Microdroplets made from chiral liquid crystals (CLCs) can display reflective structural colors. However, the small area of reflection and their isotropic shape limit their performance. Here, Janus microdroplets are synthesized through phase separation between CLCs and silicone oil. The as‐synthesized Janus microdroplets show primary structural colors with ≈14 times larger area compared to their spherical counterparts at a specific orientation; the orientation and thus the colored/transparent states can be switched by applying a magnetic field. The color of the Janus microdroplets can be tuned ranging from red to violet by varying the concentration of the chiral dopant in the CLC phase. Due to the density difference between the two phases, the Janus microdroplets prefer to orientate the silicone oil side up vertically, enabling the self‐recoverable structural color after distortion. The Janus microdroplets can be dispersed in aqueous media to track the configuration and speed of magnetic objects. They can also be patterned as multiplexed labels for data encryption. The magnetic field‐responsive Janus CLC microdroplets presented here offer new insights to generate and switch reflective colors with high color saturation. It also paves the way for broader applications of CLCs, including anti‐counterfeiting, data encryption, display, and untethered speed sensors.

Liquid crystal-nanoparticle (LC-NP) hybrid systems allow synergistic interactions between LC matrixes with anisotropic alignment and NP dopants with versatile functionalities. A uniform, well-dispersed, and highly stable thermotropic LC-NP mixture paves the way for further applications. In this work, a linear promesogenic ligand and two types of dendritic promesogenic ligands with alkyl or oligo ethylene glycol (OEG) chains are designed and synthesized to facilitate incorporating NPs into the thermotropic 4-cyano-4′-pentylbiphenyl (5CB) LC matrix. A comparison study between the linear and the dendritic ligands on the capability to promote miscibility and stability of NPs in LCs is conducted. Miscibility test results show that the linear ligand and the OEG-chained dendrimer both perform well in uniformly dispersing NPs in LCs. Dynamic assemblies of NPs assisted by dendritic ligands and driven by aligning and equilibrating of mesogens are captured, showing the potential of manipulating the assembly of NPs through external thermal stimuli. The stability test shows that both types of dendrimers can significantly enhance the shelf-life time and thermal stability of NPs compared to the linear ligand. In particular, Au NPs capped with OEG-chained dendrimers are stable in 5CB for 6 months at room temperature and over 10 h at 50 °C. The synthesis of dendritic ligands is highly modulated and can be generalized onto NPs with different dimensions and properties. Tied by the dendritic promesogenic ligands, this LC-NP hybrid system with good uniformity and stability could be further applied to tunable optical displays, responsive materials, etc.

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