Bandwidth-controllable reflective polarisers based on the temperature-dependent chiral conflict in binary chiral mixtures

Abstract

In this study, we demonstrate a new method for obtaining a binary chiral mixture (BCM) which exhibits an unprecedented temperature-dependent helical twisting power (HTP) by utilising the chiral conflict between two chiral dopants with opposite handedness and HTP temperature dependence. Different from the common chiral dopant reported before, the addition of such a BCM could increase the clearing temperature of the host liquid crystal (LC). Due to the sufficiently large HTP value of the BCM, the three primary colours (blue, green and red) can be easily reflected by the nematic liquid crystal (N-LC)/BCM mixture at different temperatures. Moreover, the large HTP temperature dependence could be maintained and even enhanced in the longer wavelength region by adjusting the content of the BCM. Finally, based on the large HTP temperature dependence and the positive affect on the host LC of the BCM, a thermally bandwidth-controllable reflective polariser that could work in the visible region (400–750 nm) was prepared from the N-LC/BCM/polymer network composite.

Keywords:

• liquid crystal
• chiral dopant
• chiral conflict
• helical twisting power
• selective reflection

Acknowledgements

This work was supported by the National Natural Science Fund for Distinguished Young Scholar (Grant No. 51025313), National Natural Science Foundation (Grant No. 50973010), Flat-Panel Display Special Project of China 863 Plan (Grant No. 2008AA03A318), Projects of Chinese National Science Tackling Key Problems (Grant No. 2007BAE31B02), and Science and Technology Project of Beijing, China (Grant No. D090803044209001).