Realisation of cholesteric liquid-crystalline materials reflecting both right- and left-circularly polarised light using the wash-out/refill technique

Abstract

In this study, a single-layer polymer-stabilised liquid crystal (PSLC) film reflecting both right- and left-circularly polarised light has been developed by a wash-out/refill method. A polymer network/liquid crystals (LCs) composite, in which the polymer network had a certain helical structure, was prepared by photo polymerisation of the photo-polymerisable LC monomers (LCMs) in a LCM/LC/photoinitiator mixture. Then, the LC molecules were extracted from the composite film and cholesteric LCs (Ch-LCs) with the opposite helical structure were refilled into the film. The film was constructed by the polymer network with a certain helical structure and Ch-LCs with the opposite helical structure could reflect both right- and left-circularly polarised light simultaneously. The reflection intensity of the film is close to 100% when the pitch lengths of the two opposite helical structures are the same, which goes beyond the 50% reflectance limit of Ch-LCs. It was demonstrated that the memory effect of the polymer network is an important mechanism for the resulting film properties.

Keywords:

• cholesteric liquid crystal
• circularly polarised light
• wash-out/refill
• polymer network
• memory effect

Acknowledgement

This research was supported by the National Natural Science Foundation (grant nos. 50903004 and 50673007).