due to the low nucleophilicity of the sulphateor sulfonate anions and makes these new chiral ionic liquid crys-tals interesting candidates as new (co-)solvents for ionothermalsyntheses.

3.2.3. X-ray diffraction (XRD)The characterization of the ionic compounds by XRD gave a

more detailed insight in the supramolecular structure within thematerials. Small angle X-ray scattering (SAXS) data were collectedfor the compounds 7–10 in the crystalline state at room tempera-ture and the liquid crystalline state. As an example, the SAXS pat-terns of compound 10 are shown in Fig. 3. The diffractogram ofcompound 10 obtained at room temperature (Fig. 3, left) clearlyshows a broad (1 0 0) reflection at q = 0.935 nm�1 together withsmaller reflections of higher order [(2 0 0), (3 0 0), (4 0 0)], indicat-ing that 10 exhibits a lamellar architecture in the crystalline statewith a d-spacing of 6.75 nm. This distance suggests an arrange-ment of the catanionic imidazolium sulphate in extended bilayersas illustrated on the left side of Scheme 4. The observed reflectionsare relatively broad indicating only short-range order. Upon heat-ing to the liquid crystalline state, the reflection shifts to larger an-gles indicating a shortening of the periodicity within the material(Fig. 3, right). In the case of compound 10, the d-spacing in theLC-state was found to be of 3.26 nm, representing a reduction ofmore than 50% of the initial value in the crystalline state. Thisstrong decrease indicates interdigitation both of the hydrophobic

Fig. 1. DSC traces of compounds 8 (lower) and 10 (upper). The figure shows the 3rd heating–cooling cycle of the compounds.

Table 1Phases transition temperatures and enthalpies (3rd heating and cooling cycle).

Compound Glass transitiontemperature (�C)

Phase transition temperatures (�C)(enthalpy DH (kJ/mol))

7 �5.8 Heating: Cr 20.8 (�25.7) Sm0X0 41.7 Cr0

64.0 SmA 79.6 (�1.81) IsoCooling: Iso 77.8 (1.94) SmA 5.1(22.2) Cr

8 �8.4 Heating: Cr 30.7 (�26.7) 64.0 SmA 93.7(�1.41) IsoCooling: Iso 93.5 (1.39) SmA 14.9 (26.9)Cr

9b �9.2 Heating: Cr 37.2a SmA 107.7 (�1.77) IsoCooling: Iso 106.5 (1.79) SmA 24.5a Cr

10 �8.8 Heating: Cr 55.7a Sm0X0 59.6 Cr0 80.5SmA 123.4 (�1.81) IsoCooling: Iso 121.4 (1.88) SmA 40.2a Cr

a Due to the superposition of different phase transitions, it is not possible todetermine the exact value of the Cr ? Sm0X0 enthalpy.

b Compound 9 shows additional phase transitions in the region 45–70 �C whichwe attribute to the formation of unidentified metastable smectic ‘X’ phases.



alkyl chains and the polar head groups as shown in Scheme 4. Sim-ilar tendencies were observed in the cases of the materials 7–9.

Table 2 summarizes the layer distances in the compounds 7–10in the crystalline and the LC state. The diffractograms of the com-pounds 7–9 can be found in the Supporting information.

The interlamellar distances obtained from the XRD character-ization of the compounds clearly show that the initial intersheetdistances in the crystalline state correspond to the summarizedlengths of the elongated alkyls chains of cation and anion. Thehighest distance was observed with compound 10 bearing twoC16 chains [8,52], whereas the smallest distance was observed inthe case of compound 7 containing two C12 chains [56]. Com-pounds 8 and 9 show intermediate distances.

The intersheet distance obtained by X-ray scattering exceeds byfar the length of the stretched alkyl chains of cations and anions.These lengths, obtained with Hyperchem software, are close to2.8 nm for 7, 3.0 nm for 8 and 9 and 3.3 nm for 10. This suggeststhat the crystalline phase consists of completely separated or onlyweakly interdigitated bilayers (sketched in Scheme 4, left). In thesmectic phase, a strong interdigitation of both alkyl chains and po-lar head groups results in an important decrease of the period

(Scheme 4, right). This reduction of the intersheet distances is par-ticularly weak in the case of compound 7 due to the presence ofrelatively small C12 chains. In the other ionic liquid crystals 8–10,the interdigitation led to a stronger decrease in the range of 3–3,5 nm, corresponding to a reduction of the periodicity withinthe materials between 51% and 55% (Table 2). These results arein agreement with the layer spacings observed for related long-chain substituted N,N0-di-alkyl-imidazolium salts [8,52].

