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Electro-Optical Properties of a Polymer Dispersed and Stabilized Cholesteric Liquid Crystals System Constructed by a Stepwise UV-Initiated Radical/Cationic Polymerization

1
Department of Materials Physics and Chemistry, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
2
State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China
3
Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Crystals 2019, 9(6), 282; https://doi.org/10.3390/cryst9060282
Received: 20 March 2019 / Revised: 8 May 2019 / Accepted: 22 May 2019 / Published: 29 May 2019
(This article belongs to the Special Issue Advances in Cholesteric Liquid Crystals)
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Abstract

Polymer-dispersed liquid crystal (PDLC) and polymer-stabilized liquid crystal (PSLC) are two typical liquid crystal (LC)/polymer composites. PDLCs are usually prepared by dispersing LC droplets in a polymer matrix, while PSLC is a system in which the alignment of LC molecules is stabilized by interactions between the polymer network and the LC molecules. In this study, a new material system is promoted to construct a coexistence system of PDLC and PSLC, namely PD&SChLC. In this new material system, a liquid-crystalline vinyl-ether monomer (LVM) was introduced to a mixture containing cholesteric liquid crystal (ChLC) and isotropic acrylate monomer (IAM). Based on the different reaction rates between LVM and IAM, the PD&SChLC architecture was built using a stepwise UV-initiated polymerization. During the preparation of the PDS&ChLC films, first, the mixture was irradiated with UV light for a short period of time to induce the free radical polymerization of IAMs, forming a phase-separated microstructure, PDLC. Subsequently, an electric filed was applied to the sample for long enough to induce the cationic polymerization of LVMs, forming the homeotropically-aligned polymer fibers within the ChLC domains, which are similar to those in a PSLC. Based on this stepwise UV-initiated radical/cationic polymerization, a PD&SChLC film with the advantages of a relatively low driving voltage, a fast response time, and a large-area processability is successful prepared. The film can be widely used in flexible displays, smart windows, and other optical devices. View Full-Text
Keywords: cholesteric liquid crystals; polymer; radical polymerization; cationic polymerization; electro-optical property; microstructure cholesteric liquid crystals; polymer; radical polymerization; cationic polymerization; electro-optical property; microstructure
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Li, C.-Y.; Wang, X.; Liang, X.; Sun, J.; Li, C.-X.; Zhang, S.-F.; Zhang, L.-Y.; Zhang, H.-Q.; Yang, H. Electro-Optical Properties of a Polymer Dispersed and Stabilized Cholesteric Liquid Crystals System Constructed by a Stepwise UV-Initiated Radical/Cationic Polymerization. Crystals 2019, 9, 282.

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