Progress in liquid crystal chemistry
Since their discovery in 1888, liquid crystals have developed from a mere curiosity to a highly interdisciplinary research field. Liquid crystals are most widely used in electronic displays with further applications coming on to the market. One of the major issues in liquid crystal research is still the poor knowledge of structure-property relationships and thus the synthesis of whole series of structurally related compounds is required to design molecules with suitable physical properties. This Thematic Series addresses the synthetic challenges of liquid crystal research, as well as interdisciplinary aspects from material science, physics, physical and theoretical chemistry.
See also the Thematic Series:
Progress in liquid crystal chemistry II
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- Published 07 Oct 2009
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Figure 1: Phthalocyanine-C60 dyads 2a–d described in this paper, C60-derivative 1 (PCBM) and previously repor...
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Scheme 1: Synthesis of low-symmetry phthalocyanines 4a–d.
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Scheme 2: Synthesis of dyads 2a–d.
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Figure 2: UV–vis absorption spectra of 2a (black), 4a (blue) and 1 (red) in CH2Cl2.
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Figure 3: Cyclic voltammograms of 1 (red), 2a (grey), 2d (blue) and 3 (black) in CH2Cl2 (c = 10−4 M), scan ra...
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- Published 07 Oct 2009
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Figure 1: Schematic structure of a right-handed chiral nematic (cholesteric) phase. Black arrows represent th...
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Figure 2: Structures of the dopants investigated.
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Figure 3: Geometry of dopants 1–8. Structures were obtained from DFT calculations at the B3LYP/6-31g** level [58]...
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Figure 4: Helicity of the molecular surface of derivative 1 along its principal alignment axes in the liquid ...
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- Full Research Paper
- Published 07 Oct 2009
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Scheme 1: 1-[4-(dodecyloxy)phenyl]-3-methyl-1H-imidazol-3-ium mesogenic salts.
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Scheme 2: Synthesis of the imidazole A. Reaction conditions: (i) aryl iodide (1.37 mmol), imidazole (1.69 mmo...
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Scheme 3: Synthesis of methyl imidazolium 1a. Reaction conditions: (i) MeI in sealed tube, 54 h at RT.
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Figure 1: ORTEP view of compound 1a with partial labelling. The closest molecules are represented (with lower...
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Figure 2: Packing diagram of compound 1a in projection in the (b,c) lattice plane. Large spheres represent th...
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Scheme 4: Anion metathesis in water/CH2Cl2 as solvent.
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Figure 3: Spectra of absorption (red line) and emission (blue line) of 1a.
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Figure 4: TGA measurements of the compounds 1a–e (rate 10 °C·min−1, in air).
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Figure 5: Phase transition temperatures of compounds 1a–e.
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Figure 6: Powder X-ray diffraction pattern of compound 1a in the liquid crystal state (T = 120 °C).
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Figure 7: The melting process involves the ruffling of the ionic sublayer. In the smectic phase, the ruffling...
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Figure 8: Comparison of the molecular area S and of the ionic sublayer thickness dc (including mesogenic segm...
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Figure 9: Variation with the counter-ion of the molecular area S and of the ionic sublayer thickness dc (incl...
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Figure 10: Cyclic voltammogram of 1a in CH3CN (0.1 M NBu4PF6): (i), (ii) cathodic and anodic range of the volt...
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- Review
- Published 12 Oct 2009
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Figure 1: Molecular structure of NIRPAC: a Pd(II) complex based on Nile red and a curcumin derivative.
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Figure 2: Molecular structure of Pd(II) complexes based on functionalised 2-phenylquinolines and β-diketonate...
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Figure 3: Some unusual palladiomesogens based on 3,5-disubstituted-2,2′-pyridylpyrroles and β-diketonates.
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Figure 4: Molecular structure of Pt(II) complexes based on 4,4′-disubstituted 2,2′-bipyridines.
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Figure 5: Molecular structure of Zn(II) complexes based on polycatenar 4,4′-disubstituted 2,2′-bipyridines.
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Figure 6: Molecular structure of a gallium(III) mesogen.
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- Full Research Paper
- Published 21 Oct 2009
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Scheme 1: Synthesis of tetraphenylenes 2.
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Figure 1: DSC traces of compound 2h during (a) second cooling and (b) second heating (heating/cooling rate 5 ...
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Figure 2: Texture of 2h under the POM at 25 °C upon cooling from the isotropic liquid (heating/cooling rate 5...
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Figure 3: Molecular modelling of the saddle-shaped tetraphenylene (octakis)acyl core unit of 2 [35].
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Figure 4: Clearing temperatures Tcl [°C] of tetraphenylenes 2e–l as a function of the chain lengths n.
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Figure 5: The differences between the clearing temperatures Tcl [°C] of tetraphenylenes 2 and the melting poi...
