Tough Semi-interpenetrating Polyvinylpyrrolidone/Polyacrylamide Hydrogels Enabled by Bioinspired Hydrogen-bonding Induced Phase Separation

Semi-interpenetrating (semi-IPN) hydrogels formed by the continuous interpenetration of cross-linked polymer network and linear non-crosslinked polymer with multifunctionality are widely used in biomedical and other fields. However, the negative impact of linear polymer on the homogeneity of the cross-linked network often leads to a decrease in the mechanical properties of semi-IPN hydrogels and severely limits their applications. Herein, a bioinspired hydrogen-bonding induced phase separation strategy is presented to construct the tough semi-IPN polyvinylpyrrolidone/polyacrylamide hydrogels (named PVP/PAM hydrogels), including the linear polymer polyvinylpyrrolidone (PVP) and cross-linked polyacrylamide (PAM) network. The resultant PVP x /PAM hydrogels exhibit unique phase separation induced by the hydrogen bonding between PVP and PAM and affected by the amount of substance of PVP. Meanwhile, the phase separation of PVP x /PAM hydrogels results in excellent mechanical properties with a strain of 2590%, tensile strength of 0.28 MPa and toughness of 2.17 MJ/m 3 . More importantly, the hydrogen bonding between PVP and PAM firstly disrupts to dissipate energy under external forces, so the PVP x /PAM hydrogels exhibit good self-recovery properties and outperform chemically cross-linked PAM hydrogels in impact resistance and damping applications. It is believed that the PVP x /PAM hydrogels with hydrogen-bonding induced phase separation possess more potential application prospects.