Controlling pitch length of chiral monomer-doped nematic/cholesteric liquid crystals using photopolymerization

• Published in: Journal of physics. D, Applied physics Vol. 43; no. 50; p. 505102
• Main Authors: Liu, Cheng-Kai, Fuh, Andy Ying-Guey, Chen, Yuan-Di, Cheng, Ko-Ting
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 22.12.2010; Institute of Physics
• Subjects: Applied sciences; Bulk polymerization; Cholesteric liquid crystals; Competition; Diffusion; Dopants; Exact sciences and technology; Nematic; Organic polymers; Photopolymerization; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Scanning electron microscopy; Doping; Operating mode; Irreversible process; Polymer; Experimental device; Liquid crystals; Nematic crystals; Absorption spectrum; Structure processing relationship; Ultraviolet radiation; Photopolymerization; Cholesteric crystals
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/43/50/505102

This work presents a simple approach to control the pitch length of chiral monomer-doped nematic/cholesteric liquid crystals (CM-NLCs/CM-CLCs) using photopolymerization. Illuminating CM-NLCs/CM-CLCs with unpolarized UV light causes the diffusion and polymerization of CM, and then increases/decreases the pitch length by reducing the concentration of the CM in the bulk. It should be noted that the pitch length change is irreversible in either red- or blue-shift. The key to control the pitch length of CM-NLCs/CM-CLCs is the competition between the right- and left-hand chiral dopants in the sample. CM-NLCs and CM-CLCs are used to study the red- and blue-shifts, respectively. The properties of cobweb-like polymer layers are also discussed.