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Shintson Wu - One of the best experts on this subject based on the ideXlab platform.

  • low voltage Polymer Network liquid crystal for infrared spatial light modulators
    Optics Express, 2015
    Co-Authors: Fenglin Peng, Daming Xu, Haiwei Chen, Shintson Wu
    Abstract:

    We report a low-voltage and fast-response Polymer Network liquid crystal (PNLC) infrared phase modulator. To optimize device performance, we propose a physical model to understand the curing temperature effect on average domain size. Good agreement between model and experiment is obtained. By optimizing the UV curing temperature and employing a large dielectric anisotropy LC host, we have lowered the 2π phase change voltage to 22.8V at 1.55μm wavelength while keeping response time at about 1 ms. Widespread application of such a PNLC integrated into a high resolution liquid-crystal-on-silicon (LCoS) for infrared spatial light modulator is foreseeable.

  • a low voltage submillisecond response Polymer Network liquid crystal spatial light modulator
    Applied Physics Letters, 2014
    Co-Authors: Shintson Wu, Yasuhiro Haseba
    Abstract:

    We report a low voltage and highly transparent Polymer Network liquid crystal (PNLC) with submillisecond response time. By employing a large dielectric anisotropy LC host JC-BP07N, we have lowered the V2π voltage to 23 V at λ = 514 nm. This will enable PNLC to be integrated with a high resolution liquid-crystal-on-silicon spatial light modulator, in which the maximum voltage is 24 V. A simple model correlating PNLC performance with its host LC is proposed and validated experimentally. By optimizing the domain size, we can achieve V2π < 15 V with some compromises in scattering and response time.

  • A low voltage submillisecond-response Polymer Network liquid crystal spatial light modulator
    Applied Physics Letters, 2014
    Co-Authors: Shintson Wu, Yasuhiro Haseba
    Abstract:

    We report a low voltage and highly transparent Polymer Network liquid crystal (PNLC) with submillisecond response time. By employing a large dielectric anisotropy LC host JC-BP07N, we have lowered the V2π voltage to 23 V at λ = 514 nm. This will enable PNLC to be integrated with a high resolution liquid-crystal-on-silicon spatial light modulator, in which the maximum voltage is 24 V. A simple model correlating PNLC performance with its host LC is proposed and validated experimentally. By optimizing the domain size, we can achieve V2π 

  • reconfigurable fabrication of scattering free Polymer Network liquid crystal prism grating lens
    Applied Physics Letters, 2013
    Co-Authors: Jie Sun, Hongwen Ren, Su Xu, Shintson Wu
    Abstract:

    We report a simple reconfigurable printing method for fabricating submillisecond-response and scattering-free Polymer Network liquid crystal photonic devices, such as prism, grating, and lens. To suppress light scattering in the visible region, we reduce the domain sizes by controlling Polymer concentration, selecting a high viscosity liquid crystal (LC) host, and performing UV curing at a low temperature. To demonstrate the configurability, we printed a LC micro-prism array with ∼300-μm feature size and a circular lens with 1.3-mm radius without any pre-patterned templates. This reconfigurable printing technique enables fast design iterations and should have widespread applications for fabricating display and photonic devices.

  • submillisecond response variable optical attenuator based on sheared Polymer Network liquid crystal
    Optics Express, 2004
    Co-Authors: Yunghsun Wu, Janet R Wu, Yanqing Lu, Shintson Wu
    Abstract:

    We demonstrate a variable optical attenuator (VOA) at λ=1.55 µm using a sheared Polymer Network liquid crystal (SPNLC). The SPNLC exhibits a fast response time and weak wavelength dependency. Comparing with other Polymer-stabilized liquid crystals, the SPNLC has lower driving voltage and negligible light scattering loss when the wavelength exceeds 700 nm. A reflection type VOA with ~0.24 ms response time and -32 dB dynamic range is demonstrated at room temperature and 35 Vrms voltage.

Christopher N. Bowman - One of the best experts on this subject based on the ideXlab platform.

  • a simple relationship relating linear viscoelastic properties and chemical structure in a model diels alder Polymer Network
    Macromolecules, 2012
    Co-Authors: Richard J Sheridan, Christopher N. Bowman
    Abstract:

    Although the gel point conversion of a thermoreversible Polymer Network is certainly a key parameter in determining the material properties, it is not a conventional liquid–solid transition as in c...

