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.
Highlights
Cholesteric liquid crystals (CLC) are a class of organic small molecules that selforganize into a one-dimensional photonic material with a helicoidal superstructure
We have previously reported on the initiator-less polymerization of liquid crystal monomers (LCMs) to form
The conversion of the acrylate groups of light, radicals were generated in the LCM melts or LC mixtures and confirmed by electron liquid crystal monomer was monitored using in situ FTIR measurements, and liquid crystalline networks (LCNs) paramagnetic resonance (EPR) measurement
Summary
Cholesteric liquid crystals (CLC) are a class of organic small molecules that selforganize into a one-dimensional photonic material with a helicoidal superstructure. It is well known that CLCs with positive dielectric anisotropy (∆ε > 0) pass through the metastable focal-conic state upon relaxation from the field-induced homeotropic state to the planar cholesteric state [3,4,5]. This relaxation process is relatively slow and, in many cases, polymer stabilization is used to improve the relaxation kinetics [6,7,8].
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