Polymer-stabilized cholesteric liquid crystal (PSCLC) films have been widely studied for their application as sensors, polarizers, and reflective windows. However, the preparation of programmable and colorful patterns based on the structural color is still challenging. Herein, the photochromic CLC mixtures were prepared by adding a photoisomerizable chiral additive (CA) and a photoinitiator in the nematic liquid crystal LC242. Under UV irradiation with weak intensity, photoisomerization of the CA was carried out and photopolymerization was suppressed by oxygen inhibition. With extending the irradiation time, the helical pitch of the CLC film increased and the selective Bragg reflection band tended to redshift. Under strong UV irradiation, oxygen inhibition was overcome and photopolymerization dominates the reaction. Therefore, the colorful-patterned PSCLC films were able to be prepared using masks. The results shown here not only give us a better understanding of the effect of oxygen inhibition but also lay the foundations for practical applications such as decoration and optical devices.
Structurally colored epoxy resin films were prepared using a liquid crystalline (LC) epoxy monomer of E11M and a chiral additive of CA-iso through a photopolymerization approach. With the addition of the co-photoinitiator isopropyl thioxanthone and comonomer 3′,4′-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate, the polymerization rate was increased. Since the epoxy resin films can be obtained within several seconds, they are feasible for large-area preparation on the coating line. The reflective wavelength was tunable by changing the concentration of CA-iso in the LC mixture. Diffuse-reflectance circular dichroism spectra indicated a right-handed helical supramolecular structure. Field-emission scanning electron microscopy images indicated a multilayer structure. Since the LC mixtures were thermochromic, colorfully patterned epoxy resin films were prepared by controlling the polymerization temperature. Moreover, LC gratings were also prepared, which were expected to be applied for anticounterfeiting.
Circularly polarized luminescence (CPL)-active materials have attracted increasing attention due to their applications in chiral sensing and optoelectronics. However, it is still a challenging task to fabricate CPL materials with large luminescence dissymmetry factors and strong emission intensities in the solid state. In this work, two singlehanded twisted tetraarylethylene (TAE)-bridged polybissilsesquioxane nanotubes have been facilely constructed through a supramolecular templating polymerization of TAE-bridged bis(triethoxysilane) with aggregation-induced emission properties, using self-assemblies of a pair of chiral amino acid-based cationic amphiphiles as the supramolecular templates. It is found that the chirality has been transferred from the self-assemblies to the polybissilsesquioxane nanotubes. The resulting hybrid silicas show high thermal stabilities and bright CPL with the fluorescence quantum yield up to 62.8%.
Polymer-stabilized cholesteric liquid crystal (PSCLC) films with selective circularly polarized light reflection attracted much attention for their applications as polarizers, energy-saving windows and for displays.Herein, CLC mixtures were prepared using a nematic LC LC242 and a chiral compound S-6 with enantiotropic SmA and SmC* phases, which exhibited a cholesteric phase with a smectic order. After photopolymerization, the PSCLC films with fingerprint structure at the surfaces and supramolecular helical structure inside were obtained. Due to the existence of short-range smectic order in the cholesteric structure, the Bragg reflection bands were broadened.For a CLC mixture, with increasing temperature, the short-range smectic order was suppressed, and the selective Bragg reflection band shifted to the short wavelength. Based on this thermochromic behavior, colorful PSCLC patterns and gratings were prepared, which were able to be applied in decoration and anti-counterfeiting. Since the PSCLC films can be obtained within several seconds under air, large-area films can be prepared on coating lines in lowcost.
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