Phase diagrams of a binary smectic-A mixture

Chiu, Hao‐Wen; Kyu, Thein

doi:10.1063/1.474926

Cited by 28 publications

(33 citation statements)

References 14 publications

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“…Mean field theories can also be extended to the phase behavior of smectic A liquid crystal and flexible polymer blends [63,[70][71][72][73][74] where q is the angle between the long axis of the nematogens and the director, = , is the average distance between smectic layers, and ; cosq is the distribution function of nematogens. The parameter c shows the dimensionless interaction for a smectic A phase.…”

Section: Smectic-nematic-isotropic Phase Separationsmentioning

confidence: 99%

“…Even in case of a flexible polymer, it may be possible that the partial orientational ordering of the polymer in a nematic solvent can give rise to an induced-nematic phase [89]. It has been recognized that a smectic phase can be induced in a nematic liquid crystal mixture by strong mesogenic interactions [71,76,90]. Phase separations strongly depend on the conformations of a polymer.…”

Section: Conformation Of a Polymer Dissolved In A Liquid Crystalline mentioning

confidence: 99%

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Thermodynamics of Flexible and Rigid Rod Polymer Blends

Matsuyama

2010

Encyclopedia of Polymer Blends

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Binary mixtures of a flexible polymer and a low molecular weight liquid crystalline molecule, or a rigid rod-like molecule, are of interest because of their important technological applications in high modulus fibers, nonlinear optics, and electro optical devices. These blends are basic materials for recent new technologies of liquid crystal displays [1,2]. The performances of these systems are closely related to phase separations and conformations of polymer chains dissolved in a liquid crystalline phase. One of the main problems is to examine the location of various phases such as isotropic, nematic, and smectic phases, depending on temperature and concentra tion. To understand the thermodynamics and thermal instability of these blends, it is important to consider the co-occurrences between liquid crystalline ordering and phase separations.Generally, polymer chains exhibit a variety of flexibility, from flexible to rigid rodlike polymers. Polymer blends containing a liquid crystalline ordering have received considerable attention. The volume of literature on the theories and experiments of liquid crystallinity in polymer blends is now very extensive. There are many theoretical models for liquid crystalline polymers, such as the Flory lattice model [3][4][5][6][7][8], wormlike chain model [9][10][11], and Onsager virial theory [12] for rigid rods. An example of a recent review of liquid crystalline polymers is the text book of Donald and Windle [13].In this chapter we introduce the thermodynamics, or phase behavior, of binary mixtures of a flexible polymer and a rigid rod-like molecule. Here the flexible polymer means that liquid crystalline ordering does not occur in the constituent pure polymer. We first describe the fundamentals of a nematic phase, based on the Onsager theory for a rigid rod, where the entropy-induced nematic ordering is discussed. This will be the basis of the following sections. In Section 2.3, we focus on the phase separations of mixtures of a flexible polymer and a rigid rod-like molecule, or a low molecular weight liquid crystalline molecule, in a thermal equilibrium state. We introduce recent theoretical models to describe phase behavior, combining the Flory-Huggins Edited by Avraam I. Isayev

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Section: Smectic-nematic-isotropic Phase Separationsmentioning

confidence: 99%

Section: Conformation Of a Polymer Dissolved In A Liquid Crystalline mentioning

confidence: 99%

Thermodynamics of Flexible and Rigid Rod Polymer Blends

Matsuyama

2010

Encyclopedia of Polymer Blends

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“…Liu and Fredrickson 6 developed a rigorous statistical mechanical description of the free energy of liquid crystalline polymer blends involving nematic ordering. Kyu and co-workers [7][8][9][10][11] further expanded the polymer/ nematic theory to the polymer/smectic A and the binary smectic-A system by incorporating the McMillan free energy of the nematic-smectic-A transition. The resulting Flory-Huggins Maier-Saupe-McMillan ͑FH-MSM͒ theory is capable of elucidating most phase diagrams of a polymersmectic A or binary smectic-A mixture.…”

Section: Introductionmentioning

confidence: 99%

“…We have combined the MSM free energy for the nematic and smectic-A transition with the Flory-Huggins free energy of liquidliquid mixing. Using the methodologies developed for earlier LC mixtures, 9,11 the combined free energy is then minimized at each temperature and composition with respect to all order parameters. The equilibrium coexistence points are then calculated self-consistently to compare with the reported experimental phase diagrams.…”

Section: Introductionmentioning

confidence: 99%

Crystal-liquid crystal binary phase diagrams

Dayal

Matkar

Kyu

2006

The Journal of Chemical Physics

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We propose a new theoretical scheme for the binary phase diagrams of crystal-liquid crystal mixtures by a combination of a phase field model of solidification, the Flory-Huggins theory for liquid-liquid mixing and Maier-Saupe-McMillan (FH-MSM) model for nematic and smectic liquid crystal orderings. The phase field theory describes the crystal phase transition of anisotropic organic crystal and/or side chain liquid crystalline polymer crystals while the FH-MSM model explains isotropic, nematic and smectic-A phase transitions. Self-consistent calculations reveal several possible phase diagram topologies of the binary crystal-liquid crystal mixtures. The calculated phase diagrams were found to accord well to the reported experimental results.

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“…They were able to obtain a variety of phase diagrams even in the case where the transition temperatures T NI 1 and T NI 2 of the pure constituents are nearly the same. Chiu, Kyu, and co‐workers addressed the equilibrium phase properties of polymer/solvent nematic mixtures,2 smectic‐A mixtures,3 nematic SCLC and smectic‐A low‐molecular‐weight liquid crystals (LMWLC),4 and nematic and smectic‐A mixtures 5. In ref.…”

Section: Introductionmentioning

confidence: 99%

On the phase equilibria of nematic mixtures

Benmouna

Maschke²,

Coqueret³

et al. 2000

J. Polym. Sci. B Polym. Phys.

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The theory of Brochard et al. for mixtures of nematogens is applied to the case of crosslinked polymers with side chain liquid crystals and low‐ molecular‐weight liquid crystals. Phase equilibria of those mixtures are analyzed by allowing the Flory–Huggins interaction parameter for isotropic mixture and the rubber elasticity parameters of the elastic network to be functions of the polymer volume fraction. A wide range of crosslinking density is covered showing a strong influence on the phase behavior of such compounds. The clearing temperature of nematic‐isotropic transition of each nematogen is different and the cross‐nematic interaction parameter is a geometric average of the parameters for pure nematogens. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 478–485, 2000

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Phase diagrams of a binary smectic-A mixture

Cited by 28 publications

References 14 publications

Thermodynamics of Flexible and Rigid Rod Polymer Blends

Thermodynamics of Flexible and Rigid Rod Polymer Blends

Crystal-liquid crystal binary phase diagrams

On the phase equilibria of nematic mixtures

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