Probing the Mesoscopic Chemical and Physical Properties of Polymer-Dispersed Liquid Crystals

Higgins, Daniel A.

doi:10.1002/(sici)1521-4095(200002)12:4<251::aid-adma251>3.0.co;2-4

Cited by 152 publications

(110 citation statements)

References 84 publications

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“…[1][2][3][4][5] The phase behavior and swelling properties of selected, well-defined polymer networks in two low molecular weight nematic liquid crystals (LCs) are discussed. A survey of the literature reveals a large number of theoretical and experimental reports mainly based on the swelling behavior of isotropic polymer networks in isotropic solvents (see ref.…”

Section: Introductionmentioning

confidence: 99%

Phase Behavior of Poly(butyl acrylate) Networks in Nematic Liquid Crystal Solvents

Vendamme

Bouchaour

Pakuła

et al. 2004

Macro Materials & Eng

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Summary: This paper reports the phase behavior of photochemically crosslinked poly(butyl acrylate) networks in nematic liquid crystal (LC) solvents. The swelling properties are studied as a function of temperature for two low molecular weight nematic LCs, 4‐cyano‐4′‐pentylbiphenyl (5CB) and the eutectic mixture of cyanoparaphenylenes (E7). Chemically crosslinked polymer networks were formed by the UV radiation of initial solutions of the reactive monomer, butyl acrylate, a crosslinker (hexanediol diacrylate), and a photoinitiator. To obtain different network densities, the ratio of butyl acrylate to hexanediol diacrylate was varied prior to polymerization/crosslinking reactions. Immersion in an excess of the LC solvent allowed for the measurement of size increase by polarized optical microscopy in terms of temperature. Length, width, and diagonal ratios were calculated considering swollen to dry network states of the samples. In general, swelling leads to an increase in the network size by increasing the temperature with a significant dependence on the degree of crosslinking. A large shift in the swelling ratio was found in the vicinity of the nematic to isotropic transition temperatures of the LCs. magnified image

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Section: Introductionmentioning

confidence: 99%

Phase Behavior of Poly(butyl acrylate) Networks in Nematic Liquid Crystal Solvents

Vendamme

Bouchaour

Pakuła

et al. 2004

Macro Materials & Eng

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“…As is well-known, [38] LC dynamics induced by the switching of an applied electric field can be spatially complex and are therefore best monitored by using microscopic methods. [4,5] We have recently developed an MPEFM-based time-resolved imaging method that allows for LC reorientation dynamics to be followed with ca. 250 nm spatial resolution and ca.…”

Section: Electric-field-induced Lc Dynamicsmentioning

confidence: 99%

“…Polymer-dispersed liquid crystals (PDLCs) represent an important subset of this class of materials, on which there exists a substantial body of contemporary literature. [1][2][3][4][5] Comprised of micrometer-sized LC droplets dispersed within the polymer matrix, PDLCs strongly scatter light and are opaque in their usual state. They can be switched to an optically transparent state by the application of an electric field.…”

Section: Introductionmentioning

confidence: 99%

Fabrication and Characterization of Polymer/Liquid Crystal Composite Diffractive Optics by Multiphoton Methods

Xie¹,

Ito²,

Higgins³

2007

Adv Funct Materials

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Direct‐write multiphoton photolithography is used to prepare electrically switchable diffraction gratings having spacings as small as 4 μm. Surface‐relief gratings are written into poly(methyl methacrylate) films using a sample‐scanning confocal microscope and are characterized by using contact‐mode atomic force microscopy. The resulting polymeric channels are filled with nematic liquid crystals (LCs) and sandwiched between indium tin oxide‐coated coverslips to obtain functional devices. These devices exhibit diffraction efficiencies approaching 30 %. Microscopic LC organization and field‐induced reorientation dynamics within these devices are characterized by static and dynamic polarization‐dependent multiphoton excited fluorescence microscopy. LCs are found to align predominantly along the channel axis, but exhibit some disorder near the channel walls, resulting from nanometer‐scale polymer surface roughness. LC reorientation in response to an electric field is rapid (<1 ms) and uniform, whereas field‐free LC relaxation is relatively slow (>20 ms). Both reorientation and relaxation are influenced by orientationally anchored LCs near the channel walls.

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“…Polymer dispersed liquid crystal (PDLC) films consist of randomly distributed micrometer-sized liquid crystal (LC) droplets embedded in an isotropic polymer matrix, and have attracted considerable interest for both technological and for more fundamental reasons [1,2,3,4].…”

Section: Introductionmentioning

confidence: 99%

Ordering of droplets and light scattering in polymer dispersed liquid crystal films

Kiselev

Yaroshchuk

Dolgov

2004

J. Phys.: Condens. Matter

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We study the effects of droplet ordering in initial optical transmittance through polymer dispersed liquid crystal (PDLC) films prepared in the presence of an electrical field. The experimental data are interpreted by using a theoretical approach to light scattering in PDLC films that explicitly relates optical transmittance and the order parameters characterizing both the orientational structures inside bipolar droplets and orientational distribution of the droplets. The theory relies on the Rayleigh-Gans approximation and uses the Percus-Yevick approximation to take into account the effects due to droplet positional correlations.

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Probing the Mesoscopic Chemical and Physical Properties of Polymer-Dispersed Liquid Crystals

Cited by 152 publications

References 84 publications

Phase Behavior of Poly(butyl acrylate) Networks in Nematic Liquid Crystal Solvents

Phase Behavior of Poly(butyl acrylate) Networks in Nematic Liquid Crystal Solvents

Fabrication and Characterization of Polymer/Liquid Crystal Composite Diffractive Optics by Multiphoton Methods

Ordering of droplets and light scattering in polymer dispersed liquid crystal films

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