Hydrogels and elastomers can reversibly change their size and shape under different conditions. This property makes them attractive for a wide variety of applications, including artificial muscles, drug delivery, and sensors. But they have not yet been commercialized for applications as they are usually weak and brittle.We are designing films, elastomers, and hydrogels with environmental sensitivities that are extremely stretchable as well as mechanically strong by introducing supramolecular polyrotaxane cross-linkers into the polymer network. The improvements mark an important step toward enabling hydrogels to reach their full commercial potential. Additionally, fast stimuli-sensitive polymeric materials that exhibit reversible changes in their selective permeability to molecules, surface wettability, and ability to convert chemical energy into mechanical energy are trying to use them as drug delivery systems, artificial muscles, and sensors.