Thermodynamic Properties of a Series of P-N-Alkyl-P’,-Cyanobiphenyls

Cox, Robert J.; Barrall, Edward M.; Doelman, A.; Clecak, Nicholas J.; Logan, J. A.; Diller, R. D.; Gregges, A. R.

doi:10.1007/978-1-4615-6443-0_2

Cited by 8 publications

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“…3, is equal to 1.785 J/(mol K) and 1.538 J/(mol K), which gives for the latent heat the values of 466 J/mol and 541 J/mol for 6CB + 3CyP5 and 7CP mixtures, respectively. The values of ∆H obtained in our experiment, although very approximate, are situated within the limits of the values obtained with the calorimetric methods for the nematic to the isotropic phase transition of pure 6CB (from 896 J/mol [10] to 293 J/mol [11]). Figures 4a and 5a present temperature dependences of the shear viscosity of the solutions studied.…”

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confidence: 85%

Viscous Behavior of Binary Mixtures of Mesogenic Solvent/Non-Mesogenic Solute

2006

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The paper presents results of the shear viscosity measurements performed on diluted binary mixtures of mesogenic solvent n-hexylcyanobiphenyl (C 6 H 13 PhPhC≡N, 6CB) and two non-mesogenic admixtures: (i) n-heptylcyanophenyl (C7H15PhC≡N, 7CP), composed of the molecules of the same polarity as the solvent molecules but of a slightly shorter length, and (ii) 4-n-propylcyclohexyl-4'-n-pentylphenyl (C 3 H 7 CyHxPhC 5 H 11 , 3CyP5), composed of the non-polar molecules but of a length very close to that of the mesomorphic solvent molecules. The experiment showed that the concentrational depression of the clearing temperature and the temperature extent of the isotropic + nematic (I + N) two-phase region in the mixtures are significantly smaller, i.e. the nematic phase is more thermodynamically stable, when the admixture molecular length is compatible to that of the mesogenic solvent, regardless of the polarity of the admixture molecules. The activation energy for freely flowing mixtures in the isotropic, nematic, and two-phase I + N regions was determined and discussed.

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Section: Resultssupporting

confidence: 85%

Viscous Behavior of Binary Mixtures of Mesogenic Solvent/Non-Mesogenic Solute

2006

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“…The entropy jump ∆S 0 NI , estimated from the data presented in the figure, is equal to 1.66 J/(mol K), which gives for the latent heat (∆H 0 NI ) T NI S 0 NI ), the value of about 0.5 kJ/mol. This value is situated within the limits of those obtained with the calorimetric methods for the I-N transition in pure 6CB (from 0.3 kJ/mol 6 to 0.9 kJ/mol 14 ). So, the presented results clearly show that an analysis of the phase diagram, which, in principle can be obtained in a simple way, can lead to quite important thermodynamic conclusions concerning the nature of the I-N phase transition.…”

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confidence: 84%

The Entropy Effects in Binary Mixtures of Polar Mesogenic Solvent/Nonpolar Solute

2008

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The paper concerns two aspects of the entropy in mesogenic systems: (i) the entropy jump (Delta S (0) NI) at the phase transition from the isotropic liquid (I) to the nematic liquid crystalline state (N), and (ii) the entropy increment (Delta S) caused by the ordering action of the probing electric field applied to the dipolar system. The system studied are the mixtures of strongly polar mesogenic solvent n-hexylcyanobiphenyl (C 6H 13PhPhCN, 6CB) and the nonpolar nonmesogenic admixture 4-ethylcyclohexyl-4'- n-nonylphenyl (C 2H 5CyHxPhC 9H 19, 2CyPh9). The entropy jump at the I-N phase transition in pure 6CB [Delta S (0) NI= 1.52 J/(mol K)] was evaluated from the analysis of the phase diagram of the mixture 6CB + 2CyPh9 with use of the Landau-Lifshitz theory; the resulting value of the transition enthalpy (Delta H (0) NI = T NIDelta S (0) NI = 0.50 kJ/mol) agrees well to that obtained with the calorimetric methods. The field-induced entropy increment (Delta S) was calculated, at the given temperature, from the static dielectric permittivity derivative value (depsilon s/d T), with use of the Fröhlich theory. The singularities in dependence of the entropy increment on the temperature and on the mixtures composition are discussed in terms of the prenematic molecular self-organization extent in mesogenic liquids of different density of dipoles.

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Landolt-Börnstein - Group IV Physical Chemistry

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Thermodynamic Properties of a Series of P-N-Alkyl-P’,-Cyanobiphenyls

Cited by 8 publications

References 9 publications

Viscous Behavior of Binary Mixtures of Mesogenic Solvent/Non-Mesogenic Solute

Viscous Behavior of Binary Mixtures of Mesogenic Solvent/Non-Mesogenic Solute

The Entropy Effects in Binary Mixtures of Polar Mesogenic Solvent/Nonpolar Solute

References for 1 and 2

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