Phase behavior of polymer/liquid crystal blends

Ahn, WonSool; Kim, C.Y.; Kim, H.; Kim, Sung Chul

doi:10.1021/ma00045a028

Cited by 82 publications

(60 citation statements)

References 12 publications

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“…There are three regions A, B, and C as reported for systems consisting of a polymer and an alkylcyanobiphenyl. [22][23][24][25] The region A is the isotropic solution state. Since 5CB is a poor solvent for PS, the liquidliquid phase separation occurs at the boundary between A and B.…”

Section: Methodsmentioning

confidence: 99%

“…It is known that 5CB is a liquid crystalline compound and 5CB/PS blends are expected to exhibit complicated phase behavior as observed in similar blends. [22][23][24][25] Since our interest is in the behavior in the isotropic mixture of 5CB and PS, we have to make sure that measurements are made on the isotropic blend. For this reason, the phase behavior of the PS/5CB is reported briefly and then the dielectric behavior of PS/5CB blends is reported in detail.…”

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confidence: 99%

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Dielectric Study of Dynamical Heterogeneity in Blends of Polystyrene and Low Mass Compounds

Hori

Urakawa

Adachi

2003

Polym J

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ABSTRACT:We investigated the dielectric relaxation in blends of 4-n-pentyl-4 -cyanobiphenyl (5CB) and polystyrene (PS) in order to examine the size effect of low mass molecules on the cooperativity of local dynamics. To obtain the dielectric data in the isotropic state, the phase diagram was produced. The temperature (T ) dependence of the dielectric loss factor ε of PS/5CB blends containing 20 to 30 wt% of 5CB exhibited a bimodal peak near the calorimetric glass transition temperature T g . The bimodal peak was resolved into two peaks termed α and β. The α process locates above T g and can be assigned to cooperative motions of the PS segments and the 5CB molecules. The β process is responsible to independent reorientation of the 5CB molecules in the glassy PS matrix. The α and β loss peaks tend to merge with increasing T . This behavior contrasts to the dielectric behavior of the PS/toluene system which exhibits loss peaks due to segmental motions of PS and rotation of the toluene molecules in well separated temperature regions. The toluene molecule has a size of ca. 1/3 of the 5CB molecule and does not move cooperatively with PS but the 5CB molecule does. From the intensity of the α and β peaks, the fraction of the 5CB molecules moving cooperatively with PS has been estimated to be 0.25 and 0.63 for the blends containing 30 and 20 wt% of 5CB, respectively.KEY WORDS Polystyrene / 4-n-Pentyl-4 -cyanobiphenyl / Dielectric Relaxation / Dynamical Heterogeneity / Cooperativity / Diluent / Segmental Motion / Dynamics of low molecular weight molecules dissolved in polymer matrices has been studied long by means of dielectric, 1-8 mechanical, 7, 8 NMR,6,7,9,10 light scattering, 7 fluorescence depolarization, 11 ESR,12 and thermal methods. 6, 13 Adachi et al. 4 and Yoshizaki et al. 1 reported the dielectric behaviors of the systems consisting of polystyrene (PS) and alkylbenzene such as toluene, ethylbenzene and butylbenzene. It was reported that the relaxation due to rotation of the solvent molecules (β process) and that due to segmental motions of PS (α process) occur separately in different temperature-frequency regions. 1, 4 Similar bimodal mobilities of components are reported for various systems consisting of large and small molecules. 5,6,9,10 This behavior is not in harmony with a generally believed view of cooperativity 14-18 of local motions in supercooled liquids near the glass transition temperature T g . For instance if the PS chains and the toluene molecules in the PS/toluene system move cooperatively, the splitting into the two different relaxation processes would not occur. Such behaviors have been reported even for miscible polymer blends and are called "dynamical heterogeneity". 19,20 However in those literatures referred above, the interest has been centered mostly on the spectral shapes of the relaxation processes and the relationship between the dynamical heterogeneity and the cooperativity has been scarcely investigated.What factors result in the dynamical heterogeneity in polymer/diluent systems? ...

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Dielectric Study of Dynamical Heterogeneity in Blends of Polystyrene and Low Mass Compounds

Hori

Urakawa

Adachi

2003

Polym J

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“…The phase diagrams of polymer-LC mixtures have been investigated extensively. Experimental studies of the phase diagrams have shown that a nematic isotropic transition of the LC occurs as well as a liquid-liquid phase transition between the polymer and the LC (Ahn et al, 1992;Benmouna et al, 2000;Dubault et al, 1980;Kronberg et al, 1978;Matsuyama et al, 2000;Shen & Kyu, 1995;Smith, 1993). Several authors predicted the phase diagrams theoretically by combining Flory-Huggins theory for isotropic mixing of two components with Malser-Saupe theory for nematic interactions (Holyst & Schick, 1992;Matsuyama & Kato, 1996).…”

Section: Introductionmentioning

confidence: 99%

Concentration fluctuations induced by orientation fluctuations in polybutadiene–4-cyano-4'-n-octylbiphenyl mixtures

et al. 2007

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The changes in concentration fluctuations of polymer-liquid crystal (LC) binary mixtures with temperature were investigated by small-angle X-ray scattering in their one-phase region and in the isotropic state of the LC. The concentration fluctuations consist of two modes: an OZD mode expressed by the OrnsteinZernike-Debye equation with a correlation length and a DB mode expressed by the Debye-Buche equation with a correlation length l. The temperature dependence of the OZD mode exhibits critical phenomena similar to common binary mixtures. Under the condition where the LC molecules are oriented by an electric field, the OZD mode is insensitive to the orientation while the DB mode is enhanced perpendicular to the orientation direction. These results indicate that the DB mode is induced by the orientation of the LC molecules.

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“…Blends of low molecular-weight liquid crystals (LC) with polymers have been extensively studied (1)(2)(3)(4)(5), because such mixtures are expected to be useful as materials for electro-optical applications. Many studies have been reported on the phase behavior of blends of LC with flexible-chain polymers, such as poly(ethylene oxide) (3)(4)(5), polystyrene (3)(4)(5), and poly(methyl methacrylate) ( 5 ).…”

Section: Introductionmentioning

confidence: 99%

“…Many studies have been reported on the phase behavior of blends of LC with flexible-chain polymers, such as poly(ethylene oxide) (3)(4)(5), polystyrene (3)(4)(5), and poly(methyl methacrylate) ( 5 ). Some of the polymers were shown to be partially miscible with low molecular-weight LC materials.…”

Section: Introductionmentioning

confidence: 99%

Morphological Studies on Polymer/Liquid Crystal Blend.

Kaito

Rodrigues

1994

Sen-i Gakkaishi

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The morphology of blends of a low molecular-weight liquid crystal (LC) with poly (caprolactone) (PCL) was studied with differential scanning calorimetry, polarized optical microscopy, and scanning electron microscopy. The crystallization of PCL resulted in the crystalline domains in the blend, and their morphology was dependent on the composition. The changes in morphology during crystallization and melting processes were also examined by optical microscopy.

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Phase behavior of polymer/liquid crystal blends

Cited by 82 publications

References 12 publications

Dielectric Study of Dynamical Heterogeneity in Blends of Polystyrene and Low Mass Compounds

Dielectric Study of Dynamical Heterogeneity in Blends of Polystyrene and Low Mass Compounds

Concentration fluctuations induced by orientation fluctuations in polybutadiene–4-cyano-4'-n-octylbiphenyl mixtures

Morphological Studies on Polymer/Liquid Crystal Blend.

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