Sodium alginate crosslinker engineered UCST hydrogel towards superior mechanical properties and controllable dye removal.

Smart hydrogels that can adsorb both anionic and cationic dyes and have excellent mechanical properties have not been reported yet, despite bright prospect in dye adsorption. The emergence of polyampholyte made it possible for the preparation of novel hydrogels. PMAD (copolymer of AM, AA and DMC) is a novel thermo-responsive hydrogel based on polyampholyte, whereas poor mechanical properties limit its application. Herein, we designed a novel polysaccharide crosslinker, which integrates chemical-crosslinking network and physical-entanglements to fabricate PMAD hydrogels. Chemical-crosslinking network maintains the shape of hydrogel as backbone, whereas physical-entanglements enhance the energy-dissipation capacity by disentangle upon deformation. Synergistic effect of the above structure improves the fracture strength and elongation of PMAD by nearly 4700% and 900%, respectively. Moreover, the hydrogel can be used as controllable adsorption material towards both cationic and anionic dyes, which could greatly increase adsorption capacity after reaching the critical temperature due to its unique temperature-sensitive characteristics.