The absence of a chiral mesophase can be understood from thelamellar morphology of the compounds in the LC-state. Part of thelayers act as buffers (either bearing the hydrophobic alkyl chains or

4,14 - 6,75nm

2,80 - 3,26nm

Scheme 4. Illustration of the melting of double bilayer assemblies of the ionic liquid crystals 7–10 in the crystalline state (left) to the mesophase (right). The bowls representpositively or negatively charged hydrophilic imidazolium or sulphate/sulfonates head groups which are randomly distributed in the layers.

Fig. 2. Polarized optical micrograph of compound 7 at 82 �C during melting showing focal conic textures (left); polarized optical micrograph of compound 9 at 106 �Cdisplaying oily streak textures upon shearing (right); bar = 50 lm.

Fig. 3. SAXS diffractograms of compound 10 at room temperature (left) and at 100 �C (right).

Table 2d-spacings in the compounds 7–10 in the crystalline and the LC state, obtained byXRD.

Compound d spacing/crystallinestate room temperature

d spacing (SmA-phase)/(temperature (�C))

Decrease(nm/%)

7 4.14 2.80 (70) 1.34/�338 5.88 2.86 (80) 3.02/�519 6.28 2.85 (80) 3.43/�55

10 6.75 3.26 (100) 3.49/�52



the ionic sublayer) and disable interactions between the sheetsbearing the chiral camphorsulfonamide substructures, leading toa random orientation of the chiral substructures from one layerto the next. These results are consistent with the DSC and XRDcharacterization of the compounds described above.

4. Conclusions

Catanionic surfactants are a relatively new class of ionic com-pounds which attracted considerable interest since Kaler and co-workers reported the spontaneous formation of stable vesicles inaqueous solution [36]. Here, we report new catanionic liquid crys-tals containing chiral camphorsulfonamide substructures. The newcompounds were synthesized by simple three step procedures inoverall yields of >90%. The physical properties of the new com-pounds reveal particular thermotropic behaviour. Contrarily tosimple long-chain substituted di-alkyl-imidazolium salts such as1-methyl-3-hexadecyl-imidazolium chloride [8,52,53], the long-chain substituted imidazolium halides bearing chiral camphorsulf-onamide groups do not form mesophases upon heating. Furtherstudies reveal the formation of liquid crystalline phases only fromcatanionic ionic liquid crystals when both cation and anion aresubstituted with long chain alkyl groups. However, the character-ization of the new compounds by XRD reveals the formation oflamellar phases with relatively low order. These results indicatethat the presence of chiral camphorsulfonamide units, which aredirectly anchored on the imidazolium cations, strongly affect thethermotropic properties of these substituted imidazolium salts.The chiral group

� disturbs the formation of thermotropic LC phases in the case ofthe imidazolium halides.� Leads to the formation of lamellar phases with relatively low

order in the case of the catanionic surfactants. The structuralorder is considerably lower than in the case of relatedlong-chain substituted di-alkyl-imidazolium alkylsulfonates[56].

These results clearly indicate that the nature of the ionic headgroups has high impact on the phase behaviour of catanionicsurfactants [57]. Finally, the chain length of the two alkyl groupspermits to tune the phase behaviour and to control the phasetransition temperatures of the salts. As already observed for otherimidazolium salts [58], longer alkyl chains increase the phasetransition temperatures. This feature is important in order toachieve ionic liquid crystals with controllable phase transitiontemperatures.

In conclusion, we introduce a new family of chiral catanionicliquid crystals. Besides the description of new these new com-pounds, this study advances the comprehension of the phasebehaviour of catanionic liquid crystals in general. All imidazoliumsulphates and -sulfonates are thermally stable up to at least 200 �C,which makes these new chiral ionic liquid crystals interesting can-didates as new (co-)solvents for ionothermal syntheses. However,the formation of chiral mesophases with these compounds wasnot observed, probably due to the lamellar bilayer structure inthe LC state.

Acknowledgments

A.T. thanks the scientific council of the ‘Ecole Nationale Supéri-eure de Chimie de Montpellier for a postdoctoral fellowship. P.H.thanks the ‘Groupement de Recherche PARIS’ and the ‘Réseau deRecherche 3, ‘Chimie pour le Développement Durable’ for financialsupport.

