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

Abstract

Supermacroporous hydrogels, possessing sponge-like structure and permeability, have drawn significant attention 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 compressive modulus of up to ~100 kPa, which is 2-to 4-times higher than that of the corresponding supermacroporous singlenetwork (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 preparing supermacroporous DN gels from various polymers; hence, it is promising in meeting bioengineering and biomedical demands.

Multifunctional Liquid‐Free Ionic Conductive Elastomer Fabricated by Liquid Metal Induced Polymerization

“…It is comparable to other reported liquid‐free elastomer [ 2 ] and much higher than that of hydrogel‐based ionic conductors (Figure S22, Supporting Information). [ 18,24 ] What's more, they exhibited high stretchability even exposed to −40 °C for days (Figure S23, Supporting Information).…”

“…[ 18–20 ] Additionally, most synthetic networks involved long heating steps (or ultraviolet radiation) and toxic crosslinkers addition. [ 21–24 ] Thus, the fabrication processes are complex and time consuming. Moreover, autonomous self‐healing conductive elastomers have been rarely reported due to the difficulty of locating dynamic bonds in the liquid‐free polymer network.…”

Supplementary Networking of Interpenetrating Polymer System (SNIPSy) Strategy to Develop Strong & High Water Content Ionic Hydrogels for Solid Electrolyte Applications

“…[ 7 ] Several strategies have so far been utilized in literature to enhance the toughness of hydrogels. Mainly, double & triple networking, [ 8,9 ] interpenetration of polymer networks, [ 10 ] reinforcement of hydrogels via nanoparticles, [ 11 ] incorporation of energy dissipating physical & chemical linkages, [ 12,13 ] network alignment, [ 14 ] and slide ring networks [ 15 ] approaches have so far been successful to develop tough and stretchable hydrogels. For example, the exemplary first report on double networking approach improved the compressive strength of hydrogels up to 17 megapascal (MPa) and fracture toughness at high water content of ≈90%.…”

“…[7] Several strategies have so far been utilized in literature to enhance the toughness of hydrogels. Mainly, double & triple networking, [8,9] at the interface substantially improved the performance of anode through retention of electrode-electrolyte interface via device integrity and sustained mechanical durability, while maintaining adequate ionic conductivity. [24] Moreover, non-flammable and safe electrolyte systems are considered to be one of the prime objectives of the next generation of rechargeable batteries, which the hydrogel-based aqueous electrolyte systems are capable to address.…”

Biocompatible and Enzymatically Degradable Gels for 3D Cellular Encapsulation under Extreme Compressive Strain

“…This low strain level is in part due Gels 2021, 7,101 to the fact that common cytocompatible polymer hydrogels such as alginate and gelatin methacryloyl (GelMA), along with certain explanted soft tissues, typically fail at or below 50% compressive strain [22][23][24]. In contrast, existing hydrogels optimized for very high toughness and strain tolerance are frequently unsuitable for cell encapsulation due to toxic components or inhospitable gelation conditions [25][26][27]. This limitation presents a need for hydrogel scaffolds optimized for bulk compression of encapsulated cells at very high strain.…”