Maximizing Orientational Order in Polymer-Stabilized Liquid Crystals Using High Magnetic Fields

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• 作者：Alexandra Alvarez Fernandez ; Masoumeh Keshavarz ; Peter C. M. Christianen ; Paul H. J. Kouwer
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：February 24, 2015
• 年：2015
• 卷：48
• 期：4
• 页码：1002-1008
• 全文大小：369K
• ISSN：1520-5835

文摘

Polymer-stabilized liquid crystals (PSLCs) are materials composed of a polymer mesh in a continuous phase of liquid crystal. The polymer mesh provides an anchor point for alignment of the liquid crystalline bulk. The macroscopic extent of order in such systems depends on the order parameter of the liquid crystal (given by the temperature) and the domain order parameter, induced by external stimuli, such as (rubbed) substrates or magnetic or electric fields. We studied thick PSLCs where substrate interactions cannot be employed and used magnetic fields instead. We show how the polymerization conditions, i.e., the temperature and the magnetic field, influence the overall order parameter in 4-octyl-4鈥?cyanobiphenyl (8CB)-based PSLCs. Optimal macroscopic alignment was obtained in samples polymerized at room temperature and at magnetic fields in excess of 5 T. The effect of mesh network can be quantified by introducing a phenomenological constant, which is correlated to the order parameter at the polymerization conditions, into a straightforward model that describes the overall order parameter in terms of a thermally dependent local order parameter and a magnetic field dependent domain order parameter.