Synthesis and Characterization of Redox-Responsive Chiral Liquid Crystal Monomers and Application to Bandwidth Broadening of Polymer Stabilized Cholesteric Liquid Crystals
Abstract
The development of chirophotonic crystals using cholesteric liquid crystal (CLC) molecules has generated significant interest. CLC materials selectively reflect circularly polarized light (CPL) depending on the handedness of helical pitch. Two new ionic monomers will be developed- ferrocene containing chiral monomers and ionic chiral complexes. The use of CLC materials for dynamic polarizers, switchable mirrors, and data storage devices requires study on larger and reconfigurable bandwidths. Various approaches have been reported for controlling the bandwidth of CLC. White and his group recently investigated the electro-optical (EO) response of polymer-stabilized cholesteric liquid crystals (PSCLCs) with negative dielectric anisotropy, such as notch tuning and bandwidth broadening responses, to achieve this goal. However, the dynamic response of PSCLC is relatively slow and requires a high driving voltage. To improve these issues, new monomers containing redox-responsive moieties have been introduced. Oxidized ferrocene moieties act as ionic molecules in the liquid crystal polymer networks. This study focuses on developing a set of novel redox-responsive and ionic chiral reactive mesogens to determine to improve the response of PSCLCs. This information will help to elucidate the EO performances of PSCLC, particularly with respect to the critical nature of ions. The chiral ionic complex molecule will also be developed to prepare CLCs with high reflectivity (greater thangreater than50percent) in a single cell. Previous studies have suggested that the EO response of PSCLC depends on the trapped ions in the polymer network affecting the distortion of the polymer network. When an electric field is applied, the ions trapped in the polymer network start to move and deform the polymer network, causing a pitch change across the cell thickness. An initially neutral ionic chiral molecule can be separated into two parts, the left-handed (LH) negatively charged part and right-handed (RH) positively charged part, when an electric field is applied, and migrate to the opposite electrode. The separated LH and RH ionic molecules migrate to opposite electrodes, creating a CLC sample with LH CLC on one side and RH CLC on the other side in a single cell, resulting very high reflectivity. This LC device could be a good candidate for low-power-consumption reflective displays, such as e-paper, which only require electric power when creating a display image.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 16, 2024
- Source ID
- FA23862314056
Entities
People
- Kwang-Un Jeong
Organizations
- Air Force Office of Scientific Research
- Jeonbuk National University
- United States Air Force