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- Published 23 Oct 2009
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Figure 1: Schematic illustration of the main parts of the setup used in our lab for coaxial electrospinning a...
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Figure 2: Polarizing optical microscopy photographs of 8CB-containing composite fibres; (a) SmA phase at room...
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Figure 3: Microscopy photographs of characteristic samples when varying the flow rate of the liquid crystal
![[Graphic 1]](/bjoc/content/inline/1860-5397-5-58-i1.png?max-width=637&scale=1.18182)
in...
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Figure 4: Outer fibre diameters as a function of LC flow rate as determined from 50 measurements by optical m...
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Figure 5: DSC thermograms on heating of 8CB as bulk and as inclusion compound in PVP fibres produced with dif...
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Figure 6: The liquid crystal core shows a transformation from bubbly to smooth and to bubbly again with incre...
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Figure 7: Influence of the applied voltage and the flow rate of the polymer solution on the mean fibre diamet...
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Figure 8: a), b): 2D X-ray diffraction pattern of oriented fibres at two perpendicular roll-up directions sch...
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Figure 9: X-ray diffraction patterns of PVP fibres without LC (a) and of surface-aligned samples of bulk 8CB ...
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Figure 10: Schematic sketch of the arrangement of LC molecules and the smectic layers in an electrospun fibre.
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- Full Research Paper
- Published 06 Nov 2009
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Scheme 1: Mesogenic imidazolium synthesis [Reaction conditions: (i) DMF, K2CO3, BrCnH2n+1, 60 °C, overnight; ...
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Scheme 2: Anion exchange in water.
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Figure 1: 1H NMR spectrum (in CD2Cl2) of 110–610.
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Figure 2: TGA measurements of wet and water free 112 imidazolium salt.
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Figure 3: TGA measurements of the two entire series 110–610 and 114–614 (rate 10° C·min−1, in air).
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Figure 4: Transition temperatures of 114–614 as a function of the anion (Cr = crystal; SmA: smectic A phase; ...
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Figure 5: (a) Illustration of a single homeotropic monodomain, which is observed as a black isotropic texture...
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Figure 6: Diffraction small-angle X-ray pattern of the smectic phase of 212 recorded at T = 100 °C.
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Figure 7: Variation with the counter-ion of the molecular area S and of the ionic sublayer thickness dc (incl...
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Figure 8: Grazing incidence X-ray pattern at 100 °C on the top of a 312 droplet, slowly cooled down from isot...
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Figure 9: Variations with chain length of the maximum molecular areas close to isotropization Smax and of the...
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- Published 09 Nov 2009
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Scheme 1: Comparison of mesomorphic properties of 1a and 2a.
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Scheme 2: Variation of spacer lengths and terminal group at 5-phenylpyrimidine.
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Scheme 3: Synthesis of compounds 3–5, 9 and 11.
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Scheme 4: Synthesis of compounds 6 and 7.
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Figure 1: DSC curve of compound 3d (heating/cooling rate 10 K/min).
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Figure 2: Fan-shaped texture of 3e under crossed polarizers upon cooling from the isotropic liquid (magnifica...
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Figure 3: DSC curve of compound 4e (heating/cooling rate 5 K/min).
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Figure 4: Fan-shaped texture of compound 4d at 45 °C upon cooling from the isotropic liquid (cooling rate 1 K...
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Figure 5: DSC curve of compound 6c (heating/cooling rate 10 K/min).
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Figure 6: Fan-shaped texture of compound 6e at 45 °C upon cooling from the isotropic liquid (cooling rate 10 ...
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Figure 7: Comparison of the mesophase range ΔT for the different spacer lengths of compounds 3, 4 and 6: meso...
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Figure 8: Comparison of the mesophase range ΔT for the different spacer lengths of compounds 3, 4 and 6: meso...
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Figure 9: Proposed model for the layer structure.
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- Published 13 Nov 2009
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Figure 1: Structure of different liquid crystalline phases build with two kinds of hard spherocylinders with ...
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Scheme 1: Chemical formulas and phase sequences of the mesogens PhP14, 6PhPz and 2PhP and the chiral dopant M...
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Figure 2: Molecular structure of the mesogens PhP14, 6PhPz and 2PhP differing in molecular lengths by a facto...
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Figure 3: Phase diagram of the system 2PhP/PhP14. Over a broad temperature and concentration range only the S...
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Figure 4: The layer spacing in the SmA phase at T = Tc vs mole fraction for the system 2PhP/PhP14 (filled tri...
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Figure 5: Reduced layer spacing for the mixtures which exhibit SmA and SmC phases in the system 2PhP/PhP14. P...
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Figure 6: Textures of the mixture with 65% PhP14 in 2PhP as observed in the polarizing microscope. The upper ...
