Cu⁺-containing physically crosslinked chitosan hydrogels with shape memory

Physically crosslinked chitosan hydrogels have better biocompatibility and possess unique functional characteristics but suffer from poor mechanical properties. In the current study, we prepared Cu⁺-containing physically crosslinked chitosan hydrogels by exploiting ammonia fumigation and reduction of Cu²⁺ by NaHSO₃. The content of Cu⁺ in the prepared hydrogels was in a low range of 4.88–29.27 μmol/g. The mechanical strength of the CTS-Cu⁺/NH₃ hydrogels was remarkably improved up to 0.25 MPa and the elongation at break increased with rising content of Cu⁺ due to the dynamic crosslinks between chitosan and Cu⁺. Moreover, the CTS-Cu⁺/NH₃ hydrogels demonstrated evident shape memory after exposure to air by exploiting the different coordination number of Cu²⁺ and Cu⁺. Thus, the prepared hydrogels may have good potential applications as biomedical materials.