Incorporating polymers within a single-crystal: From heterogeneous structure to multiple functions

Single-crystals, commonly considered as homogeneous solids, are able to be internally interfaced abnormally with guest polymers, which can be found in the biominerals where single-crystals incorporate surrounding biomacromolecules to reinforce their mechanical properties. This unique feature combining heterogeneous structure and long-range atomic ordering have attracted abundant investigations of reproducing their synthetic analogs to expand the potential application scope. Here, we summarize the recent progresses in the synthetic single-crystal composites, where polymer guests are incorporated inside single-crystals to generate heterogeneous structures without interruption to the long-range ordering of crystal hosts. First, the uniform and patterned encapsulations inside the various single-crystals are concluded in the sequence of isolated and continuous polymer-based guests. In addition, the mechanisms are classified chemically and physically, and the corresponding controlled factors that govern the incorporation processes are discussed. Most importantly, typical attempts on the applications of these heterogeneous single crystals are introduced, including mechanical reinforcement, bandgap engineering, catalyst, self-healing, controlled release, and optoelectronic devices. We aim at stressing on the current and potential applications benefited from the unique structural properties of the polymer incorporated single-crystals, and accordingly propose the perspectives to accelerate the path from the structural analysis toward prosperous functions.