Ultrastrong and Tough Anisotropic Organogel via Alignment-Induced Densification and Glycerol Plasticization

Polymer gels, such as hydrogel and organogel, are widely used in tissue engineering, biomedicine, and flexible electronic devices due to their good compatibility and environmental stability. However, it is still a great challenge to achieve simultaneous high strength, toughness, and elongation to meet the demands of different applications. Herein, this work proposes a strategy involving freeze-thawing, stretch-drying and thermal annealing in glycerol to fabricate ultrastrong and tough polyvinyl alcohol (PVA) organogel with anisotropic microstructure. Freeze-thawing cycles push PVA chains together through the formation of ice crystals, facilitating the entanglement of polymer chains and the formation of hydrogen bond network. Directional stretch-drying process induces molecular chain orientation and enhances the intermolecular interactions. Thermal annealing (TA) in glycerol promotes chain rearrangement and densifies the cross-linking of hydrogen bond network, which synergistically enhances strength and toughness. The prepared anisotropic PVA organogel exhibits extraordinary toughness of 416 $\mathrm{MJ}/m^3$ , excellent strength of 61.14 MPa, and fracture strain of 961%. Simultaneously, the organogel has high optical transparency ( $\sim 90\%$ ) and superior stability in sub-zero conditions. This work provides a novel and effective strategy for fabricating ultrastrong and tough organogel, offering promising potential applications in bionic tendons for soft robotics and transparent protective shields.