  • enhanced two stage reactive Polymer Network forming systems
    Polymer, 2012
    Co-Authors: Devatha P. Nair, Matthew K Mcbride, John C Gaipa, Neil B Cramer, Robin Shandas, Christopher N. Bowman
    Abstract:

    Abstract In this study, we develop thiol/acrylate two-stage reactive Network forming Polymer systems that exhibit two distinct and orthogonal stages of curing. Using a thiol-acrylate system with excess acrylate functional groups, a first stage Polymer Network is formed via a 1 to 1 stoichiometric thiol-acrylate Michael addition reaction (stage 1). At a later point in time, the excess acrylate functional groups are homoPolymerized via a photoinitiated free radical Polymerization to form a second stage Polymer Network (stage 2). By varying the monomers within the system as well as the stoichiometery of the thiol to acrylate functional groups, we demonstrate the ability of the two-stage Polymer Network forming systems to encompass a wide range of properties at the end of both the stage 1 and stage 2 Polymerizations. Using urethane di- and hexa-acrylates within the formulations led to two-stage reactive Polymeric systems with stage 1 T g s that ranged from −12 to 30° C. The systems were then photocured, upon which the T g of the systems increases by up to 90°C while also achieving a nearly 20 fold modulus increase.

  • two stage reactive Polymer Network forming systems
    Advanced Functional Materials, 2012
    Co-Authors: Devatha P. Nair, Matthew K Mcbride, John C Gaipa, Neil B Cramer, Robin Shandas, Emily M Matherly, Robert R Mcleod, Christopher N. Bowman
    Abstract:

    There are distinct advantages to designing Polymer systems that afford two distinct sets of material properties– an intermediate Polymer that would enable optimum handling and processing of the material, while maintaining the ability to tune in different, fi nal Polymer properties that enable the optimal functioning of the material. In this study, by designing a series of non-stoichiometric thiol-acrylate systems, a Polymer Network is initially formed via a base catalyzed Michael addition reaction that proceeds stoichiometrically via the thiol-acrylate “click” reaction. This self-limiting reaction results in a Polymer with excess acrylic functional groups within the Network. At a later point in time, the photoinitiated, free radical Polymerization of the excess acrylic functional groups results in a highly crosslinked, robust material system. These two stage reactive thiol-acrylate Networks that have intermediate stage rubbery moduli and glass transition temperatures that range from 0.5 MPa and − 10 ° C to 22 MPa and 22 ° C, respectively, are formulated and characterized. The same Polymer Networks can then attain glass transition temperatures that range from 5 ° C to 195 ° C and rubbery moduli of up to 200 MPa after the subsequent photocuring stage. The two stage reactive Networks formed by varying the stoichiometric ratios of the thiol and acrylate monomers were shown to perform as substrates for three specifi c applications: shape memory Polymers, impression materials, and as optical materials for writing refractive index patterns.

Ingo Dierking - One of the best experts on this subject based on the ideXlab platform.

  • Growth of a SmA* phase in the microconfinement of a Polymer Network
    Liquid Crystals, 2008
    Co-Authors: H. K. Chan, Ingo Dierking
    Abstract:

    The growth of a chiral smectic A (SmA*) phase after a temperature quench was investigated experimentally in the confinement of a stabilising Polymer Network. In contrast to the random orientation of bâtonnet domains observed for non‐stabilised smectic growth, all the growing Polymer‐stabilised SmA* bâtonnets are aligned in the same direction, as a result of the interactions between the Polymer Network and the liquid crystal (LC). Interestingly, for each growing bâtonnet with long axis R, the early‐time growth law changes from R ∼ t 1/2 to R ∼ t for increasing quench depth, as is also observed for non‐stabilised bâtonnet growth. This indicates that the previously reported crossover of the growth exponent from n = ½ to n = 1 for increasing quench depth may be universal, independent of sample dimension and confinement conditions. The growth dynamics of the SmA* phase is independent of the presence of the Polymer Network, even though interactions between the LC and the Polymer Network lead to clear structural...

  • Polymer Network stabilized liquid crystals
    Advanced Materials, 2000
    Co-Authors: Ingo Dierking
    Abstract:

    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.

  • Polymer Network–Stabilized Liquid Crystals
    Advanced Materials, 2000
    Co-Authors: Ingo Dierking
    Abstract:

    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.

Hongwen Ren - One of the best experts on this subject based on the ideXlab platform.

