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

Supermacroporous hydrogels, possessing a spongelike structure and permeability, have drawn significant attention for their bioengineering and biomedical applications. However, their mechanical weakness due to the low-density structure is one of their biggest limitations. This work reports a multistep 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 compressive modulus of up to ∼100 kPa, which is 2–4 times higher than that of the corresponding supermacroporous single-network (SN) gels, and a 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 1–2 orders larger than that of the SN cryogels. Their 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 preparing supermacroporous DN gels from various polymers; hence, it is promising in meeting bioengineering and biomedical demands.