Efficient defect healing in cholesteric liquid crystals

Wei-Shiang Chiu¹, Jia-De Lin^1*

¹Department of Opto-Electronic Engineering, National Dong Hwa University, Hualien, Taiwan

* Presenter:Jia-De Lin, email:jdlin1218@gms.ndhu.edu.tw

Cholesteric liquid crystals (CLCs), with their self-assembled helical structures, act as one-dimensional chiral photonic crystals exhibiting photonic band gaps. However, structural defects can disrupt their periodicity and degrade optical performance. In this work, we propose a simple and effective thermal annealing strategy to eliminate defects in CLCs by selectively inducing localized phase transitions in disordered regions. We identify an optimal annealing temperature for each CLC composition, at which defect regions, owing to their lower thermal stability, undergo an isotropic transition, while well-aligned regions retain their liquid crystalline order. Upon cooling, the preserved ordered domains guide the reformation of helical alignment in previously disordered areas. This selective healing mechanism significantly improves structural uniformity and optical reflectivity. The approach is compatible with various CLC systems, including low-molecular-weight mixtures, polymer-stabilized and templated CLCs, and even precursor states of all-polymeric cholesterics. Its efficiency, scalability, and broad applicability make it a promising route for fabricating high-quality soft photonic crystals and advanced photonic devices.

Keywords: cholesteric liquid crystal, defect, chiral photonic crystal, thermal annealing