Switchable Bragg Gratings Formed in Situ Within a Polymer-Dispersed Liquid Crystal Composite Medium

1996 ◽  
Vol 425 ◽  
Author(s):  
R. L. Sutherland ◽  
L. V. Natarajan ◽  
T. J. Bunning ◽  
V. P. Tondiglia ◽  
W. W. Adams
Keyword(s):  
Liquid Crystal ◽  
Wave Theory ◽  
Acrylate Monomer ◽  
Polymer Dispersed Liquid Crystal ◽  
Unique System ◽  
Polymer Dispersed ◽  
Potential Applications ◽  
Microscopic Morphology ◽  
Photo Curing

AbstractHolographic photo-curing of a penta-acrylate monomer-liquid crystal mixture forms a unique system of liquid crystal microdomains confined to Bragg planes. We examine the physics of this structure as it relates to the formation of electrically switchable holograms, for which many potential applications exist. The results of scanning electron microscopy and laser characterization studies lead to the development of concepts and models for explaining the microscopic morphology and electro-optical properties of these holograms. We find that a model incorporating a shaped-droplet analysis of the electro-mechanical properties of LC domains combined with standard coupled-wave theory of holography offers good numerical agreement with diffraction efficiency data for ppolarized probe light.

Holographic Polymer Dispersed Liquid Crystals: Effect of Partial Matrix Fluorination on Electro-Optical and Morphological Properties

2001 ◽  
Vol 709 ◽  
Author(s):  
Michael D. Schulte ◽  
Stephen J. Clarson ◽  
Lalgudi V. Natarajan ◽  
C. Allan Guymon ◽  
Timothy J. Bunning
Keyword(s):  
Liquid Crystal ◽  
Low Voltage ◽  
Morphological Properties ◽  
Acrylate Monomer ◽  
Polymer Dispersed Liquid Crystal ◽  
Morphological Studies ◽  
Polymer Dispersed Liquid Crystals ◽  
The Matrix ◽  
Polymer Dispersed ◽  
Morphological Differences

ABSTRACTHolographic polymer dispersed liquid crystal (H-PDLC) films with partially fluorinated matrices were investigated. Electro-optical and morphological studies revealed that fluorinated composites were substantially different from non-fluorinated analogues. The addition of a fluorinated monofunctional acrylate monomer to a pentaacrylate-derived polymer matrix resulted in improved diffraction efficiency. These findings suggest that the partial fluorination of the host polymer decreases the compatibility between the matrix and liquid crystal phase. Morphological differences between fluorinated films and non-fluorinated control specimens were verified using low-voltage, high-resolution scanning electron microscopy (LVHRSEM).

Bistable polymer-dispersed cholesteric liquid crystal thin film enabled by a stepwise polymerization

RSC Advances ◽  
2015 ◽  
Vol 5 (73) ◽  
pp. 58959-58965 ◽  
Author(s):  
Huihui Wang ◽  
Ling Wang ◽  
Mei Chen ◽  
Tongda Li ◽  
Hui Cao ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Liquid Crystal ◽  
Cholesteric Liquid Crystal ◽  
Polymer Network ◽  
Dielectric Anisotropy ◽  
Polymer Dispersed Liquid Crystal ◽  
Polymer Dispersed ◽  
Photo Curing

By using a proper polymer network and an ion-doped cholesteric liquid crystal with negative dielectric anisotropy, bistable polymer-dispersed liquid crystal thin films were prepared by first photo-curing, and then thermally curing.

In Situ Diffusion and Miscibility Studies of Thermoplastic PDLC Systems by FT-IR Microspectroscopy

1997 ◽  
Vol 51 (3) ◽  
pp. 297-303 ◽  
Author(s):  
Sudarsana R. Challa ◽  
Shi-Qing Wang ◽  
Jack L. Koenig
Keyword(s):  
Liquid Crystal ◽  
Phase Diagrams ◽  
Butyl Methacrylate ◽  
Contact Method ◽  
Polymer Dispersed Liquid Crystal ◽  
Polymer Dispersed ◽  
Ir Microspectroscopy ◽  
In Situ Diffusion ◽  
Miscibility Studies

Infrared microspectroscopy was used to study the interaction of liquid crystal (E7) with poly( n-butyl methacrylate) (PBMA). A novel experimental technique is introduced to conduct in situ diffusion and miscibility studies of polymer-dispersed liquid crystal (PDLC) systems. The amount of liquid crystal dissolved in the polymer matrix is determined by using the IR microspectroscope, which is a powerful tool for characterizing domains on the order of tens of micrometers. Quantitative phase diagrams are constructed for the PBMA and E7 mixture. It is observed that the diffusion of E7 into PBMA follows Fick's second law of diffusion with a diffusion coefficient of (1.3 ± 0.2) × 10−7 cm2/s at 61 °C. The intensities of the peaks in the IR spectrum were used as a measure of the concentration of the components. The combination of IR microspectroscopy with the contact method is proven to be a powerful technique for the quantitative elucidation of phase diagrams.

scholarly journals Polymer Dispersed Cholesteric Liquid Crystals With a Toroidal Director Configuration under an Electric Field

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 732
Author(s):  
Anna P. Gardymova ◽  
Mikhail N. Krakhalev ◽  
Victor Ya. Zyryanov ◽  
Alexandra A. Gruzdenko ◽  
Andrey A. Alekseev ◽  
...  
Keyword(s):  
Optical Properties ◽  
Liquid Crystal ◽  
Electric Field ◽  
Point Defects ◽  
Structural Response ◽  
Optical Filters ◽  
Response Curves ◽  
Polymer Dispersed Liquid Crystal ◽  
Dichroic Dye ◽  
Polymer Dispersed

The electro-optical properties of polymer dispersed liquid crystal (PDLC) films are highly dependent on the features of the contained liquid crystal (LC) droplets. Cholesteric LC droplets with homeotropic boundaries can form several topologically different orientational structures, including ones with single and more point defects, layer-like, and axisymmetric twisted toroidal structures. These structures are very sensitive to an applied electric field. In this work, we have demonstrated experimentally and by computer simulations that twisted toroidal droplets reveal strong structural response to the electric field. In turn, this leads to vivid changes in the optical texture in crossed polarizers. The response of droplets of different sizes were found to be equivalent in terms of dimensionless parameters. In addition, the explanation of this phenomenon showed a comparison of theoretical and experimental structural response curves aids to determine the shape of the droplet. Finally, we demonstrated that the addition of a dichroic dye allows such films to be used as optical filters with adjustable color even without polarizers.

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