Progress in liquid crystal chemistry II
Since our initial Thematic Series "Progress in liquid crystal chemistry" in 2009, the research field has further broadened and stretches currently from materials science, through energy conversion and storage, to life sciences. The review articles and original research papers of this second Thematic Series in the Beilstein Journal of Organic Chemistry, written by known experts of their field, cover diverse topics such as novel discotic and calamitic compounds, bent-core mesogens, amphiphiles, and liquid-crystalline nanoparticles. It is our goal to give the reader insight into both synthetic aspects of liquid-crystal chemistry as well as application-oriented properties, such as photoconductivity or chirality transfer, to name just a few selected examples.
- Full Research Paper
- Published 24 Jan 2012
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Scheme 1: (Top) original synthesis of compound 7a from thiophene (Oc = n-octyl) [19]. (Below) shortened synthesis...
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Scheme 2: Effect of bulky α-alkyl substituents on the base-initiated cyclo-oligomerisation of phthalonitriles....
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Figure 1: Comparison of the phase behaviours of the α-substituted phthalocyanines with n-alkyl [25] and isoalkyl ...
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Figure 2: Optical micrographs taken with crossed polarisers and at a magnification of × 20. (a) n-Octyl deriv...
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Figure 3: (a) Time-of-flight hole transits for an ITO/7c/ITO cell with the liquid crystal in its Colh phase a...
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- Full Research Paper
- Published 24 Jan 2012
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Scheme 1: Examples for bent mesogens containing salicylideneimine moieties.
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Scheme 2: Synthetic pathway to prepare compounds OH 1.
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Figure 1: Polarising optical microscopy images. a) Compound OH 1a: Grainy texture with smectic Schlieren area...
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Figure 2: X-ray diffraction pattern of a powderlike sample of OH 1b at 131 °C (inset: Small angle region; low...
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Figure 3: Electro-optical behaviour of compound OH 1a: a) current response curve (U = 182 Vpp, f = 30 Hz, T =...
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Figure 4: Switching behaviour of compound H 1a, which depends on how quickly the electric field is switched o...
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Scheme 3: Reaction pathways to prepare the monosalicylideneaniline compounds OH 2a–j.
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Figure 5: Compound OH 2a: Texture of the SmCP phase at 126 °C.
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Figure 6: a) 2D X-ray pattern of a surface-aligned sample of compound OH 2a at 128 °C (lower part of the patt...
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Figure 7: Electro-optical switching behaviour of compound OH 2a: a) current response (U = 230 Vpp, f = 25 Hz, ...
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Scheme 4: Synthetic steps followed to prepare the compounds OH 3 and OH 4.
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Figure 8: Optical photomicrographs of compound OH 3a: a) On cooling of the isotropic liquid; c) U = 0 V; b) U...
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Figure 9: Electro-optical behaviour of compound OH 3a: a) Current response curve (U = 308 Vpp, f = 35 Hz, T =...
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Figure 10: Growth of a fan-shaped texture from lancetlike filaments upon cooling of the isotropic liquid of co...
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Figure 11: a) 2D X-ray pattern of a surface-aligned sample of compound OH 3b at 160 °C (lower part of the patt...
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Figure 12: Compound OH 3b: Texture of the SmCPA phase in dependence on the polarity of the applied D.C. field.
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Figure 13: Compound OH 4b, exhibiting a fan-shaped texture together with a Schlieren texture upon cooling of t...
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Figure 14: 2D X-ray diffraction pattern of a partially surface-aligned sample of OH 4b at 115 °C (inset: Small...
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Figure 15: Switching behaviour of compound OH 4b at 120 °C: a) Current response curve (U = 116 Vpp, f = 40 Hz, ...
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Figure 16: Compound OH 4d: a) Microphotograph of a growing fringe pattern of a SmCP phase upon cooling of the ...
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Figure 17: Electro-optical behaviour observed on the fan-shaped texture of compound OH 4d; UD.C. = 47 V; T = 1...
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Figure 18: a) 2D X-ray diffraction pattern for a surface-aligned sample of OH 4d at 122 °C on cooling; b) χ-sc...
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Scheme 5: Reaction steps employed for the preparation of the compounds OH 5 and OH 6.
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Figure 19: Compound OH 5d: Optical photomicrographs of chiral domains at 122 °C; polariser and analyser are un...
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Figure 20: Compound OH 5b: a), b) Chiral domains at 175 °C, 0 V, polarisers uncrossed by about ±8° from the 90...
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Figure 21: X-ray diffraction patterns of compounds OH 5: a) Pattern of a powderlike sample of compound OH 5g a...
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Figure 22: Photomicrographs of compound OH 5f: a) Appearance of spiral filaments on slow cooling of the isotro...
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Figure 23: Current response of compound OH 6b exhibiting two repolarisation peaks proving an antiferroelectric...
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Figure 24: On cooling the isotropic liquid phase of compound OH 6c; a Schlieren texture together with fringe p...
