MoS<sub>2</sub>-loaded cholesteric liquid crystal microcapsules for NIR responsive thermochromism.
basic_science · Level V
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- Record sourced from PubMed, PMID 42446060.
- Also identified by DOI 10.1039/d6lc00283h.
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Abstract
Thermochromic materials with temperature-dependent color changes and color memory are widely used in functional coatings, anti-counterfeiting, and smart architectures. Cholesteric liquid crystal (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 (MoS<sub>2</sub>)-doped double emulsion droplets with CLC as the 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% MoS<sub>2</sub>-doped CLC show approximately 3-fold reduction in total response time from 19.0 ± 2.35 s to 6.2 ± 0.84 s and an increase in excitation purity from 0.16 ± 0.03 to 0.55 ± 0.05. By tuning molecular arrangement <i>via</i> entropic and enthalpic effects and enhancing thermal transport <i>via</i> heat conduction, MoS<sub>2</sub> mitigates the thermal resistance of the polymer shell, leading to a rapid thermochromic response. Additionally, MoS<sub>2</sub> boosts color saturation and enables NIR photothermal chromism <i>via</i> broadband absorption. The NIR-TCM films display static patterns at room temperature, while they create new visible patterns <i>via</i> 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.