Freestanding Helical Nanostructured Chiro‐Photonic Crystal Film and Anticounterfeiting Label Enabled by a Cholesterol‐Grafted Light‐Driven Molecular Motor

Abstract

Design and fabrication of freestanding chiro‐photonic crystal film with the ability to change color over the whole visible light spectrum is appealing for anticounterfeiting technology and smart labels. Utilizing a newly synthesized light‐responsive molecular motor functionalized with cholesterol (chol‐MM) on the rotor, novel light‐controlled photonic crystal is prepared by doping the novel chol‐MM into liquid crystals (LCs). Thanks to the liquid crystalline cholesterol substituent, the chol‐MM can be triggered by visible light (420 nm). At the same time, the miscibility of chol‐MM in LC matrix is significantly enhanced. Integrating the chol‐MM with thermochromic hydrogen‐bonded LC matrix, thermal and light dual‐responsive cholesteric LC (CLC) material is prepared, in which the nanoscale helical pitch is tunable by photo‐induced molecular motions of chol‐MM. More importantly, utilizing UV‐initiated polymerization of the visible light‐modulated CLC material, structural colored photonic crystal films with arbitrary colorful patterns are fabricated. Such freestanding helical nanostructured labels have potential in the application of encrypted communication and anticounterfeiting.

Amplifying Molecular Scale Rotary Motion: The Marriage of Overcrowded Alkene Molecular Motor with Liquid Crystals

“…Very recently, our group extent this work by doping a cholesterol-grafted OAMM into a thermochromic LC matrix. [61] The reflective band of prepared CLC changed over the whole visible range by visible light exposure and heating, enabling the preparation of freestanding optical labels.…”

Light Intensity-Selective Photopolymerization and Photoisomerization for Creating Colorful Polymer-Stabilized Cholesteric Liquid Crystal Patterns

“…The PSCLC films can be used as sensors for temperature, humidity, and chemicals . Recent results indicated that they could be used for programmable paintings, , colorful-patterned CLC materials, , and rewritable papers …”

“…The PSCLC films can be used as sensors for temperature, 28 humidity, 29 and chemicals. 30 Recent results indicated that they could be used for programmable paintings, 31,32 colorful-patterned CLC materials, 33,34 and rewritable papers. 35 To tune the structural color of PSCLC films, both phase separation 36 and chemical injection techniques 37,38 were developed.…”

Colorfully Patterned Epoxy Resin Films with a Cholesteric Structure Prepared through a Photopolymerization Approach

“…Inspired by this, researchers proposed the concept of photonic crystals to simulate such structural colors. The structural colors produced by the reflection of photonic crystals are highly saturated and resistant to fading. , Cholesteric liquid crystals (CLCs) are widely used to fabricate structural color materials with specific patterns and dynamic responses, − which can be formed by adding a chiral dopant to achiral nematic LCs . The supramolecular helical structure in CLC results in a selective circular polarization reflection on light, also known as Bragg reflection.…”