Thermodynamic investigation of the thermotropic cubic mesogen, 1,2-bis(4- n -octyloxybenzoyl)hydrazine

Abstract

To cite this article: NOBUYUKI MORIMOTO (1999) Thermodynamic investigation of the thermotropic cubic mesogen, 1,2-bis(4-n -octyloxybenzoyl)hydrazine, Liquid Crystals, 26:2, 219-228,The molar heat capacity of the thermotropic cubic mesogen 1,2-bis(4-n-alkoxybenzoyl)hydrazine, BABH(8) for short, with a purity of 99.43 mol % has been precisely measured with an adiabatic calorimeter at temperatures between 14 and 480 K. The enthalpy and entropy gained at each phase transition across the phase sequence of [crystal(2) crystal(1) cubic mesophase SmC isotropic liquid] have been determined. The existence of a solid-to-solid phase transition with a fairly large entropy change seems to be necessary for the alkyl moieties attached to both sides of the molecule to play the role of`solvent' in the cubic mesophase. On the basis of curvature elasticity considerations, the small energy di erence between the cubic and SmC phases is favourably accounted for in terms of the jointed-rod micelles model. The reason for the immiscibility of BABH(8) with the cubic D mesogen, 4¾ -n-hexadecyloxy-3¾ -nitrobiphenyl-4-carboxylic acid is discussed in terms of the large di erence in their molecular size and of`structure breaking' arising from the admixture of heterogeneously hydrogen-bonded materials.

Thermodynamic Study of Phase Transitions in Lyotropic Liquid Crystals: Adiabatic Calorimetry on Nonionic Surfactant C12E6−Water System

“…However, no studies have so far been made to determine heat capacities accurately and to analyze these data in detail. We have conducted thermodynamic studies on thermotropic cubic mesogens by mainly utilizing adiabatic calorimetry. − As the present binary system involves a cubic mesophase at a certain concentration range, it is of great interest to compare the present lyotropic cubic mesophase with the optically isotropic mesophases in thermotropic liquid crystalline systems, e.g., the so-called D phase (CubD phase) in ANBC ,, and cubic phase in BABH. ,

1 Phase diagram of the C 12 E 6 −water system, based on the previous study by Clunie et al L α , lamellar phase; V I , normal bicontinuous cubic phase; H I , normal hexagonal phase, L 1 , aqueous surfactant solution; W, very dilute surfactant solution; S, solid surfactant. Arrows over the diagram indicate the concentrations of the samples in this study, the letter designations of which are described in Table .

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Aggregation structure of chiral cubic liquid crystals revealed by X-ray diffraction utilizing a new algorithm

“…It is emphasized that the chain disorder in most liquid crystals, including the present cases, 18,31,32 is comparable to that in the isotropic liquid phase and liquid alkanes. 48–50 The molecular conformation perpetually changes from time to time.…”

“…This paper utilizes the strategy to reveal the molecular aggregation in the chiral cubic phase of BABH( n ). Previous studies 12,31,32 have indicated that they are suitable targets for the algorithm. In the molecule, the hydrazine moiety (–HN–NH–) at the center has the highest electron density.…”

Thermodynamic Study of Phase Transitions in Lyotropic Systems: Adiabatic Calorimetry on Nonionic Surfactant C16E8−Water System

“…On the other hand, we have conducted thermodynamic studies on thermotropic cubic mesogens. − Recently, we proposed the quasi-binary (QB) picture of thermotropic liquid crystals and its application to the thermotropic cubic liquid crystals . The QB picture assumes that the long alkyl chains attached to the mesogenic molecules are highly disordered and serves as intramoleclar solvent (“self-solvent”) in liquid crystalline states.…”