Shear-Thinning Hydrogel Precursors for High-Loading X-ray Shielding Coatings with Superior Mechanical Performance

With the rapid advancement of radiation technology in nuclear safety, industrial inspection, and medical applications, there is a growing and urgent demand for biocompatible radiation-shielding coatings. This study addresses the challenge of filler sedimentation at high loadings by utilizing a shear-thinning precursor. This precursor, comprising acrylamide (AM), cross-linker, thermal initiator, sodium alginate, and hyaluronic acid, exhibits liquid behavior under shear but solidifies without force due to dynamic Fe³⁺-carboxyl coordination cross-linking facilitated by an Fe³⁺-EDTA complex. This property enables the homogeneous dispersion of high-content X-ray shielding fillers (Bi₂O₃ and BaSO₄) within the precursor and allows for its uniform coating onto substrates with complex geometries. Subsequent thermal curing initiates polymerization of AM, forming a covalently cross-linked polyacrylamide second network, resulting in a robust double-network composite hydrogel. Systematic investigation revealed that a hydrogel containing 40 wt % Bi₂O₃ and BaSO₄ achieved optimal X-ray shielding performance. With a 5 mm thickness, it attained complete attenuation of X-rays below 80 kV and achieved 92.2% shielding efficiency at 100 kV. Meanwhile, it exhibits excellent mechanical properties, stretching to 2000% of its original length while maintaining a stress of 1.30 MPa. Furthermore, the developed hydrogel coating demonstrated favorable biocompatibility and antibacterial properties, supporting its potential for biomedical applications.