Equilibrium phase diagram of polystyrene and 8CB

Benmouna, Farida; Daoudi, A.; Roussel, Frédérick; Buisine, J. M.; Coqueret, Xavier; Maschke, Ulrich

doi:10.1002/(sici)1099-0488(19990801)37:15<1841::aid-polb8>3.0.co;2-3

Cited by 33 publications

(36 citation statements)

References 12 publications

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“…On the other hand, phase diagrams of mixtures of linear polystyrene (PS) and 8CB were analyzed using differential scanning calorimetry (DSC), POM, and LS 41,42) . These diagrams were constructed for PS samples with molecular weights spanning the range from 4 000 to 200 000 g/mol and possessing a narrow molecular weight distribution.…”

Section: Discussionmentioning

confidence: 99%

Equilibrium phase behavior of polymer and liquid crystal blends

Benmouna

Maschke²,

Coqueret³

et al. 2000

Macromol. Theory Simul.

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A theoretical framework describing the equilibrium phase behavior of polymers and liquid crystals is presented. Linear and crosslinked polymers are considered, and complexities found in the phase properties of systems involving crosslinked networks are highlighted. Effects of the rubber elasticity parameters in the elastic free energy are found to induce substantial distortions in the phase diagram. The Flory‐Huggins interaction parameter which governs the miscibility of the mixture in the isotropic state is assumed to be independent of the polymer architecture and modeled either by using a function of temperature only or temperature and composition. The thermodynamic description of the ordered domains is made according to the Maier‐Saupe theory for nematic order and its extension to include other ordering properties. In particular, the smectic‐A order is described according to the generalization of the Maier‐Saupe theory proposed by McMillan. In the presence of nematogens, the coupling leads to quite different phase properties. In the strong coupling limit, a wide single nematic phase is found. In the weak coupling, the miscibility gap is much wider. These mixtures are described with mean‐field theories of nematogen first developed by Brochard et al. and later extended by Kyu et al. This theoretical formalism has been applied successfully to analyze data obtained on several systems including linear and crosslinked polymer networks, smectic and nematic low molecular weight liquid crystals (LMWLC), and nematogen mixtures.

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Section: Discussionmentioning

confidence: 99%

Equilibrium phase behavior of polymer and liquid crystal blends

Benmouna

Maschke²,

Coqueret³

et al. 2000

Macromol. Theory Simul.

Self Cite

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“…The undissolved portion of the LC forms droplets. Knowing β and the amount of LC added to the polymer (x), we can calculate the phase-separated LC fraction (φ LC ) using [18][19][20] …”

Section: Maxwell-wagner-sillars Effectmentioning

confidence: 99%

Maxwell-Wagner-Sillars effects on the thermal-transport properties of polymer-dispersed liquid crystals

Kuriakose¹,

Longuemart²,

Depriester³

et al. 2014

Phys. Rev. E

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We present the depolarization field effects (Maxwell-Wagner-Sillars effect) for the thermal transport properties of polymer dispersed liquid crystal composites under a frequency-dependent electric field. The experiments were conducted on polystyrene/4-Cyano-4'-pentylbiphenyl (PS/5CB) PDLCs of 73 vol.% and 85 vol.% liquid crystal (LC) concentrations. A self-consistent field approximation model is used to deduce the electrical properties of polymer and LC materials as well as the threshold electric field. Electric field-varying (at constant frequency) experiments were also conducted to calculate the interfacial thermal resistance between the LC droplets and polymer matrix as well as to find the elastic constant of LCs in droplet form.

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“…An interesting finding, as can be seen in 1, is that the interaction parameter can be considered independent of the molecular weight of the LC (within statistical uncertainty), which is typically not the case for low molar mass species. Based upon the approach of Benmouna et al [16], the DSC data (shown in 4) was utilized to estimate the solubility limit of the liquid crystal in the polymer β (defined as the maximum amount of liquid crystal that can be dissolved in the polymer at T AI , expressed as a weight fraction) and the relative amount of liquid crystal in the liquid crystal-rich domains α (equal to the ratio of the weights of liquid crystal in the liquid crystal-rich domains over the total liq-…”

Section: Phase Diagramsmentioning

confidence: 99%

“…The values of β = 0.40 for PS/12CB and β = 0.42 for PS/10CB were determined. The fraction of liquid crystal in both polymer-and liquid crystal-rich domains can also be calculated from δ [16], under the assumption that the liquid crystal-rich phase is essentially pure:…”

Section: Phase Diagramsmentioning

confidence: 99%

Thermodynamics, Transition Dynamics, and Texturing in Polymer-Dispersed Liquid Crystals with Mesogens Exhibiting a Direct Isotropic/Smectic-A Transition

2009

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Experimental and modeling/simulation studies of phase equilibrium and growth morphologies of novel polymer-dispersed liquid crystal (PDLC) mixtures of PS (polystyrene) and liquid crystals that exhibit a direct isotropic/smectic-A (lamellar) mesophase transition were performed for PS/10CB (decylcyanobiphenyl) and PS/12CB (dodecyl-cyanobiphenyl). Partial phase diagrams were determined using polarized optical microscopy (POM) and differential scanning calorimetry (DSC) for different compositions of both materials, determining both phase separation (liquid/liquid demixing) and phase ordering (isotropic/smectic-A transition) temperatures. The Flory-Huggins theory of isotropic mixing and Maier-Saupe-McMillan theory for smectic-A liquid crystalline ordering were used to computationally determine phase diagrams for both systems, showing good agreement with the experimental results. In addition to thermodynamic observations, growth morphology relations were found depending on phase transition sequence, quench rate, and material composition. Three stages of liquid crystal-rich domain growth morphology were observed: spherical macroscale domain growth ("stage I"), highly anisotropic domain growth ("stage II"), and sub-micron spheroid domain growth ("stage III"). Nano-scale structure of spheroidal and spherocylindrical morphologies were then determined via two-dimensional simulation of a high-order Landau-de Gennes model. Morphologies observed during stage II growth are typical of direct isotropic/smectic-A phase transitions, such as highly anisotropic "batonnets" and filaments. These morphologies, which are found to be persistent in direct isotropic/smectic-A PDLCs, could provide new functionality and applications for these functional materials.

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Equilibrium phase diagram of polystyrene and 8CB

Cited by 33 publications

References 12 publications

Equilibrium phase behavior of polymer and liquid crystal blends

Equilibrium phase behavior of polymer and liquid crystal blends

Maxwell-Wagner-Sillars effects on the thermal-transport properties of polymer-dispersed liquid crystals

Thermodynamics, Transition Dynamics, and Texturing in Polymer-Dispersed Liquid Crystals with Mesogens Exhibiting a Direct Isotropic/Smectic-A Transition

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