Columnar to Nematic Mesophase Transition: Binary Mixtures of Copper Soaps with Hydrocarbons

Seghrouchni, Rachid; Skoulios, A.

doi:10.1051/jp2:1995189

Cited by 21 publications

(16 citation statements)

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“…To find similarities with the nematic-columnar lyotropic polymesomorphism of the swelled mixtures [13,14], observations were carried out on several more dilute solutions in acid, with no success. This points to a simpler binary acid-organic salt phase diagram.…”

Section: Resultsmentioning

confidence: 99%

“…Because of the decomposition of the compounds prior to the clearing point, optical microscopy was carried out on the lyotropic columnar phases of the higher members of the series (n~8, 12, 18, 20, 22, and 24) by swelling the samples with various organic solvents (hydrocarbons, toluene), finding a first order transition from the columnar discotic to discotic nematic phase, at more dilute concentrations [13,14]. Mesophases were shown by XRD to be columnar discotic above the butyl homologue.…”

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confidence: 99%

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Short chain copper(II)n-alkanoate liquid crystals

et al. 2004

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Four short chain members of the copper(II) n-alkanoate series Cu(Cn) 2 , from propanoate to hexanoate, have been synthesized, purified and characterized by means of optical microscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), FTIR and Raman spectroscopy. The TGA study shows that decomposition starts on heating above 420-470 K (depending on the sample) in a nitrogen atmosphere. In addition, thermal decomposition was investigated by DSC using special high pressure pans and endo-and excthermic processes were found which have not been reported previously. All but one of the compounds melt to a liquid crystal phase, which decomposes before the clearing point. The exception is the propanoate homologue, which decomposes directly from the solid state. Despite this problem of sample decomposition, the identification by optical microscopy of the tetragonal (butanoate) and hexagonal (pentanoate and hexanoate) discotic columnar phases was, for first time, possible by the addition of small amounts of the corresponding acid to the samples. These results are in agreement with the X-ray diffraction study performed using swelled mixtures of these salts with hydrocarbon solvents. Two solid-solid transitions, not previously reported in the literature, were found for the butanoate homologue at 395.9 and 422.9 K with DH~8.27 and 1.37 kJ mol 21 , respectively. The solid and liquid crystalline phases were investigated using variable temperature FTIR spectroscopy.

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Section: Resultsmentioning

confidence: 99%

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Short chain copper(II)n-alkanoate liquid crystals

et al. 2004

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“…21 Thus, the column spacing of the columnar discotic phase increases with the acid concentration (see Figure SI.6 of the SI).…”

Section: Crystal Growth and Designmentioning

confidence: 98%

Study of the Polymorphism in Copper(II) Decanoate through Its Phase Diagram with Decanoic Acid, and Texture of the Columnar Thermotropic Liquid Crystal Developable Domains in This and Similar Systems

Riesco¹,

Martínez-Casado

Cheda³

et al. 2014

Crystal Growth & Design

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A new third polymorph of copper(II) decanoate has been found by two methods: from the crystallization of the salt− acid solution and from a specific thermal treatment of the polymorph obtained in n-heptane. The new polymorph, whose crystal structure has been solved for the first time, is the most stable from the thermodynamic point of view. It presents a bilayer structure, but with two different types of paddle-wheels catenae with opposite orientations. This polymorphism as well as the temperature vs composition phase diagram of the system, [(1 − x) C 9 H 21 CO 2 H + (x) (C 9 H 21 CO 2 ) 2 Cu], were solved by differential scanning calorimetry, Fourier transform infrared spectroscopy, Xray diffraction, pair distribution function, and optical microscopy. The singularities of the phase diagram are (a) a Krafft-like process of molecular association of the copper(II) decanoate into the acid solution, at about T = 361.5 K and x = 0.022 (forming salt-acid adducts of 1:1 stoichiometry); (b) a fusion transition as an invariant (T = 379.1 K) of the solid salt in excess from the copper(II) decanoate crystal phase to the discotic liquid crystal, forming homeotropic developable domains (seen for the first time in these systems) of the pure salt into the saturated acid solution. These domains are seen not only in the copper(II) decanoate but also in other members of the series, at high salt concentration in the corresponding acid solution, and allow identification of the hexagonal columnar discotic structure of the mesophase (with the exception of the copper(II) butanoate, where the tetragonal domains with tilted disks, paddle-wheels, were seen in the same salt−acid region).

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“…Prior efforts to template oxide materials into opals relied on the hydrolysis of neat metal alkoxides soaked into the pores of the structure. [11,12,19,20] Although this procedure works well for monolithic samples, when applied to thin films it deposits an inhomogeneous layer on their surfaces that produces severe light scattering. In contrast, films of high optical quality resulted when we adapted an alternative hydrolytic method originally developed to form uniform coats of material on isolated colloids in solution.…”

Section: General Procedures For the De-o-acylationsmentioning

confidence: 99%

“…The possibility of swelling the columnar phases with pentaethyleneglycol is reminiscent of the effect of hydrocarbons on classical thermotropic columnar phases. [20] Given the fact that these discotic mesogens are chiral, as well as having some limited water solubility on account of their sugar-coated nature, they certainly merit further investigation.…”

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confidence: 99%