Facile Fabrication of Robust Hydroelastomers via Synergistic Osmotic Pressure and Metal-Coordination Bonding

Elastomers are vital for applications demanding flexibility and resilience, yet an inherent trade-off between strength and toughness generally exists in conventional systems. Here, we present a facile strategy to fabricate robust poly(acrylic acid) (PAA)-based hydroelastomers by synergizing osmotic pressure and dynamic metal-coordination bonding. In the design, a slightly crosslinked PAA hydrogel is immersed in a concentrated FeCl₃ solution, where external osmotic pressure rapidly dehydrates the network, achieving ultrahigh polymer chain density. Concurrently, Fe³⁺ ions penetrate the matrix, forming dynamic -COO^-•••Fe³⁺ coordination bonds that enhance energy dissipation and cohesion. Systematic studies are carried out to understand the effects of metal-ion concentration and monomer concentration on the mechanical properties of the hydroelastomers. The resulting hydroelastomers retain ≈10 wt.% water, enabling flexibility while exhibiting unprecedented mechanical properties: Young's modulus >100 MPa, tensile strength >9 MPa, work of extension >38 MJ m^-3, fracture energy >35000 J m^-2, and elongation at break >400%, alongside optical transparency. These properties surpass those of many commercial elastomers (e.g., PDMS, natural rubber). Furthermore, the hydroelastomers demonstrate reversible softening upon rehydration, facilitating stimuli-responsive applications. This work offers a simple yet effective strategy for designing and fabricating robust elastomers that harmonize strength, toughness, and elasticity.