Molécules discoïdes et polymorphisme mésomorphe

Destrade, C.; Gasparoux, H.; Foucher, P.; Tinh, Nguyen Huu; Malthête, Jacques; Jacques, J.

doi:10.1051/jcp/1983800137

Cited by 65 publications

(31 citation statements)

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“…[6]) AO = 2ird(ne n0)11, (3) where A is the wavelength of the polarized light. The ordinary refractive index is not dependent on rotation of n in the xz plane, whereas the extraordinary refractive index depends on the rotation of n as given by no = n1; ; = n11n_LI(r4cos2 0 + ni sin' 0)1/2, (4) where n, and no are the refractive indices perpendicular and parallel to the director, respectively, and 0 is the angle between the director and the direction of the magnetic field. In order to obtain information about the elastic constants we need to know the optical anisotropy An = no n. The value of An will be negative because the director is perpendicular to the molecular plane.…”

Section: H3comentioning

confidence: 99%

“…These materials show a normal sequence in the occurrence of different mesophases. When cooling the isotropic liquid of these triphenylene derivatives, nematic, columnar and crystalline phases are obtained (see figure 1), in contrast to the alkanoyloxytruxenes which exhibit an inverted nematic phase, viz, a nematic phase at a lower temperature than a columnar phase [3,4]. In order to investigate whether the results found for the inverted nematic phase, exhibited by the truxene derivatives, are characteristic for the behaviour of nematics consisting of discoid molecules we have studied the normal nematic phase exhibited by these triphenylene derivatives.…”

Section: Introductionmentioning

confidence: 99%

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Measurements of the ratio of the Frank constants for splay and bend in nematics of disc-like molecules

1987

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Section: H3comentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Measurements of the ratio of the Frank constants for splay and bend in nematics of disc-like molecules

1987

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“…Thus it appears that copper laurate is the first example of a thermotropic hexagonal discotic mesogen containing only four peripheral chains. The currently accepted view is that six peripheral chains at least are required for a discoid molecule to exhibit a two-dimensional hexagonal lattice [10,11]. (2) It is important to note that, up to now, we have not been able to detect the harmonic reflection at 4.7/2 A for instrumental reasons.…”

mentioning

confidence: 94%

“…Our interest in the thermotropic mesophases of transition metal complexes [6][7][8] [9], and were later found with mesophases of flat disc-like molecules now known as discotic liquid crystals [10,11]. In both cases, the structure corresponds to the stacking of molecules in columns, these being surrounded by aliphatic chains in a disordered state and arranged in a two-dimensional hexagonal lattice.…”

mentioning

confidence: 99%

Discotic mesophase of copper(II) laurate

et al. 1984

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“…For example, the columnar phases have been divided into four basic groups because of their different lattice structures; e.g. D hd , D h0 , D rd and D obd [2], The series of hexa-O-alkanoyl-scyllo inositoles (HASI) is of interest because disc-like molecules with alicyclic saturated cores were recently found to form discotic phases [3,10]. The aim of this paper was to study various parameters of the mesogenic phases of those compounds.…”

Section: Introduetionmentioning

confidence: 99%

X-Ray Diffraction Studies on Alicyclic Saturated Discotic Liquid Crystals

Neuling

Stegemeyer

Praefcke

et al. 1987

Zeitschrift Für Naturforschung A

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Dedicated to Professor Ernst Fischer on the occasion of his 65th birthdayThe discotic liquid crystalline phase of a new class of disc-like molecules (hexa-O-alkanoylscyllo-inositoles) is studied by small angle X-ray scattering, DSC and optical observations. Comparison of these three methods allows the determination of the structural arrangement. X-ray film exposures of oriented samples clearly demonstrate the hexagonal columnar ordered type of mesophases. A simple model calculation shows that the alkyl chains of neighbouring columns interpenetrate each other to a small extent. IntroduetionThe different ways in which disc-like molecules can be arranged in the discotic mesomorphic state have recently been the subject of many investiga- [2], The series of hexa-O-alkanoyl-scyllo inositoles (HASI) is of interest because disc-like molecules with alicyclic saturated cores were recently found to form discotic phases [3,10]. The aim of this paper was to study various parameters of the mesogenic phases of those compounds. Especially the intercore distance d of the columns, the temperature dependence of d and the influence of the alkyl chain lengths on the mesomorphic behaviour have been measured. ExperimentalThe compounds of the homologous series of HASI (alkyl chain length from n = 5 to n = 11) were synthesized and puriFied as described elsewhere [3,9]. The samples were filled in Lindemann capillaries (diameter 1 mm) and then placed into a tight-fitting rectangular brass holder (20 x 5 x 2 mm). The orientation was performed using a magnetic Field strength up to 2.4 Tesla in a Drusch electromagnet. The temperature and cooling rate (0.2 K/min) was controlled by a modified Mettler FP 52 heating stage (all magnetic materials have been replaced by aluminium). The direction of the magnetic field was perpendicular to the long axis of the capillary. The X-ray measurements were performed using small angle cameras of the type Kratky-Compact (A. Paar, Graz, Austria) and Kiessig (Seifert, Ahrensburg, FRG). We used film registration and detection by a curved linear position sensitive proportional counter PSPC (M. Braun. Munich) with an active length of 50 mm and a low flux of a mixture of 75% argon and 25% methane under a pressure of 11 bar. In order to calibrate the detector, the scattering curve of a cadmium-distearate multilayer (35 double layers) has been recorded at room temperature before each measurement. This calibration sample was prepared on a glass rod of 2 mm diameter using the Blodgett technique [4], Its diffraction pattern consists of sharp reflections with a First order period of d= (5.03 ± 0.01) nm [5], Ni-Filtered Cu-radiation was used. The temperature in the Kratkycompact camera was controlled by an electronic heating stage (A. Paar, Graz, Austria) with a relative accuracy of ± 0.02 K. In the Kiessigcamera we used a thermostated water flow cell with 0932-0784 / 87 / 0600-0611 S 01.30/0. -Please order a reprint rather than making your own copy.

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Molécules discoïdes et polymorphisme mésomorphe

Cited by 65 publications

References 0 publications

Measurements of the ratio of the Frank constants for splay and bend in nematics of disc-like molecules

Measurements of the ratio of the Frank constants for splay and bend in nematics of disc-like molecules

Discotic mesophase of copper(II) laurate

X-Ray Diffraction Studies on Alicyclic Saturated Discotic Liquid Crystals

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