Why are double network hydrogels so tough?

Double-network (DN) gels have drawn much attention as an innovative material having both high water content (ca. 90 wt%) and high mechanical strength and toughness. DN gels are characterized by a special network structure consisting of two types of polymer components with opposite physical natures: the minor component is abundantly cross-linked polyelectrolytes (rigid skeleton) and the major component comprises of poorly cross-linked neutral...