Preparation of Tough Double- and Triple-Network Supermacroporous Hydrogels through Repeated Cryogelation

Supermacroporous hydrogels, possessing sponge-like structure and permeability, have drawn significant atten-tion for their bioengineering and biomedical applications. However, their mechanical weakness due to their low-density structure is one of their biggest limitations. This work reports a multi-step cryogelation technique, which does not require special equipment, for preparing tough supermacroporous hydrogels on the basis of the double-network (DN) strategy. The produced supermacroporous DN gels possess interconnected pores with pore sizes of 50–230 μm. They also show a com-pressive modulus of up to ~100 kPa, which is 2- to 4-times higher than that of the corresponding supermacroporous single-network (SN) gels, and compressive strength of up to 1 MPa at 80% compression. The supermacroporous DN cryogels are also stretchable with a work of extension of up to 38 kJ m-3, which is 1 to 2 orders larger than that of the SN cryogels. The high stiffness and stretchability distinguish them from other types of cryogels. Supermacroporous triple-network (TN) gels and DN gels composed of different polymer combinations are also prepared. The technique presented herein is suitable for pre-paring supermacroporous DN gels from various polymers; hence, it is promising in meeting bioengineering and biomedical demands.