Appendix A. Supplementary material

Supplementary data associated with this article can be found, inthe online version, at doi:10.1016/j.jcis.2011.01.055.

References

[1] T. Welton, Chem. Rev. 99 (1999) 2071.[2] J. Fuller, R.T. Carlin, R.A. Osteryoung, J. Electrochem. Soc. 144 (1997) 3881.[3] J.G. Huddleston, H.D. Willauer, R.P. Swatloski, A.E. Visser, R.D. Rogers, Chem.

Commun. (1998) 1765.[4] M. Antonietti, D.B. Kuang, B. Smarsly, Z. Yong, Angew. Chem. Int. Ed. 43 (2004)

4988.[5] A. Elaiwi, P.B. Hitchcock, K.R. Seddon, N. Srinivasan, Y.M. Tan, T. Welton, J.A.

Zora, J. Chem. Soc. – Dalton Trans. (1995) 3467.[6] A. Mele, C.D. Tran, S.H.D. Lacerda, Angew. Chem. Int. Ed. 42 (2003) 4364.[7] S. Saha, S. Hayashi, A. Kobayashi, H. Hamaguchi, Chem. Lett. 32 (2003) 740.[8] A.E. Bradley, C. Hardacre, J.D. Holbrey, S. Johnston, S.E.J. McMath, M.

Nieuwenhuyzen, Chem. Mater. 14 (2002) 629.[9] T. Mukai, M. Yoshio, T. Kato, H. Ohno, Chem. Lett. 33 (2004) 1630.

[10] K. Binnemans, Chem. Rev. 105 (2005) 4148.[11] W. Dobbs, L. Douce, L. Allouche, A. Louati, F. Malbosc, R. Welter, New J. Chem.

30 (2006) 528.[12] M. Yoshio, T. Mukai, K. Kanie, M. Yoshizawa, H. Ohno, T. Kato, Adv. Mater. 14

(2002) 351.[13] C.K. Lee, H.W. Huang, I.J.B. Lin, Chem. Commun. (2000) 1911.[14] M.A. Neouze, J. Le Bideau, P. Gaveau, S. Bellayer, A. Vioux, Chem. Mater. 18

(2006) 3931.[15] J. Larionova, Y. Guari, C. Blanc, P. Dieudonne, A. Tokarev, C. Guerin, Langmuir

25 (2009) 1138.[16] C. Baudequin, D. Bregeon, J. Levillain, F. Guillen, J.C. Plaquevent, A.C. Gaumont,

Tetrahedron – Asymmetry 16 (2005) 3921.[17] C. Baudequin, J. Baudoux, J. Levillain, D. Cahard, A.C. Gaumont, J.C. Plaquevent,

Tetrahedron – Asymmetry 14 (2003) 3081.[18] J. Howarth, K. Hanlon, D. Fayne, P. McCormac, Tetrahedron Lett. 38 (1997)

3097.[19] K. Bica, P. Gaertner, Eur. J. Org. Chem. (2008) 3235.[20] M. Lombardo, M. Chiarucci, A. Quintavalla, C. Trombini, Adv. Synth. Catal. 351

(2009) 2801.[21] M. Lombardo, S. Easwar, F. Pasi, C. Trombini, Adv. Synth. Catal. 351 (2009) 276.[22] M. Lombardo, M. Chiarucci, C. Trombini, Chem. – Eur. J. 14 (2008) 11288.[23] J. Ding, T. Welton, D.W. Armstrong, Anal. Chem. 76 (2004) 6819.[24] P. Wasserscheid, A. Bosmann, C. Bolm, Chem. Commun. (2002) 200.[25] K. Bica, G. Gmeiner, C. Reichel, B. Lendl, P. Gaertner, Synthesis-Stuttgart (2007)

1333.[26] M.Y. Machado, R. Dorta, Synthesis-Stuttgart (2005) 2473.[27] K. Schneiders, A. Boesmann, P.S. Schulz, P. Wasserscheid, Adv. Synth. Catal. 351

(2009) 432.[28] R.A.F. Matos, C.K.Z. Andrade, Tetrahedron Lett. 49 (2008) 1652.[29] K. Nobuoka, S. Kitaoka, K. Kunimitsu, M. Iio, T. Harran, A. Wakisaka, Y.

