Temperature Dependence of Orientational Order in a Nematic Liquid Crystal at Constant Molar Volume

A molecular field theory for uniaxial nematic liquid crystals formed by non-cylindrically symmetric molecules

“…This problem can be avoided if the order parameter is measured at constant volume, for then the coefficients Ciq ~ should, to a good approximation, be independent of temperature. Such measurements are available for 4,4'-dimethoxyazoxybenzene [23] and the order .parameter Pz is plotted as a function of the reduced temperature in figure 3.…”

Advances in generalised van der Waals approaches for the isotropic–nematic fluid phase equilibria of thermotropic liquid crystals–an algebraic equation of state for attractive anisotropic particles with the Onsager trial function

“…The Maier-Saupe (MS) framework provided for the first time an approach capable of describing the temperature dependence of the nematic order in liquid crystals at the molecular level. Though not without its critics early on [7][8][9][10][11] , the MS theory has been widely adopted in the liquid-crystal community as a convenient model for the orientational order of thermotropic liquid crystals, most particularly in the analysis of experimental data [12][13][14] . The rich and varied phase behaviour exhibited by thermotropic mesogens (see the extensive compilation by Dunmur et al 15 for nematics alone) is clearly closely related to specific features of the attractive interactions be-F o r P e e r R e v i e w O n l y 2 tween the molecules (e.g., London dispersion forces, polarity/multipolarity, π − π interactions between aromatic cores, electrostatic/charge transfer interactions etc.).…”

Spatial Configuration and Thermodynamic Characteristics of Main‐Chain Liquid Crystals

“…Another interesting V-T relation, δ = −(∂ ln T/∂ ln V ) S , has been studied for various monomer LCs by several authors [McColl, 1972;McColl and Shih, 1972;Shirakawa et al, 1982Shirakawa et al, , 1983Sandmann, 1998;Würflinger and Sandmann, 2001]. In the MaierSaupe theory, only the attractive part of the intermolecular potential is considered, and the interactions between anisotropic molecules of different orientations are prescribed as a function of S 2 and 1/V 2 .…”

“…(7.1)]. The theory predicts δ = 2 for a given value of S. McColl et al [McColl, 1972;McColl and Shih, 1972] carried out NMR measurements on PAA under various pressures, finding δ = 4.0 for fixed values of S. They concluded that the enhancement of δ should be indicative of the contribution from the repulsive steric interactions. Since then, the pressure dependence of the NI phase transition has been studied to elucidate the slope δ = −(∂ ln T NI /∂ ln V N ), knowing that the order parameter S at the NI transition remains nearly invariant with pressure.…”