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Figure 25: Electro-optical behaviour of compound OH 6c: a) Current response (UA.C. = 17 V/µm, f = 39 Hz, T = 1...
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- Full Research Paper
- Published 24 Jan 2012
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Figure 1: Chemical structure of the helical perylenequinones under investigation: Cercosporin (1) and phleich...
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Figure 2: Newman projections of the conformational states of the side chain linked at C1 of cercosporin (1), ...
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Figure 3: “Propeller” (left) and “double butterfly” geometry (right) of the g+ g+ conformer of 1, as obtained...
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Figure 4: Optimized geometry of all conformers of 1 (upper half) and 2 (lower half), obtained at the DFT/M06-...
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Figure 5: Chirality parameter Q (diamonds) and probability distribution (bars), calculated for all conformers...
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- Full Research Paper
- Published 20 Feb 2012
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Figure 1: Selected methods for the preparation of arylhydrazines I through hydrazides II.
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Figure 2: The structures for hydrazines 1a–1h.
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Scheme 1: Formation and deprotection of 3a under reductive conditions.
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Scheme 2: General mechanism for the deprotection of arylhydrazides. G represents a substituent.
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Figure 3: Structure of hydrazide 2a.
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Scheme 3: Synthesis of arylhydrazines 1. Substituents X and Y are defined in Figure 2.
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Scheme 4: Preparation of bromide 5a.
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Scheme 5: Preparation of 5b.
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Figure 4: The structure of verdazyl radical 9 and a texture of the Colr phase.
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- Review
- Published 08 Mar 2012
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Figure 1: Three of the common molecular and supramolecular structural motifs in liquid crystal chemistry: rod...
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Figure 2: Schematic representation of the solvent-mediated ligand exchange process, illustrated for the parti...
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Figure 3: Chemical structures and LC properties of the rodlike ligands discussed in the text.
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Figure 4: Schematic representation of pseudospherical Au NPs coated exclusively with mesogenic rodlike ligand...
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Figure 5: TEM images of Au@612 (a) before and (b) after thermal treatment. Below: Proposed model of the nanop...
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Figure 6: Ligand deformation at the surface of the gold NPs giving rigid "poles" and a soft equator. Such def...
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Figure 7: A simplified illustration of the local rectangular arrangement of nanoparticles in a condensed mixe...
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Figure 8: Chemical structures and LC properties of the rodlike ligands discussed in the text.
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Figure 9: Schematic drawing of the arrangement of nanoparticles in the columnar phase, as viewed from above (...
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Figure 10: The proposed structural models resulting from ligand migration at the NP surface: (a) Smectic (Au@C6...
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Figure 11: Reversible migration of the surface ligands as a function of temperature (and phase). Only the blue...
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Figure 12: Photochromic and photo-mesogenic rodlike ligands.
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Figure 13: Chemical structures and LC properties of side-on mesogens used to coat NPs.
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Figure 14: Left: POM image of ligand 12. Right: POM image of Schlieren texture of the hybrid Au@12. Reprinted ...
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Figure 15: Threaded nematic texture of Au@ C12/13 as observed by POM at RT. Scale bar = 10 μm. Reprinted with ...
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Figure 16: Schematic representation of the gold NP columnar structures. (a) Rhombohedral phase in Au@C12/13 an...
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Figure 17: TEM images of thin films of the
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phase of Au@C12/13 recorded with the beam (a) parallel to the ![[Graphic 6]](/bjoc/content/inline/1860-5397-8-39-i6.png?max-width=637&scale=1.18182)
pla...
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Figure 18: Chemical structures and mesogenic properties of bent-core proto-mesogenic ligands used to coat NPs.
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Figure 19: Chemical structures and mesogenic properties of dendritic and proto-dendritic ligands used to coat ...
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Figure 20: TEM image showing the arrangement of the hybrid NPs Au@16 into regularly spaced rows. Reprinted wit...
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Figure 21: Chemical structures and mesogenic properties of dendritic and proto-dendritic ligands used to coat ...
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Figure 22: Top left: Body-centred (I) cubic lattice of
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symmetry composed of truncated octahedrons. Top right:...
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Figure 23: Model proposed for the organisation of the hybrids within the quasi-nematic mesophase. Reprinted wi...
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Figure 24: Mesogenic dendrons used to coat Au NPs.
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Figure 25: Chemical structures of the discotic mesogenic ligands used to coat NPs.
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Figure 26: TEM images of Au@235,12 prepared from aged solutions stood for 10 days in solutions of (a) 1:1 MeOH...
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Figure 27: Some of the various hybrid geometries and packing motifs possible upon ligand grafting to the surfa...
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- Full Research Paper
- Published 09 Mar 2012
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Scheme 1: Diketonato metallomesogens and diketones with mesomorphic properties.
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Scheme 2: Malonates and cyanoacetates tethered to calamitic 4-cyanobiphenyl units.
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Scheme 3: Synthesis of malonate and cyanoacetates tethered to 4-cyano-biphenyl moieties.
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Figure 1: DSC traces of 13a (heating/cooling rate 5 K/min).
