A statistical theory of liquid crystalline mixtures: phase separation

1976 ◽  
Vol 352 (1668) ◽  
pp. 41-56 ◽  
Keyword(s):  
Liquid Crystal ◽  
Phase Separation ◽  
Liquid Crystalline ◽  
Experimental Studies ◽  
Phase Region ◽  
Crystal Formation ◽  
Two Phase ◽  
First Order ◽  
Repulsive Forces

The molecular field theory of multicomponent liquid crystalline mixtures, developed by Humphries, James & Luckhurst, has been extended to investigate the possibility of phase separation in binary mixtures of rods and spheres. This extension indicates that the addition of a spherical solute to a liquid crystal depresses the transition from the isotropic to the nematic phase. The solute induced phase transition is first order, although the nematic and isotropic phases are found to be separated by a two-phase region consisting of both nematic and isotropic phases. These qualitative conclusions of the theory are in complete accord with experiment and there is also reasonable agreement with certain quantitative predictions. The same problem has been tackled using a lattice model with purely repulsive anisotropic interactions; this theory would appear to be marginally less successful than our own which is based on a weaker anisotropic potential. Consequently it is not possible to use experimental studies of phase separation in binary liquid crystal mixtures to demonstrate the rôle of repulsive forces in liquid crystal formation.

Solution Properties and Phase Behavior of Ammonium Hexylene Octyl Succinate in Water and Water-Oil System

1970 ◽  
Vol 3 (1) ◽  
Author(s):  
Md. Hamidul Kabir ◽  
Ravshan Makhkamov ◽  
Shaila Kabir
Keyword(s):  
Critical Micelle Concentration ◽  
Phase Behavior ◽  
Liquid Crystalline ◽  
Carbon Number ◽  
Phase Region ◽  
Solution Properties ◽  
Middle Phase ◽  
Two Phase ◽  
Lamellar Liquid Crystal ◽  
Drug Ingredient

The solution properties and phase behavior of ammonium hexylene octyl succinate (HOS) was investigated in water and water-oil system. The critical micelle concentration (CMC) of HOS is lower than that of anionic surfactants having same carbon number in the lipophilic part. The phase diagrams of a water/ HOS system and water/ HOS/ C10EO8/ dodecane system were also constructed. Above critical micelle concentration, the surfactant forms a normal micellar solution (Wm) at a low surfactant concentration whereas a lamellar liquid crystalline phase (La) dominates over a wide region through the formation of a two-phase region (La+W) in the binary system. The lamellar phase is arranged in the form of a biocompatible vesicle which is very significant for the drug delivery system. The surfactant tends to be hydrophilic when it is mixed with C10EO8 and a middle-phase microemulsion (D) is appeared in the water-surfactant-dodecane system where both the water and oil soluble drug ingredient can be incorporated in the form of a dispersion. Hence, mixing can tune the hydrophile-lipophile properties of the surfactant. Key words: Ammonium hexylene octyl succinate, mixed surfactant, lamellar liquid crystal, middle-phase microemulsion. Dhaka Univ. J. Pharm. Sci. Vol.3(1-2) 2004 The full text is of this article is available at the Dhaka Univ. J. Pharm. Sci. website

scholarly journals Relationship between Liquid Crystal Formation and Conformations of Twin Components in Liquid Crystalline Binary Systems.

1999 ◽  
Vol 56 (6) ◽  
pp. 341-349 ◽  
Author(s):  
Seiji UJIIE ◽  
Hiroko UCHINO ◽  
Kazuyoshi IIMURA ◽  
Moriyuki SATO
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Binary Systems ◽  
Crystal Formation

scholarly journals Monoclinic–orthorhombic first-order phase transition in K2ZnSi5O12 leucite analogue; transition mechanism and spontaneous strain analysis.

2021 ◽  
pp. 1-20
Author(s):  
Anthony M.T. Bell ◽  
Francis Clegg ◽  
Christopher M.B. Henderson
Keyword(s):  
Phase Transition ◽  
Strain Analysis ◽  
Phase Region ◽  
Martensitic Transition ◽  
Two Phase ◽  
Spontaneous Strain ◽  
First Order ◽  
Transition Mechanism ◽  
First Order Phase Transition ◽  
Increasing Temperature

Abstract Hydrothermally synthesised K2ZnSi5O12 has a polymerised framework structure with the same topology as leucite (KAlSi2O6, tetragonal I41/a), which has two tetrahedrally coordinated Al3+ cations replaced by Zn2+ and Si4+. At 293 K it has a cation-ordered framework P21/c monoclinic structure with lattice parameters a = 13.1773(2) Å, b = 13.6106(2) Å, c = 13.0248(2) Å and β = 91.6981(9)°. This structure is isostructural with K2MgSi5O12, the first cation-ordered leucite analogue characterised. With increasing temperature, the P21/c structure transforms reversibly to cation-ordered framework orthorhombic Pbca. This transition takes place over the temperature range 848−863 K where both phases coexist; there is an ~1.2% increase in unit cell volume between 843 K (P21/c) and 868 K (Pbca), characteristic of a first-order, displacive, ferroelastic phase transition. Spontaneous strain analysis defines the symmetry- and non-symmetry related changes and shows that the mechanism is weakly first order; the two-phase region is consistent with the mechanism being a strain-related martensitic transition.

New liquid crystal formation induced by nanoscale phase separation composed of bent-core liquid crystal and rod-like cholesteric liquid crystal mixtures

Soft Matter ◽  
2021 ◽  
Author(s):  
Yoichi Takanishi
Keyword(s):  
Liquid Crystal ◽  
Phase Separation ◽  
Liquid Crystals ◽  
Small Angle ◽  
Cholesteric Liquid Crystal ◽  
Crystal Formation ◽  
Nano Structure ◽  
X Ray ◽  
Nanoscale Phase Separation ◽  
X Ray Scattering

Herein, the local nano-structure in mixtures of cholesteric liquid crystals and a bent-core molecule was analyzed via the small-angle X-ray scattering.

