Controlling Dual Reflection Bands of Cholesteric Liquid Crystal Polymer Network Films via Photoisomerization and Polymerization-Induced Molecular Migration

Cholesteric liquid crystal polymer network (CLCN) films featuring dual reflection bands have emerged as promising materials for decorative and anticounterfeiting applications, owing to their unique composite structural colors. Currently, these films are commonly fabricated via layer-by-layer stacking or two-step coating techniques. For large-scale manufacturing on industrial coating lines, however, a straightforward single-step coating process is far more desirable for its simplicity and cost effectiveness. In this work, we prepared photochromic cholesteric liquid crystal mixtures by combining a dimethacrylate-based liquid crystal monomer with a photoisomerizable chiral dopant. Based on the oxygen inhibition effect, we successfully fabricated CLCN films with intrinsic dual reflection bands via a single bar-coating process followed by two sequential photopolymerization steps. Both the photoisomerization of the chiral dopant and polymerization-induced molecular migration (PIMM) play critical roles in regulating the central wavelengths of the two reflection bands. Specifically, photoisomerization of the chiral dopant drives the longer-wavelength reflection band to red-shift, while PIMM causes this band to blue-shift, enabling precise modulation of the dual-band response. As a demonstration, we fabricated a patterned CLCN film with vivid composite structural colors, which shows excellent suitability for decorative applications. Furthermore, we verified that a composite film integrating a patterned CLCN, a quarter waveplate, and a linear polarizer can effectively function as an antipeeping optical film for information protection.