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Full-Text Articles in Physics
Light-Scattering From Polymer-Dispersed Liquid-Crystal Films - Droplet Size Effects, G, Paul Montgomery Jr, John L. West, W Tamuralis
Light-Scattering From Polymer-Dispersed Liquid-Crystal Films - Droplet Size Effects, G, Paul Montgomery Jr, John L. West, W Tamuralis
John L West
The effects of droplet size on light scattering by polymer-dispersed liquid crystal (PDLC) films have been studied theoretically and experimentally. Rayleigh-Gans calculations predict that, provided the droplets scatter independently, backscattering will be maximum at wavelength lambda when the droplet radius is about lambda/7. noticeable for droplet volume fractions eta above about 0.2 and shift the radius for maximum backscattering to about lambda/5 as eta increases to 0.5. These calculations are consistent with hemispherical transmittance and reflectance measurements on PDLC films in which multiple scattering is known to be important. These measurements indicate that solar attenuation by PDLC films will probably …
Drag On Particles In A Nematic Suspension By A Moving Nematic-Isotropic Interface, John L. West, A Glushchenko, Gx Liao, Y Reznikov, D Andrienko, Mp Allen
Drag On Particles In A Nematic Suspension By A Moving Nematic-Isotropic Interface, John L. West, A Glushchenko, Gx Liao, Y Reznikov, D Andrienko, Mp Allen
John L West
We report a clear demonstration of drag on colloidal particles by a moving nematic-isotropic interface. The balance of forces explains our observation of periodic, striplike structures that are produced by the movement of these particles.
Field-Induced Polymer Wall Formation In A Bistable Smectic-A Liquid Crystal Display, Ebru A. Buyuktanir, Nadina Gheorghiu, John L. West, Maxim Mitrokhin, Borre Holter, Anatoliy Glushchenko
Field-Induced Polymer Wall Formation In A Bistable Smectic-A Liquid Crystal Display, Ebru A. Buyuktanir, Nadina Gheorghiu, John L. West, Maxim Mitrokhin, Borre Holter, Anatoliy Glushchenko
John L West
We developed a composite system to produce robust bistable smectic-A (SmA) liquid crystal based flexible displays by encapsulating the liquid crystal material in a polymer wall structure. While keeping all the intrinsic bistable properties of the SmA material, the field-induced polymer walls bridge the two display substrates and bring significant advantages over the polymer dispersed liquid crystal structure. Here we analyze the performance of an encapsulated pixel and demonstrate superior electro-optical characteristics, high contrast ratio, and excellent sunlight readability. (c) 2006 American Institute of Physics.
Photo-Orientation Of Liquid Crystals Due To Light-Induced Desorption And Adsorption Of Dye Molecules On An Aligning Surface, E. Ouskova, Yurii Reznikov, S. V. Shiyanovskii, L. Su, John L. West, O. V. Kuksenok, O. Francescangeli, F. Simoni
Photo-Orientation Of Liquid Crystals Due To Light-Induced Desorption And Adsorption Of Dye Molecules On An Aligning Surface, E. Ouskova, Yurii Reznikov, S. V. Shiyanovskii, L. Su, John L. West, O. V. Kuksenok, O. Francescangeli, F. Simoni
John L West
We show that adsorption of dye molecules control the light-induced alignment of dye-doped nematic liquid crystal (LC) on a nonphotosensitive polymer surface. The dependencies of light-induced twist structures on exposure, thermal baking, thickness, and aging before irradiation of the LC cells allowed us to propose the following mechanism for the alignment. Before irradiation, the “dark”-adsorbed layer on the tested surface is formed from dye molecules predominantly aligned along the initial direction of the director. Irradiation of the cell with linearly polarized light produces an additional layer with different orientational ordering of dye molecules. The final easy axis is determined by …
Organic Thin-Film Transistor-Driven Polymer-Dispersed Liquid Crystal Displays On Flexible Polymeric Substrates, C. D. Sheraw, L. Zhou, J. R. Huang, D. J. Gundlach, T. N. Jackson, M. G. Kane, I. G. Hill, M. S. Hammond, J. Campi, B. K. Greening, J. Franci, John L. West
Organic Thin-Film Transistor-Driven Polymer-Dispersed Liquid Crystal Displays On Flexible Polymeric Substrates, C. D. Sheraw, L. Zhou, J. R. Huang, D. J. Gundlach, T. N. Jackson, M. G. Kane, I. G. Hill, M. S. Hammond, J. Campi, B. K. Greening, J. Franci, John L. West
John L West
We have fabricated organic thin-film transistor (OTFT)-driven active matrix liquid crystal displays on flexible polymeric substrates. These small displays have 16×16 pixel polymer-dispersed liquid crystal arrays addressed by pentacene active layer OTFTs. The displays were fabricated using a low-temperature process (<110 °C) on flexible polyethylene naphthalate film and are operated as reflective active matrix displays.
A Method For The Formation Of Polymer Walls In Liquid Crystal Polymer Mixtures, Yoan Kim, Jim Francl, Bahman Taheri, John L. West
A Method For The Formation Of Polymer Walls In Liquid Crystal Polymer Mixtures, Yoan Kim, Jim Francl, Bahman Taheri, John L. West
John L West
We have investigated the formation of polymer walls for high polymer content Liquid crystal (LC) formulations, using a patterned electric field to induce phase separation. The effect of this field on the phase separation temperature of a LC/monomer mixture is studied as a function of the photopolymerizable monomer concentration. The phase separation temperature increases with the patterned field strength. The application of a patterned field results in segregation of the LC molecules in the high electric field regions, i.e., pixels, whereas the monomers segregate in the low-field regions, i.e., interpixels. Subsequent photopolymerization results in the formation of polymer walls around …
Cholesteric Polymer-Dispersed Light Shutters, John L. West, R. B. Akins, J. Francl, J. W. Doane
Cholesteric Polymer-Dispersed Light Shutters, John L. West, R. B. Akins, J. Francl, J. W. Doane
John L West
We report cholesteric/polymer dispersed (CPD) materials that switch from a reflecting, planar state to a relatively transparent, focal conic state. The reflective wavelength of the CPD materials can be continuously adjusted by varying the cholesteric pitch length. The electro‐optic properties of these materials are similar to the recently reported polymer stabilized cholesteric materials; however, the polymer concentration is sufficient to provide a self‐sustaining and self‐adhering film, offering the potential of large area devices fabricated on flexible substrates.
Characterization Of Polymer Dispersed Liquid-Crystal Shutters By Ultraviolet Visible And Infrared-Absorption Spectroscopy, John L. West, R. Ondris-Crawford
Characterization Of Polymer Dispersed Liquid-Crystal Shutters By Ultraviolet Visible And Infrared-Absorption Spectroscopy, John L. West, R. Ondris-Crawford
John L West
Incorporation of dichroic dyes substantially improves the contrast of polymer dispersed liquid‐crystal(PDLC) shutters. The efficiency of dichroic dyes in a PDLC shutter depends on the scattering efficiency of the film, the dichroic ratio of the dye, the order parameter of the dye in the liquid crystal, and the fraction of dye dissolved in the droplets. Ultraviolet/visible spectroscopy can be effectively used to determine the scattering efficiency of PDLCfilms, and the distribution of dichroic dye dissolved in the liquid‐crystaldroplets. To achieve high contrast the dichroic dye must be segregated in the droplet. We show that the segregation of dye in the …