Epoxy polymers as versatile hydrophobic components for tough phase-separated hydrogels

The inherent paradox between hydrophilicity and hydrophobicity poses significant challenges for introducing hydrophobic components into hydrogels to achieve controlled phase separation. This work presents a solution using hydrophobic epoxy polymers (EPI) containing polar groups, which enable the fabrication of a non-covalent bond crosslinked hydrogel with microphase separation. The resulting hydrogels possess exceptional mechanical properties, including a tensile strength of 14.15 MPa and a Young's modulus of 295.87 MPa, through water-induced phase separation and glass transition of the EPI. The high glass transition temperature of the EPI enables temperature-tunable mechanical properties and imparts shape-memory functionality to the gels. The hydrophilic component can also include other hydrogen bond-forming polymers, such as polyacrylic acid or polyvinylpyrrolidone. This work provides a versatile hydrophobic component for phase-separated hydrogels, which gives a new idea for the design of tough and multi-functional hydrogels with tailored properties.