Structure of polymer networks in liquid crystals studied by 13C NMR

Riede, Andrea; Grande, S.; Hohmuth, A.; Weißflog, W.

doi:10.1080/026782997209513

Cited by 8 publications

(2 citation statements)

References 32 publications

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“…[30,36,37] Close to the transition into the nematic phase strong pretransitional ordering is observed by birefringence measurements [36] as well as order parameter determination by nuclear magnetic resonance (NMR). [38,39] Figure 4 depicts exemplary measurements of the residual birefringence as well as the pretransitional behavior on approaching the nematic phase from the isotropic liquid. [36] The birefringence of the polymer±liquid crystal system can be written as Dn = Dn P + Dn LC , where Dn P is the birefringence contribution of the polymer network and Dn LC that of the LC.…”

Section: Effect On Physical Parametersmentioning

confidence: 99%

Polymer Network-Stabilized Liquid Crystals

2000

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The fabrication and properties of polymer network±stabilized liquid crystals, formed by polymerization of a small amount of a bifunctional photoreactive monomer dissolved in a liquid-crystalline phase, are reviewed. The polymer network morphology is strongly related to preparation conditions such as monomer content, polymerization temperature, and ultraviolet (UV) curing conditions. The transfer of anisotropic liquid-crystalline order onto the network is discussed in detail. The electro-optical performance of network-stabilized nematics, cholesterics, and ferroelectric smectics is largely dependent on the morphology of the network, as will be demonstrated with an emphasis laid on polymer-stabilized cholesteric textures (PSCTs). A general correlation between polymerization conditions, network morphology, and electro-optical behavior will be outlined and aspects concerning applications discussed.

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Section: Effect On Physical Parametersmentioning

confidence: 99%

Polymer Network-Stabilized Liquid Crystals

2000

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“…The PVA polymer network influenced the behaviour of the surrounding liquid crystal and caused the nematic-isotropic transition temperature to drop by ~1.5 o C (i.e. a temperature drop from 35 o C to 32.5 o C) [9]. The liquid crystal in the PVA electrolyte forms a droplet-like structure embedded in the polymer matrix [10].…”

Section: Resultsmentioning

confidence: 99%

Conductivity Studies on the Effect of a Nematic Liquid Crystal on Polyvinyl Alcohol-Based Electrolytes

Zulkifli

Kamarudin

Mainal

et al. 2014

AMR

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Recently, a few studies have shown that the introduction of liquid crystals (LCs) in polymer electrolytes would lead to an increase in the chain mobility and the ionic conductivity. It is believed that this enhancement of the polymer electrolyte performance is greatly influenced by the order parameter of the liquid crystal in this system. In this study, a deuterated 4-pentyl-4-cyano-biphenyl (5CB-d2) nematic liquid crystal-doped polyvinyl alcohol (PVA) polymer electrolyte were prepared. The orientational order of the nematic liquid crystal is then investigated via the quadrupolar splittings of the deuterium Nuclear Magnetic Resonance (NMR) spectra. The quadrapolar splitting, which is directly related to the orientational order of the liquid crystal director, was measured and compared between the embedded 5CB-d2 in the PVA electrolyte to that of the pure 5CB-d2. The conductivity of a 5CB-d2 embedded in PVA reached up to 3.28x10-1 S/cm compare to that of without 5CB-d2 which is only 2.89x10-1S/cm. The presence of 5CB-d2 in the PVA polymer electrolyte improved the electrical conductivity of the mixture through an improved charge transfer mechanism, which improves its electrical properties, a criterion useful for a device that needs high conductivity.

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Structural and electro-optical investigations of the smectic phase of chlorine-substituted banana-shaped compounds

Pelzl¹

1999

Liquid Crystals

114

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Six members of a new homologous series of achiral banana-shaped molecules have been synthesized and studied by optical microscopy, di erential scanning calorimetry, NMR spectroscopy and X-ray di raction. According to X-ray di raction measurements on oriented samples, four homologues form an XB2 phase which exhibits antiferroelectric switching behaviour. From electro-optical studies the spontaneous polarization and the tilt angle could be measured. An orientational order parameter of 0.8 was determined by 13 C NMR and this is nearly independent of the temperature. NMR investigations also give information about the real conformation of the molecules in the XB2 phase. Dielectric measurements indicate that the rotation around the molecular long axis is clearly hindered because of the packing of the bent molecules within the smectic layers.

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Structure of polymer networks in liquid crystals studied by 13C NMR

Cited by 8 publications

References 32 publications

Polymer Network-Stabilized Liquid Crystals

Polymer Network-Stabilized Liquid Crystals

Conductivity Studies on the Effect of a Nematic Liquid Crystal on Polyvinyl Alcohol-Based Electrolytes

Structural and electro-optical investigations of the smectic phase of chlorine-substituted banana-shaped compounds

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