  • reconfigurable fabrication of scattering free Polymer Network liquid crystal prism grating lens
    Applied Physics Letters, 2013
    Co-Authors: Jie Sun, Hongwen Ren, Su Xu, Shintson Wu
    Abstract:

    We report a simple reconfigurable printing method for fabricating submillisecond-response and scattering-free Polymer Network liquid crystal photonic devices, such as prism, grating, and lens. To suppress light scattering in the visible region, we reduce the domain sizes by controlling Polymer concentration, selecting a high viscosity liquid crystal (LC) host, and performing UV curing at a low temperature. To demonstrate the configurability, we printed a LC micro-prism array with ∼300-μm feature size and a circular lens with 1.3-mm radius without any pre-patterned templates. This reconfigurable printing technique enables fast design iterations and should have widespread applications for fabricating display and photonic devices.

  • fast response and scattering free Polymer Network liquid crystals for infrared light modulators
    Applied Physics Letters, 2004
    Co-Authors: Yunhsing Fan, Yihsin Lin, Hongwen Ren, Sebastian Gauza
    Abstract:

    A fast-response and scattering-free homogeneously aligned Polymer Network liquid crystal (PNLC) light modulator is demonstrated at λ=1.55 μm wavelength. Light scattering in the near-infrared region is suppressed by optimizing the Polymer concentration such that the Network domain sizes are smaller than the wavelength. The strong Polymer Network anchoring assists LC to relax back quickly as the electric field is removed. As a result, the PNLC response time is ∼250× faster than that of the E44 LC mixture except that the threshold voltage is increased by ∼25×.

  • tunable electronic lens using a gradient Polymer Network liquid crystal
    Applied Physics Letters, 2003
    Co-Authors: Hongwen Ren
    Abstract:

    Tunable electronic lenses using gradient Polymer Network liquid crystal (PNLC) cells were demonstrated. By changing the photomask pattern, both positive and negative lenses were fabricated. The advantages of such a PNLC lens are low operation voltage, large aperture size, and simple electrode design. To overcome the polarization dependence, stacking two orthogonal homogeneous PNLC cells is considered.

Debabrata Chakrabarty - One of the best experts on this subject based on the ideXlab platform.

  • characterization of nanocellulose reinforced semi interpenetrating Polymer Network of poly vinyl alcohol polyacrylamide composite films
    Carbohydrate Polymers, 2015
    Co-Authors: Arup Ratan Mandal, Debabrata Chakrabarty
    Abstract:

    Semi-interpenetrating Polymer Network (semi-IPN) of poly(vinyl alcohol)/polyacrylamide was reinforced with various doses of nanocellulose. The different composite films thus prepared were characterized with respect to their mechanical, thermal, morphological and barrier properties. The composite film containing 5 wt.% of nanocellulose showed the highest tensile strength. The semi-interpenetrating Polymer Network of poly(vinyl alcohol)/polyacrylamide; and its various composites with nanocellulose were almost identical in their thermal stability. Each of the composites however exhibited much superior stability with respect to the linear poly(vinyl alcohol) and crosslinked polyacrylamide. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies exhibited phase separated morphology where agglomerates of nanocellulose were found to be dispersed in the matrix of the semi-IPN. The moisture vapor transmission rate (MVTR) was the lowest for the film containing 5 wt.% of nanocellulose.

  • characterization of nanocellulose reinforced semi interpenetrating Polymer Network of poly vinyl alcohol polyacrylamide composite films
    Carbohydrate Polymers, 2015
    Co-Authors: Arup Ratan Mandal, Debabrata Chakrabarty
    Abstract:

    Semi-interpenetrating Polymer Network (semi-IPN) of poly(vinyl alcohol)/polyacrylamide was reinforced with various doses of nanocellulose. The different composite films thus prepared were characterized with respect to their mechanical, thermal, morphological and barrier properties. The composite film containing 5 wt.% of nanocellulose showed the highest tensile strength. The semi-interpenetrating Polymer Network of poly(vinyl alcohol)/polyacrylamide; and its various composites with nanocellulose were almost identical in their thermal stability. Each of the composites however exhibited much superior stability with respect to the linear poly(vinyl alcohol) and crosslinked polyacrylamide. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies exhibited phase separated morphology where agglomerates of nanocellulose were found to be dispersed in the matrix of the semi-IPN. The moisture vapor transmission rate (MVTR) was the lowest for the film containing 5 wt.% of nanocellulose.