Preparation and characterization of mechanically robust and thermo-responsive hydrogel inspired by spring-like structure

Poor mechanical properties of PMAD (the copolymer of AM, AA and DMC) hydrogel derived from its highdensity rigid crosslinking structure is main obstacle for its functional application. Herein, inspired by springlike structure, nano-SiO2 based crosslinker was used to fabricate mechanical robust thermo-responsive PMADmatrix hydrogel. Nano-SiO2 was modified with poly (ethylene imine) (PEI), which was further introduced in crosslinking network of PMAD hydrogel. Flexible PEI chains can elongate under stress, which endows crosslinking network deformability, like that of spring in tension. Meanwhile, nano-SiO2 can improve the tensile strength of the hydrogel, and amino groups in PEI can improve its dispersity in water. When content of the crosslinker is 15 parts per thousand, tensile strength and elongation at break can be improved by nearly 3540% and 503% respectively owing to synergistic effect of PEI and SiO2. More interesting, mechanical properties of hydrogels can be designed flexibly by controlling the structure of the nano-SiO2 based crosslinker, which realizes structure management of hydrogel. Moreover, hydrogel prepared by this method also shows thermo-responsivity, endowing it potential for functional application.