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Radka BP, Pande GK, White TJ. The contribution of network elasticity to electro-optic response in polymer stabilized cholesteric liquid crystals. SOFT MATTER 2023. [PMID: 37161870 DOI: 10.1039/d3sm00225j] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Polymer stabilization of cholesteric liquid crystals can enable dynamic reconfiguration of the selective reflection of the CLC phase. Here, we explore how the contribution of the elasticity of the polymer stabilizing network affects the ion-mediated, electromechanical deformation and associated electro-optic response in PSCLCs. We utilize a free-radical chain transfer reaction between acrylate and thiol monomers that has been used to prepare elastomeric networks. This work maps the compositional contributions of total concentration and crosslink density to tuning and recovery.
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Affiliation(s)
- Brian P Radka
- Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309, USA.
| | - Gaurav K Pande
- Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309, USA.
| | - Timothy J White
- Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309, USA.
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Lee KM, Marsh ZM, Crenshaw EP, Tohgha UN, Ambulo CP, Wolf SM, Carothers KJ, Limburg HN, McConney ME, Godman NP. Recent Advances in Electro-Optic Response of Polymer-Stabilized Cholesteric Liquid Crystals. MATERIALS (BASEL, SWITZERLAND) 2023; 16:2248. [PMID: 36984126 PMCID: PMC10053326 DOI: 10.3390/ma16062248] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 03/01/2023] [Accepted: 03/06/2023] [Indexed: 06/18/2023]
Abstract
Cholesteric liquid crystals (CLC) are molecules that can self-assemble into helicoidal superstructures exhibiting circularly polarized reflection. The facile self-assembly and resulting optical properties makes CLCs a promising technology for an array of industrial applications, including reflective displays, tunable mirror-less lasers, optical storage, tunable color filters, and smart windows. The helicoidal structure of CLC can be stabilized via in situ photopolymerization of liquid crystal monomers in a CLC mixture, resulting in polymer-stabilized CLCs (PSCLCs). PSCLCs exhibit a dynamic optical response that can be induced by external stimuli, including electric fields, heat, and light. In this review, we discuss the electro-optic response and potential mechanism of PSCLCs reported over the past decade. Multiple electro-optic responses in PSCLCs with negative or positive dielectric anisotropy have been identified, including bandwidth broadening, red and blue tuning, and switching the reflection notch when an electric field is applied. The reconfigurable optical response of PSCLCs with positive dielectric anisotropy is also discussed. That is, red tuning (or broadening) by applying a DC field and switching by applying an AC field were both observed for the first time in a PSCLC sample. Finally, we discuss the potential mechanism for the dynamic response in PSCLCs.
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Affiliation(s)
- Kyung Min Lee
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433, USA
- Azimuth Corporation, Beavercreek, OH 45431, USA
| | - Zachary M. Marsh
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433, USA
- Azimuth Corporation, Beavercreek, OH 45431, USA
| | - Ecklin P. Crenshaw
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433, USA
- Azimuth Corporation, Beavercreek, OH 45431, USA
| | - Urice N. Tohgha
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433, USA
- Azimuth Corporation, Beavercreek, OH 45431, USA
| | - Cedric P. Ambulo
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433, USA
- Azimuth Corporation, Beavercreek, OH 45431, USA
| | - Steven M. Wolf
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433, USA
- Azimuth Corporation, Beavercreek, OH 45431, USA
| | - Kyle J. Carothers
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433, USA
- Azimuth Corporation, Beavercreek, OH 45431, USA
| | - Hannah N. Limburg
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433, USA
- Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Michael E. McConney
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433, USA
| | - Nicholas P. Godman
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, OH 45433, USA
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Sun LY, Wang XY, Chen JH, Li CY, Ma LL, Lu YQ, Li BX. Electrical modification of order parameters and director fluctuations in a dielectrically negative nematic doped with a positive additive. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Effect of Ion Concentration on the Electro-Optic Response in Polymer-Stabilized Cholesteric Liquid Crystals. CRYSTALS 2020. [DOI: 10.3390/cryst11010007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have previously reported that the application of a DC field can adjust the position and/or bandwidth of the selective reflection notch in polymer-stabilized cholesteric liquid crystals (PSCLCs). The proposed mechanism of these electro-optic (EO) response is ion-facilitated electromechanical deformation of the polymer stabilizing network. Accordingly, the concentration of ions trapped within the polymer network should considerably influence the EO response of PSCLC. Our prior studies have indicated that photoinitiators can increase ion density in PSCLC by an order of magnitude. Here, we isolate the contribution of ionic impurities associated with liquid crystal monomers (LCMs) by utilizing initiator-less polymerization. PSCLCs prepared with LCM with low ion concentration show bandwidth broadening of the reflection band whereas PSCLCs prepared with LCM with high ion concentration exhibit a red shifting tuning of the reflection band. The extent of the tuning or bandwidth broadening of the CLC reflection band depends on the concentration of LCMs and the chirality of the LCM.
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