Janus Hollow Microstructures via an Interfacial Phase Hydrogen Bond Network

Abstract Janus hollow microstructures have been widely used in chemistry, medicine, biology, and materials science because of their anisotropy and hollow structure. Constructing multiple types of hollow microstructures and establishing structure‐property relationships remain challenging. Here, the present authors develop a one‐pot polymerization strategy for constructing Janus hollow microstructures in which deep eutectic solvents (DESs) completely replace water as the continuous phase. A range of Janus hollow microstructures are produced with various compositions, as well as various ratios of the hydrophilic part and film thickness. Consequently, their corresponding morphologies range from 3D‐like forms (such as spherical and bowl shapes) to 2D‐like forms (including pie shapes, vesicle shapes, and vacuum‐bag‐like). There are hydrogen bond interactions between the DESs and hydrophobic monomers at the DES‐oil interface. The presence of free radicals at the interface has also been demonstrated. Hence, hydrogen bond networks formed at the DES–oil interfacial phase, inducing monomer activation and radical stabilization at the DES‐St interface during the polymerization, which is the underlying mechanism for forming the Janus hollow structure. The polymerization strategy provides a faster, more convenient, and more universal way to prepare Janus hollow microstructures compared with conventional methods.