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Figure 2: DSC traces of 11a (heating/cooling rate 10 K/min).
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Figure 3: Schlieren textures of 11a and 11b under crossed polarizers, upon cooling (cooling rate 5 K/min) fro...
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Figure 4: Schlieren textures of 13a and 13b under crossed polarizers upon cooling (cooling rate 5 K/min) from...
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Figure 5: 2D X-ray scattering patterns of 11a: (A) crystalline phase at 50 °C, (B) isotropic phase at 25 °C, ...
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- Published 16 Mar 2012
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Figure 1: Overall molecular structure of the perhydroazulene core with trans-stereochemistry.
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Scheme 1: Stereochemistry of carbene adducts 1a and 1b.
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Scheme 2: Preparation of the tropylidenes 4a and 4b.
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Scheme 3: Formation of esters 5a and 5b and the corresponding acids 6a and 6b.
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Scheme 4: Preparation of 8a and 8b.
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Scheme 5: Preparation of 10a and 10b.
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- Published 30 Mar 2012
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Scheme 1: Structures of the investigated ABA-heterotrimesogens CB-Ox-CB/n and heterodimesogens CB-Ox/n, Thia-...
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Scheme 2: Synthesis of the ABA-heterotrimesogens CB-Ox-CB/n.
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Scheme 3: Synthesis of the dimesogens CB-Ox/n and Thia-Ox/n.
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Figure 1: XRD pattern of a (partially) surface-aligned sample of the N phase of compound CB-Ox-CB/4: (a) diff...
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Figure 2: Dimesogen CB-Ox/4: (a) DSC traces obtained during initial heating and cooling cycles scanned at a r...
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Figure 3: XRD data of the dimesogen CB-Ox/4: (a,b) diffraction patterns of a magnetic-field-aligned sample (t...
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Figure 4: Models showing the suggested organizations of dimesogens in the smectic phases and in the preferred...
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Figure 5: Dimesogen Thia-Ox/5: (a) DSC traces obtained during first heating and cooling cycles scanned at a r...
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Figure 6: XRD data of the SmC phase of the dimesogen Thia-Ox/5: (a) diffraction pattern at T = 160 °C; (b) χ-...
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Figure 7: XRD pattern of a magnetic-field-aligned sample of the NcybC phase of the dimesogen Thia-Ox/10: (a) ...
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Figure 8: Comparison of the optical textures of distinct types of 1,2,4-oxadiazole based dimesogens as observ...
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- Full Research Paper
- Published 04 May 2012
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Scheme 1: Preparation of carbene adducts 4 [18] and 5.
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Scheme 2: Preparation of the cycloheptatrienes 7 and 8 [18,20].
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Scheme 3: Preparation of derivatives 9 and 10.
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- Published 19 Jul 2012
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Figure 1: Smectic A phase of a mixture of two mesogens differing strongly in molecular length. Left: The laye...
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Scheme 1: Chemical structures and phase-transition temperatures of the mesogens 2PhP and PhP16 and of the chi...
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Figure 2: Molecular structures and molecular lengths of 2PhP and PhP16. The longer mesogen PhP16 is approxima...
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Figure 3: The phase diagram of the binary mixture system PhP16/2PhP.
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Figure 4: The layer spacing obtained by SAXS-measurements in the SmA phase at T = Tc is plotted against the m...
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Figure 5: Reduced layer spacing d/dA versus temperature difference to the phase-transition temperature T−Tc f...
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Figure 6: The tilt angle θ is plotted against the temperature difference to the phase-transition temperature T...
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Figure 7: Translational order parameter Σ in the SmA phase versus temperature difference to the phase-transit...
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Figure 8: Textures of the pure compound PhP16 on cooling. Left: SmC phase at 96.8 °C Right: same positions in...
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Figure 9: Integrated intensity profile of an unoriented sample of PhP16 at T = 82.5 °C in the SmF phase.
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Figure 10: (a) WAXS-measurement of the SmF phase of PhP16 at T = 82 °C with the smectic-layer normal k oriente...
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Figure 11: (a) WAXS-measurement of the SmF phase of PhP16 at T = 88 °C with the smectic layer normal oriented ...
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Figure 12: (a) Layer spacing of the SmF and the SmC phase of the pure compound PhP16 in dependence of the temp...
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- Full Research Paper
- Published 05 Jun 2013
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Scheme 1: Complementary guanidinium sulfonate 1 and guanidinium–sulfonimide ion pairs 2 and 3.
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Scheme 2: Synthesis of the potassium sulfonimides 6a and 6b.
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Scheme 3: Synthesis of guanidinium sulfonimides 2a,b, 3a,b and iodides 7∙I, 8∙I.
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Figure 1: DSC traces of compound 3b (heating/cooling rate 10 K min−1).
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Figure 2: Compound 3b under crossed polarizers upon cooling from the isotropic melt (200-fold magnification)....
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Figure 3: (a) WAXS diffraction pattern of 3b at 59.5 °C (vertical magnetic field director); (b) temperature-d...
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