Anisotropic thermoresponsive hydrogels by mechanical force orientation of clay nanosheets

Hydrogels have drawn great attentions in the past two decades due to their excellent biocompatibility and multi stimuli responsiveness, which have a wide range of applications in the field related to tissue engineering, sensor and biomedicine. However, conventional artificial hydrogels are usually isotropic in structure with random crosslinking of polymer chains. To imitate the well-defined hierarchical structures ranging from the molecular scale to macroscopic scale like biological soft tissues in hydrogels. Herein, an anisotropic thermoresponsive hydrogel was reported via a linear remolding of highly stretchable clay-PNIPAm nanocomposite hydrogel by a secondary crosslinking. The as-prepared hydrogel shows anisotropic mechanical performance and can deformed anisotropically in response to temperature change. Besides, the oriented structures of clay nanosheets and polymer network that contribute to understand the anisotropic mechanism of SC-hydrogel was investigated. The special functions of current SC-hydrogel suggest that it may serve as ideal composite gel materials with validity in a variety of applications, such as soft actuators, sensors, and biological materials.