Two-Phase Microstructures Formed by Phase-Separation of Coherent Precipitates in Elastically Constrained Alloy Systems

2010 ◽  
Vol 638-642 ◽  
pp. 2215-2220 ◽  
Author(s):  
Minoru Doi
Keyword(s):  
Free Energy ◽  
Phase Separation ◽  
Surface Energy ◽  
Phase Region ◽  
Precipitate Phase ◽  
Two Phase ◽  
Phase Separations ◽  
Chemical Free Energy ◽  
Elastic Constraint ◽  
Alloy Systems

Coherent two-phase microstructures consisting of ordered precipitate and disordered matrix phases sometimes exhibit a phase-separation, which brings the split and/or the decelerated coarsening of precipitates. When the coherent two-phase microstructure of A1+L12 (+’) in Ni-base alloys are aged inside the two-phase region of A1+L12 , the L12 precipitate sometimes exhibit a phase-separation and A1 phase newly appears and grows in each L12 precipitate. Phase-separations of the same type to the above also take place due to ageing of coherent two-phase microstructures of A2+D03 and A2+B2 in Fe-base alloys: D03 and B2 precipitates sometimes exhibit phase-separations and A2 phase newly appears and grows in both precipitates. These types of phase-separation take place under the influence of chemical free energy. In the course of further ageing, the new disordered phases of A1 and A2 change their morphology in various ways depending on the elastic constraint: i.e. the morphology of new A1 or A2 phase is influenced by the elastic energies and the surface energy.

Modification of Interfacial Properties of Polymer Blends with Diblock Copolymer

1996 ◽  
Vol 461 ◽  
Author(s):  
S. Kim ◽  
C. C. Han
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Polymer Blends ◽  
Diblock Copolymer ◽  
Diblock Copolymers ◽  
Phase Region ◽  
Domain Growth ◽  
Two Phase ◽  
Phase Separation Kinetics ◽  
Styrene Butadiene

ABSTRACTThe effect of diblock copolymer on the phase-separation process of polymer blends has been investigated by using light scattering and optical microscopic observations. To quench the system into the two phase region, a shear-jump technique is employed instead of the conventional temperature-jump technique. The samples studied are blends of low-molecular-weight polystyrene and polybutadiene with and without added styrene-butadiene block copolymer as a compatibilizer. It was observed that the addition of diblock copolymers could accelerate the phase separation kinetics depending on the shear history. As the concentration of diblock copolymer increases, the distribution of domain sizes becomes narrower and the growth rate slows down. The extent of slowing-down depends on the molecular weight and concentration of the copolymer. The time dependence of domain growth is clearly observed with optical microscopy.

Precipitation in Cu-Bearing GOES at the Start of Primary Recrystallization

2017 ◽  
Vol 891 ◽  
pp. 131-136
Author(s):  
Anastasia Volodarskaja ◽  
Jan Holešinský ◽  
Šárka Miklušova ◽  
Vlastimil Vodárek
Keyword(s):  
Cold Rolling ◽  
Experimental Studies ◽  
Primary Recrystallization ◽  
Minor Phase ◽  
Two Phase ◽  
Equilibrium Phases ◽  
Cu Dissolution ◽  
Phase Evaluation ◽  
Copper Effect

The role of copper additions to GOES has not been fully understood yet. Several mechanisms have been proposed: stabilization of austenite during hot rolling in two phase α+γ region, precipitation of ε - Cu, dissolution and re-precipitation of Cu-bearing sulfides, segregation of copper at grain boundaries and support of deformation by twinning and shear during cold rolling.This paper deals with minor phase evaluation in Cu–bearing GOES after following manufacturing steps: a) the first cold rolling and decarburization annealing at 820 °C, b) the second cold rolling followed by a slow laboratory heating to the temperature of primary recrystallization (620°C). Microstructure analysis was carried out using EBSD and TEM techniques. Results of experimental studies were compared with Thermocalc predictions of the copper effect on equilibrium phases in GOES.

Phase-Separations of Coherent Precipitates of Ordered Phases in Elastically Constrained Alloys

2006 ◽  
Vol 980 ◽  
Author(s):  
Minoru Doi ◽  
Hiroshi Kumagai ◽  
Kanako Nakashima ◽  
Takao Kozakai
Keyword(s):  
Phase Separation ◽  
Phase Region ◽  
Point Of View ◽  
Two Phase ◽  
Phase Separations ◽  
Transmission Electron ◽  
Ordered Phases ◽  
Chemical Free Energy ◽  
Fe Alloys ◽  
Means Of Transmission

AbstractPhase-separations of coherent precipitates of ordered phases were investigated by means of transmission electron microscopy (TEM) and the theoretical analysis from a thermodynamic point of view. When the two-phase microstructures of A1+L12 in elastically constrained Ni-Al-Ti and Ni-Si-Fe alloys are isothermally heated inside the two-phase region of A1+L12 , coherent L12 precipitate particles sometimes exhibit a phase-separation and A1 phase newly appears and grows in L12 particles. Phase-separations of the same type as the above are also observed in coherent two-phase microstructures of A2+D03 and A2+B2 in elastically constrained Fe-Si-V and Fe-Al-Ni alloys respectively: coherent D03 or B2 precipitates exhibit a phase-separation and A2 phase newly appears and grows in both precipitates. Such phase-separation is realized under the influence of chemical free energy and elastic energies.

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