Effect of a Dual Functional Polymer on the Electro-Optical Properties of Blue Phase Liquid Crystals

Abstract

The effects of the fluorinated monomer with an ethynyl group on the electro-optical properties of polymer-stabilized blue phase liquid crystals (PSBPLCs) were investigated in different polymer systems. In rigid polymer systems, the Kerr constant can be increased by about 27.6%, while keeping a microsecond response time. In soft polymer systems, hysteresis decreased by about 45.5% and residual birefringence can be reduced from 1.85% to 0.6%. The above phenomena exhibited dual functions of affecting the anchoring energy and the viscosity of the system simultaneously. The results provide a potential value for the ethynyl-containing monomers in PSBPLC systems.

Polymer Stabilization of Uniform Lying Helix Texture in a Bimesogen-Doped Cholesteric Liquid Crystal for Frequency-Modulated Electro-Optic Responses

“…However, for the counterpart with the TMPTA content fully replaced by RM257, the polymer structure made from the bifunctional reactive monomer alone (at 5.0-wt%) in the RM50-CLC became insufficient to sustain the ULH helix, causing it to become unstable after the CLC helix was unwound. This underlines the importance of TMPTA, which has been found to play the role of promoting the crosslinking density and introducing rigidity to the resulting polymer network with RM257 [31,32].…”

“…As they were unraveled by the bright appearances in the optical images at α = 45° (e.g., Figure 5a at 25 °C), the PN-ULH textures in this heating process were preserved until T > Tiso = 60 °C, where the CLCs were in the isotropic phase with dark appearances in optical became insufficient to sustain the ULH helix, causing it to become unstable after the CLC helix was unwound. This underlines the importance of TMPTA, which has been found to play the role of promoting the crosslinking density and introducing rigidity to the resulting polymer network with RM257 [31,32]. Furthermore, the thermal stability of PN-ULH textures and their recoverability after thermally induced phase transition were assessed in accordance with simultaneous measurements of optical images and real-part dielectric permittivity (ε′) at varying temperatures as shown in Figure 5.…”

“…Unlike previously developed polymer networks employing a photocurable monomer with particular ultraviolet (UV) exposure conditions or with high concentrations [2,[21][22][23][24][25], the proposed one in this study was constructed by a monomer mixture containing a bifunctional monomer RM257 and a trifunctional monomer TMPTA, permitting the ULH texture to be highly stable and reversibly recoverable at a low concentration of 5-wt% in a total. So far, the polymer system involving the copolymerization of RM257 and TMPTA has widely been applied to the stabilization of blue phases in wide temperature ranges [31,32], but it has not been adopted for stabilizing the ULH texture until now. To demonstrate the unique combination of RM257 and TMPTA, another PN-ULH texture with RM257 alone was fabricated as a comparative counterpart.…”