writer：Dandan Wei, Jia Yang* , Lin Zhu, Feng Chen, Ziqing Tang, Qin Gang, Qiang Chen*
keywords：double network hydrogels
source：期刊
specific source：Polymer Testing
Issue time：2018年
Double network hydrogels (DN gels) are one of most extensively investigated high strength hydrogels. However, conventional DN gels are fully chemically cross-linked, which often suffer from severe softening phenomenon and are lack of self-healing properties. In the present work, fully physically cross-linked Agar/PAAm DN gels, consisting of physical agar gel as the first network and physical polyacrylamide (PAAm) gel as the second network, were prepared by the “one-pot” method, in which both of the networks are cross-linked by hydrogen bonds. It was found hydrogen-bonds cross-linked and high mechanical PAAm physical single network (SN) gel as well as Agar/PAAm physical DN gel should be prepared at a high AAm concentration (50?wt%). At optimal condition, Agar/PAAm physical DN gel achieved E of 498?kPa, σf of 0.48?MPa,εf of 24.11?mm/mm and W of 10.24?MJ/m3, which was much better than those of PAAm physical SN gel (E of 355?kPa, σf of 0.24?MPa, εf of 23.3?mm/mm and W of 5.82?MJ/m3). Both of Agar/PAAm physical DN gel and PAAm physical SN gel exhibited large hysteresis loops. Agar/PAAm physical DN g els also demonstrated rapid self-recovery (～83% toughness recovery for 2?min resting) at room temperature without external stimuli. Different from Agar/PAAm hybrid DN gels with negligible self-healing property, Agar/PAAm physical DN gels exhibited obvious self-healing property, and the healed gel could achieve tensile strength of 0.38?MPa (healing efficiency ～75%) and tensile strain of 420%. Combination of high strength, rapid self-recovery, and self-healing performances, fully physical Agar/PAAm DN gels hold promising for potential bio-applications under physiological conditions.