A novel strategy inspired by Luban lock towards endowing polyzwitterionic electrolyte hydrogel with UCST behaviors

The electrostatic interaction in polyzwitterionic electrolyte hydrogels is the prerequisite for materials to exhibit temperature-sensitive behaviors. Few reports mention the potential temperature-sensitive properties of these hydrogels, although amounts of polyzwitterionic electrolyte hydrogels with bright prospects in advanced fields have been reported. PMAD (copolymer of AM, AA and DMC) is a typical polyzwitterionic electrolyte, which is taken as an example to elucidate the essential conditions for the UCST behaviors of polyzwitterionic electrolyte hydrogels. The temperature-sensitive properties of PMAD hydrogels depends on the tight stacking of zwitterionic polymer chains, while the introduction of chemical crosslinker could limit the movement of PMAD chains and increase the difficulty of forming effective electrostatic interactions between zwitterionic segments resulting in the disappearance of UCST behaviors. Accordingly, the strategy inspired by the Chinese Luban lock for compressing the distance of PMAD chains by utilizing the “mortise-tenon” structure could recovery the UCST behaviors of PMAD and are expected to endow more polyzwitterionic electrolyte hydrogels with temperature-responsive properties. • The essential conditions for the UCST behaviors of polyzwitterionic electrolyte hydrogels were proposed: the temperature-sensitive properties of PMAD hydrogels depends on the tight stacking of zwitterionic polymer chains. • Physically crosslinked PMAD hydrogels synthesized from high monomer concentration could exhibit UCST behaviors in which PMAD chains could be freely stacked. • The introduction of chemical crosslinker could limit the movement of PMAD chains and increase the difficulty of the association between the anionic and cationic segments resulting in difficulty in forming effective electrostatic interactions. • A novel strategy inspired by Luban lock towards endowing polyzwitterionic electrolyte hydrogel with UCST behaviors was proposed. • The strategy of endowing the hydrogel UCST behavior with “mortise-tenon” structure of DN hydrogels is expected to endow more polyzwitterionic electrolyte hydrogels with temperature-responsive properties, thus greatly broadening the range of UCST hydrogels.