Transparent, UV-proof and mechanically strong montmorillonite/alginate/Ca²⁺ nanocomposite hydrogel films with solvent sensitivity

Fully swollen montmorillonite/alginate/Ca²⁺ (Ca²⁺-MtAlg) nanocomposites with a specific chemical composition are expected to show well-ordered microstructure, excellent mechanical properties, unique optical properties and solvent sensitivities. Inspired by nacre, Ca²⁺-MtAlg nanocomposite hydrogel films with high montmorillonite mass contents (≥ 20%) were synthesised by solution casting, followed by subsequent ionic crosslinking. The fully swollen Ca²⁺-MtAlg nanocomposite films were mechanically flexible and stable in water. By regulating the relative content of alginate and Mt, it was possible for the hydrogel films to reach a high tensile strength of 28 MPa. Ca²⁺-MtAlg hydrogel films also showed acceptable transparency and high efficiency in blocking ultraviolet light. Furthermore, they demonstrated solvent sensitivity; the hydrogels lost water in either methanol or acetone, the one with an Mt/Alg mass ratio of 1:4 coiled seriously in acetone while those with a lower mass ratio were more stable in either methanol or acetone. Overall, Ca²⁺-MtAlg nanocomposite hydrogel films have the potential for use in stimuli-responsive load-bearing biomedical applications, skin care and beyond.