MoS2 Loaded Cholesteric Liquid Crystal Microcapsules for NIR Responsive Thermochromism

Abstract

Thermochromic materials with temperature-dependent color changes and color memory are widely used in functional coatings, anti-counterfeiting, and smart architectures. Cholesteric liquid crystals (CLC) molecules undergo periodic helical twisting of their orientation, forming a unique helical superstructure with fluidity and long-range orientational order. When confined in microscale spherical droplets with interfacial anchoring, CLC assemblies exhibit dynamic optical response due to thermoresponsive molecular rearrangement. The helical defects within physical confinement and the interfacial molecular anchoring jointly interfere with the cholesteric reorganization, offering intelligent color modulation and structural stability but with limited color saturation and slow response. Herein, we construct molybdenum disulfide (MoS2) doped double emulsion droplets with CLC as core using droplet microfluidics, creating near-infrared-activated thermochromic microcapsules (NIR-TCMs) with enhanced response and color saturation. The microcapsules with controllable diameters (75.4-275.0 μm) and shell thicknesses (9.7-43.0 μm) are formed by polymerizing the middle phase of the double emulsion droplets. NIR-TCMs (136 μm core, 16 μm shell) of 0.5 wt% MoS2 doped CLC show approximately 3-fold reduction in total response time from 19.0 ± 2.35 s to 6.2 ± 0.84 s and increase in excitation purity from 0.16 ± 0.03 to 0.55 ± 0.05. By tuning molecular arrangement via entropic and enthalpic effects and enhancing thermal transport via heat conduction, MoS2 mitigates the thermal resistance of the polymer shell, leading to a rapid thermochromic response. Additionally, MoS2 boosts color saturation and enables NIR photothermal chromism via broadband absorption. The NIR-TCM films display static patterns at room temperature, while they create new visible patterns via NIR excitation. These patternable NIR-TCMs enable remote modulation of the optical properties of individual microcapsules and the overall device, offering a photonic chip for information encryption and optical coatings.