Chemistry and Applications of Liquid Crystals

Steinsträßer, Ralf; Pohl, L.

doi:10.1002/anie.197306171

Cited by 50 publications

(27 citation statements)

References 175 publications

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“…7). The tilt angle in SmC phase could not be ascertained owing to a first order transition [21], a transition that involved a discontinuity in entropy [22]. Hence, the layer spacing only reflects the conformation of the molecules during phase transition.…”

Section: X-ray Diffraction Study On Compounds 4 Andmentioning

confidence: 98%

Synthesis, mesomorphic properties and X-ray diffraction studies on 7-alkyloxy-3-(4-alkyloxyphenyl-4H-1-benzopyran-4-one: Crystal structure of 7-hexyloxy-3-(4-hexyloxyphenyl)-4H-1-benzopyran-4-one

Yeap

Yam

Dobrzyscky

et al. 2009

Journal of Molecular Structure

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Section: X-ray Diffraction Study On Compounds 4 Andmentioning

confidence: 98%

Synthesis, mesomorphic properties and X-ray diffraction studies on 7-alkyloxy-3-(4-alkyloxyphenyl-4H-1-benzopyran-4-one: Crystal structure of 7-hexyloxy-3-(4-hexyloxyphenyl)-4H-1-benzopyran-4-one

Yeap

Yam

Dobrzyscky

et al. 2009

Journal of Molecular Structure

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“…Nolle et al 27 and Porter and Johnson 28,29 believe that the pretransitional variations in specific volume occur on both sides of the transition. 6 for HBT and OBT respectively. /?…”

Section: Presents the Values Of B (L/v) • (Dv/dt)mentioning

confidence: 99%

“…Some parameters such as 5k , A, the adiabatic compressibility, the Rao number, and the van der Waals constant are also determined. Now a days the liquid crystalline state is recognized as a true state intermediate between the crystalline solid and the isotropic liquid state [1][2][3][4][5][6] . Generally, the mesophase-isotropic phase transitions are regarded as of first order though some recent measurements on this transition show some second order admixture.…”

mentioning

confidence: 99%

Notizen: Specific Volume Studies on Some Nematic Liquid Crystals

Bahadur

1975

Zeitschrift Für Naturforschung A

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The temperature variation of the specific volume of two nematic liquid crystals (HBT and OBT) has been observed in both the nematic and isotropic regions. A sudden jump is observed in the vicinity of the nematic-isotropic transition indicating a first order phase transition. Pretransitional effects are found to occur only on the nematic side of the transition. This accords with the Maier-Saupe theory. Some parameters such as 5k , A, the adiabatic compressibility, the Rao number, and the van der Waals constant are also determined. Now a days the liquid crystalline state is recognized as a true state intermediate between the crystalline solid and the isotropic liquid state [1][2][3][4][5][6] . Generally, the mesophase-isotropic phase transitions are regarded as of first order though some recent measurements on this transition show some second order admixture. Indeed, the cholestric and nematic liquid crystals exhibit the smallest first order transitions to the isotropic liquid known among pure compounds. In first order phase transitions a discontinuity or a steep change in specific volume is observed, while in second order transitions a point of inversion occurs (i. e. no discontinuity occurs in the first derivatives of Gibbs' free energy ' at the transition) .This paper, dealing with specific volume measurements of two nematic liquid crystals, (p-nhexyloxybenzylidene)-p-toluidine (HBT) and (p-noctyloxybenzylidene)-p-toluidine (OBT), is part of our systematic study on liquid crystals [8][9][10][11][12][13][14] .Both HBT and OBT were procured from M/S E. Merck (Germany) in pure form and were used as such. The transition temperatures were determined by means of a polarizing microscope and are listed below68.6°C 69.0°C 75.0°C Solid ^ Smectic ^ Nematic ^ Isotropic escThe specific volume was measured by means of a sensitive pycnometer u , which was placed in a regulated hot air oven (regulation better than + 0.1 ~C). The temperature variation of the volume of the pycnometer was also taken into account.The temperature dependences of the specific volume, the adiabatic compressibility (ß.id) and the Rao number (Rn) are shown in Figs. 1, 2 The specific volume increases linearly with temperature up to ~1 C below the nematic-isotropic transition, and again so in the isotropic region. A small but sudden discontinuity is observed which clearly indicates that the transition is of first order. The sudden increase of the specific volume with temperature near the nematic-isotropic transition is attributed to a sudden change from the ordered nematic to the disordered and less densely packed liquid state. From the Table 1 it can be observed that the thermal expansion coefficient [(l/u)" (di>/df)] is larger for the nematic than for the isotropic phase. This indicates that the increase of order with decreasing temperature is larger in the nematic than in isotropic phase.The breadths of the nematic-isotropic transitions are ~1.6°C and ~1.0°C in HBT and OBT respectively. The nematic-isotropic transition in our case is less sharp than i...

