Polymer network structure and electro-optic performance of polymer stabilized cholesteric textures II. The effect of UV curing conditions

Dierking, Ingo; Kosbar, Laura L.; Lowe, A. C.; Held, G. A.

doi:10.1080/026782998207217

Cited by 67 publications

(37 citation statements)

References 5 publications

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“…In contrast, the time of UV irradiation has a drastic effect on the network morphology, especially during the first hour of exposure. [56] From our electro-optical and SEM investigations we conclude that the polymerization process is completed after approximately 30±60 min. A strongly decreasing network void size is observed for increasing time of irradiation, indicating that the polymerization process is proceeding with time.…”

Section: Polymerization Conditions and Network Morphologymentioning

confidence: 65%

“…Exemplary data of the dependence of some important electro-optical parameters on curing temperature are summarized in Figure 13. UV Conditions: [34,56] The UV conditions of the photopolymerization process can be varied either by variation of I. Dierking/Polymer Network±Stabilized Liquid Crystals the UV intensity or the time of UV irradiation. Variation of the UV intensity in the range between 0.01 and 10 mW cm ±2 does not have a pronounced effect on the network morphology, only slightly increasing the network void size for increasing intensity.…”

Section: Polymerization Conditions and Network Morphologymentioning

confidence: 99%

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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: Polymerization Conditions and Network Morphologymentioning

confidence: 65%

Section: Polymerization Conditions and Network Morphologymentioning

confidence: 99%

Polymer Network-Stabilized Liquid Crystals

2000

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“…Because of the high miscibility between the polymer and the liquid crystal, polymerization-induced phase separation is suppressed, and a porous polymer matrix possessing helical molecular orientation is obtained. The pores in the polymer matrix is typically on the order of several 10-100 nm, which is significantly smaller compared to PSChLCs, which have LC domains sizes of typically 400-500 nm [13,14]. Since the nano-pores are much smaller than the visible light wavelength, they do not give rise to scattering nor deform the helical structure, but affect the effective refractive index instead.…”

Section: Introductionmentioning

confidence: 99%

Pitch-Length Independent Threshold Voltage of Polymer/Cholesteric Liquid Crystal Nano-Composites

et al. 2015

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Polymer/cholesteric liquid crystal (ChLC) nano-composites consisting of mesogenic monomers and LCs have nano-sized LC domains dispersed in an anisotropic polymer matrix. They exhibit characteristics not observed in conventional ChLCs, such as sub-millisecond and "deformation-free" electro-optic tuning of the selective reflection band; however, their driving voltage is high compared to conventional ChLCs, and is an issue that needs to be solved for the practical use. Here, we investigate the helical pitch dependence of threshold voltage in polymer/ChLC nano-composites. Five samples with different helical pitches were prepared and their electro-optic characteristics were compared before and after photopolymerization. Although the threshold voltage of the unpolymerized samples were inversely proportional to its helical pitch, the threshold voltage of the polymerized samples showed no dependence on the helical pitch. These results are explained to be a consequence of the driving mechanism of the polymer/ChLC nano-composite, in which electro-optic switching is achieved as a consequence of the nano-confined LC molecules reorienting along the electric field, instead of the helical structure becoming unwound. The threshold voltage is independent of pitch length because the pore sizes are similar in all samples.

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“…For example, polymer-dispersed LCs (PDLCs), with a high monomer content [1][2] and polymer-stabilized cholesteric textures (PSCTs), with a low monomer content, are the mostly widely used light shutters that require no polarizer [3][4][5][6][7][8][9][10][11][12]. They can be electrically switched between the strongly scattering state and the highly transparent state.…”

Section: Introductionmentioning

confidence: 99%

Influence of Curing Frequency on the Morphology and the Electro-Optical Property of Polymer-Stabilized Cholesteric Textures

Zhang

Wang

et al. 2013

Molecular Crystals and Liquid Crystals

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The effect of curing frequency on the morphology of polymer networks and the electrooptical property of normal-mode polymer-stabilized cholesteric textures (PSCTs) has been investigated. The scanning electron microscopy indicates that the shape of polymer networks transforms from honeycomb-like to fiber-like due to the increased solubility of the monomer at higher curing frequencies. The PSCTs cured at lower frequencies with sufficiently large network voids show a two-stage reorientation process that correlates with two kinds of cholesteric liquid crystal (LC) under different environments. The threshold voltage decreases as the curing frequency increases from 1 Hz to 10,000 Hz, while the field-off response time increases.

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Polymer network structure and electro-optic performance of polymer stabilized cholesteric textures II. The effect of UV curing conditions

Cited by 67 publications

References 5 publications

Polymer Network-Stabilized Liquid Crystals

Polymer Network-Stabilized Liquid Crystals

Pitch-Length Independent Threshold Voltage of Polymer/Cholesteric Liquid Crystal Nano-Composites

Influence of Curing Frequency on the Morphology and the Electro-Optical Property of Polymer-Stabilized Cholesteric Textures

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