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Figure 7: Tilt angle vs temperature difference to the phase transition temperature for pure PhP14 (filled tri...
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Figure 8: The translational order parameter Σ in the SmA phase is plotted vs the reduced temperature 1 – T/Tc...
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Figure 9: Phase diagram of the system 6PhPz/PhP14. Over a broad temperature region only the SmA phase is stab...
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Figure 10: Reduced layer spacing vs temperature difference to the phase transition temperature for the mixture...
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Figure 11: Schematic sketches of different models for smectic A ordering of bidisperse mesogens. Different mod...
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- Full Research Paper
- Published 04 Dec 2009
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Figure 1: Uniaxial nematic (left) and biaxial nematic (right) phases and their corresponding indicatrices.
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Figure 2: Design of V-shaped, shape-persistent oligo(phenylene ethynylene) mesogens of type I and II (R, R′ =...
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Scheme 1: Synthesis of arm derivatives 6. Reaction conditions: (i) 1) Pd(PPh3)4, CuI, piperidine, rt; 2) TBAF...
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Scheme 2: Two-step synthesis of V-shaped nematogens: symmetric (1) and non-C2-symmetric (2) thiadiazoles. Rea...
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Figure 3: Comparison of the mesophase ranges of intermediate hockey stick compounds 3 and symmetric V-shaped ...
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Figure 4: Comparison of the thermal behaviour of symmetric and non-symmetric V-shaped molecules. The molecule...
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Figure 5: Textures of the nematic phase of 2c. a) Schlieren texture at 173 °C. b) and c) Planar alignment on ...
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Figure 6: X-ray study of nematic mesophases from V-shaped mesogens. A: Diffraction pattern of 2c at 70 °C. B:...
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- Published 30 Dec 2009
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Figure 1: The molecular structures of 1,12-dicarba-closo-dodecaborane (12-vertex p-carborane, A) and 1,10-dic...
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Figure 2: The molecular structures of derivatives 1–20.
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Scheme 1: Preparation of diesters 16[n].
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Scheme 2: Preparation of esters 18–20.
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Scheme 3: Preparation of phenol 24.
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Figure 3: Partial DSC trace for 16D[6]. Heating rate 5 K/min.
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Figure 4: Optical textures of 16D[6] obtained for the same region of the sample upon cooling: (a) SmA growing...
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Figure 5: The change in the clearing temperature ΔTc upon substitution –OCH2– → –CH2CH2– in selected pairs of...
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Figure 6: The change in the clearing temperature ΔTc upon replacing of the –OCH2– connecting group with anoth...
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Figure 7: Equilibrium ground state geometries (B3LYP/6-31G(d)) for benzene derivatives: ethoxybenzene (25), p...
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- Published 07 Jan 2010
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Figure 1: The orientational correlation function as a function of separation r between LC molecules for (a) 2...
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Figure 2: Correlation length ξ as a function of 1/B for homogeneous and random samples for three different co...
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Figure 3: The s(B) dependence for homogeneous and random samples for two different p in (a) 2D and (b) 3D. Fo...
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Figure 4: The m(B) dependence r homogeneous and random samples for two different p in (a) 2D and (b) 3D. In t...
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Figure 5: The crossover field Bc on varying p. Indicated lines roughly separate ergodic (B > Bc) and nonergod...
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- Full Research Paper
- Published 20 May 2010
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Scheme 1: Hexapentyloxytriphenylene (HAT5).
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Figure 1: Optical microscopy textures of a film prepared by drop-casting on heating to the isotropic phase an...
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Figure 2: Optical microscopy images of a spin-coated sample with linear structures thick enough to be detecte...
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Figure 3: AFM scan of a thick rope, of similar size to the linear structures observed by optical microscopy. ...
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Figure 4: Thinner, isolated fibers, similar to the ones constituting the larger rope in Figure 3 are present in other...
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Figure 5: Small, elongated aggregates form a nematic-like texture, possibly due to the formation of a lyonema...
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Figure 6: AFM image of a spin-coated sample from a solution of 6 mg/ml. Below the surface profile along the w...
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Figure 7: AFM image of the sample prepared from a concentration of 3 mg/ml.
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Figure 8: Surface topography of the sample prepared from a concentration of 1.5 mg/ml visualized by AFM. The ...
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Figure 9: Higher resolution scans of the fiber structure of the low concentration sample.
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- Full Research Paper
- Published 07 Jul 2010
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Figure 1: Nematic orientational correlation function G(r) for different values of x (x = 0.01 and 0.25), N = ...
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Figure 2: (a) The nematic domain length ξ, (b) the domain dispersion parameter m, and (c) the range parameter...
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Figure 3: Degree of biaxiality β2 as a function of x; JLC–NP: −1, −2, and −4; JLC–LC = JLC–NP = 1, N = 80 × 8...
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