Ishikawa, J. Org. Chem. 70 (2005) 10106.[30] A. Ouadi, B. Gadenne, P. Hesemann, J.J.E. Moreau, I. Billard, C. Gaillard, S. Mekki,

G. Moutiers, Chem. – Eur. J. 12 (2006) 3074.[31] B. Gadenne, P. Hesemann, J.J.E. Moreau, Tetrahedron – Asymmetry 16 (2005)

2001.[32] M. Trilla, R. Pleixats, T. Parella, C. Blanc, P. Dieudonne, Y. Guari, M.W.C. Man,

Langmuir 24 (2008) 259.[33] B. Gadenne, P. Hesemann, J.J.E. Moreau, Tetrahedron Lett. 45 (2004) 8157.[34] B. Gadenne, P. Hesemann, V. Polshettiwar, J.J.E. Moreau, Eur. J. Inorg. Chem.

(2006) 3697.[35] R.D. Koehler, S.R. Raghavan, E.W. Kaler, J. Phys. Chem. B 104 (2000) 11035.[36] E.W. Kaler, A.K. Murthy, B.E. Rodriguez, J.A.N. Zasadzinski, Science 245 (1989)

1371.[37] E. Marques, A. Khan, M.D. Miguel, B. Lindman, J. Phys. Chem. 97 (1993) 4729.[38] K. Horbaschek, H. Hoffmann, J.C. Hao, J. Phys. Chem. B 104 (2000) 2781.[39] C. Vautrin, T. Zemb, M. Schneider, M. Tanaka, J. Phys. Chem. B 108 (2004) 7986.[40] C. Vautrin, M. Dubois, T. Zemb, S. Schmolzer, H. Hoffmann, M. Gradzielski,

Colloids Surf. A 217 (2003) 165.[41] S. Svenson, Curr. Opin. Colloid Interface Sci. 9 (2004) 201.[42] F.X. Chen, L.M. Huang, Q.Z. Li, Chem. Mater. 9 (1997) 2685.[43] D. Lootens, C. Vautrin, H. Van Damme, T. Zemb, J. Mater. Chem. 13 (2003) 2072.[44] G.L. Lin, Y.H. Tsai, H.P. Lin, C.Y. Tang, C.Y. Lin, Langmuir 23 (2007) 4115.[45] Y.Q. Yeh, B.C. Chen, H.P. Lin, C.Y. Tang, Langmuir 22 (2006) 6.[46] Y. Haramoto, T. Miyashita, M. Nanasawa, Y. Aoki, H. Nohira, Liq. Cryst. 29

(2002) 87.[47] D. Tsiourvas, T. Felekis, Z. Sideratou, C.M. Paleos, Liq. Cryst. 31 (2004) 739.[48] M. Tosoni, S. Laschat, A. Baro, Helv. Chim. Acta 87 (2004) 2742.[49] C.V. Yelamaggad, M. Mathews, U.S. Hiremath, D.S.S. Rao, S.K. Prasad,

Tetrahedron Lett. 46 (2005) 2623.[50] J. Baudoux, P. Judeinstein, D. Cahard, J.C. Plaquevent, Tetrahedron Lett. 46

(2005) 1137.[51] Y.Z. Yousif, A.A. Othman, W.A. Almasoudi, P.R. Alapati, Liq. Cryst. 12 (1992)

363.



[52] A. Downard, M.J. Earle, C. Hardacre, S.E.J. McMath, M. Nieuwenhuyzen, S.J.Teat, Chem. Mater. 16 (2004) 43.

[53] L.B. Li, J. Groenewold, S.J. Picken, Chem. Mater. 17 (2005) 250.[54] T. Mukai, M. Yoshio, T. Kato, M. Yoshizawa, H. Ohno, Chem. Commun. (2005)

1333.

[55] B.K.M. Chan, N.H. Chang, M.R. Grimmett, Aust. J. Chem. 30 (1977) 2005.[56] M. Blesic, M. Swadzba-Kwasny, J.D. Holbrey, J.N.C. Lopes, K.R. Seddon, L.P.N.

Rebelo, Phys. Chem. Chem. Phys. 11 (2009) 4260.[57] B.F.B. Silva, E.F. Marques, J. Colloid Interf. Sci. 290 (2005) 267.[58] J.D. Holbrey, K.R. Seddon, J. Chem. Soc. – Dalton Trans. (1999) 2133.


Imidazolium camphorsulfonamides: Chiral catanionic liquid crystals with tunable thermal properties

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