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“…On the other side, more attention has been directed toward the application of solid acids in organic synthesis because such reagents not only simplify purification processes but also help prevent release of reaction residues into the environment (9,10). Azo dyes are very important compounds in many branches of chemistry and are widely used as colorants in the textile industries (11), colorants for digital printing and photography (12), chiral receptors (13), liquid crystals (14), new glassy materials (15), chiral switches in photochemistry (16), dyes for drug, food, and cosmetic applications, in the biomedical field (17), and for molecular recognition (18). Therefore, due to the importance of the azo dyes, continuous efforts have been made to achieve simple and ecofriendly methodologies for the synthesis of these compounds.…”

Section: Introductionmentioning

confidence: 99%

Environmentally green approach to synthesize azo dyes based on 1-naphthol using nano BF₃·SiO₂under solvent-free conditions

Bamoniri

Mirjalili

Moshtael-Arani

2014

Green Chemistry Letters and Reviews

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A series of azo dyes were efficiently synthesized by mixing aromatic amines and NaNO 2 in the presence of nano silica supported boron trifluoride (nano BF 3 ·SiO 2 ) and then diazo coupling with 1-naphthol under solvent-free conditions at room temperature. The present methodology has proven to be simple, rapid, environmentally benign, green, and cost-effective compared with previous synthetic methods. Also, by using this procedure, aryl diazonium salts supported on nano BF 3 ·SiO 2 were very stable to be kept at room temperature for several months without any special conditions.

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Chemistry and Applications of Liquid Crystals

Cited by 50 publications

References 175 publications

Synthesis, mesomorphic properties and X-ray diffraction studies on 7-alkyloxy-3-(4-alkyloxyphenyl-4H-1-benzopyran-4-one: Crystal structure of 7-hexyloxy-3-(4-hexyloxyphenyl)-4H-1-benzopyran-4-one

Synthesis, mesomorphic properties and X-ray diffraction studies on 7-alkyloxy-3-(4-alkyloxyphenyl-4H-1-benzopyran-4-one: Crystal structure of 7-hexyloxy-3-(4-hexyloxyphenyl)-4H-1-benzopyran-4-one

Notizen: Specific Volume Studies on Some Nematic Liquid Crystals

Environmentally green approach to synthesize azo dyes based on 1-naphthol using nano BF₃·SiO₂under solvent-free conditions

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Chemistry and Applications of Liquid Crystals

Cited by 50 publications

References 175 publications

Synthesis, mesomorphic properties and X-ray diffraction studies on 7-alkyloxy-3-(4-alkyloxyphenyl-4H-1-benzopyran-4-one: Crystal structure of 7-hexyloxy-3-(4-hexyloxyphenyl)-4H-1-benzopyran-4-one

Synthesis, mesomorphic properties and X-ray diffraction studies on 7-alkyloxy-3-(4-alkyloxyphenyl-4H-1-benzopyran-4-one: Crystal structure of 7-hexyloxy-3-(4-hexyloxyphenyl)-4H-1-benzopyran-4-one

Notizen: Specific Volume Studies on Some Nematic Liquid Crystals

Environmentally green approach to synthesize azo dyes based on 1-naphthol using nano BF3·SiO2under solvent-free conditions

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Product

Resources

About

Environmentally green approach to synthesize azo dyes based on 1-naphthol using nano BF₃·SiO₂under solvent-free conditions