Cholesteric liquid crystal paints: in situ photopolymerization of helicoidally stacked multilayer nanostructures for flexible broadband mirrors

Dae-Yoon Kim,Timothy J. White,Kyung Min Lee,Kwang-Un Jeong

doi:10.1038/s41427-018-0096-4

Abstract

Utilizing sequential layer-by-layer (LBL) coating and subsequent photopolymerization, we developed circular-polarizing and free-standing mirrors with a broad reflection bandwidth. Photopolymerizable cholesteric liquid crystal (CLC) paints were first prepared by considering the intrinsic chirality and the coating viscoelasticity. The polymer-stabilized nanostructures had finely tuned helical pitches that selectively reflected light over the entire visible wavelength range. The CLC films exhibited excellent thermomechanical properties and chemical stabilities, which enabled the preparation of patterned optical objects at macroscopic dimensions. The LBL coating and photopolymerization of the CLC paints demonstrated here can provide a simple solution for manufacturing flexible photonic devices with large areas at low cost.

Highlights

The structural color and light control of photonic crystals have been the subject of intensive research[1]
Based on the helical twisting power (HTP) of the chiral RM (cRM), the cholesteric liquid crystal (CLC) paints are formulated with cRM:monoacrylate monomer (mRM): diacrylate monomer (dRM) weight percent ratios of 12:25:63, 10:25:65, and 8:25:67
The cholesteric mesophase of the CLC paints is only composed of the cRM and dRM, the mRM is added to prevent the crystallization of the mixture (Fig. 1b)

Summary

Introduction

The structural color and light control of photonic crystals have been the subject of intensive research[1]. When the periodic modulation due to the alternating high and low refractive indices is proportional to the visible wavelength region, the partial photonic bandgap is opened[3]. This light is completely reflected in the photonic crystal, and a selective wavelength with an iridescent color is observed[4]. Self-organized periodic structures found in nature inspire the design and synthesis of new photonic elements[7]

Methods

Results

Discussion

Conclusion