Heterotypic Supramolecular Hydrogels.

Supramolecular hydrogels, formed via intermolecular interactions in water, are emerging as a new type of versatile soft materials to be applied in many areas, such as biomedical applications, catalysis, food additives, and cosmetics. While most of the supramolecular hydrogels are homotypic (i.e., one type of building blocks), heterotypic supramolecular hydrogels are less explored, but may offer unique advantages. This review discribes supramolecular hydrogels that consist of more than one type building blocks (i.e., heterotypic) to illustrate the promises and challenges of heterotypic supramolecular hydrogels as soft biomaterials. First, we discuss the driving force for producing heterotypic supramolecular hydrogels. Second, we introduce the general methods for triggering heterotypic supramolecular hydrogels. Third, we summarize the examples of heterotypic supramolecular hydrogels made of hydrogelators with or without containing amino acid residues. Fourth, we describe the applications of heterotypic supramolecular hydrogels up-to-date. Finally, we give the outlook and propose a few future directions that likely worth to be explored.