Toward the Synthesis of Nanoparticles‐Hydrogel Composites by Magnetron Sputtering onto Liquids and Subsequent Photopolymerization

We report a strategy for fabricating ultra‐pure nanoparticles–hydrogel composites by combining low‐pressure plasma‐based magnetron sputtering onto liquids with subsequent free radical photopolymerization. In a first step, various photocurable host liquids were screened for vacuum compatibility, viscosity, and stability under plasma exposure, highlighting poly(ethylene glycol) methyl ether acrylate (PEGMEA) as the most suitable candidate. A copper target was accordingly sputtered by an argon plasma onto PEGMEA, yielding stable colloidal suspensions of monomodal copper oxide (CuO) nanoparticles with a radius of 1.23 ± 0.015 nm. Careful outgassing procedure and sputtering conditions are critical to prevent undesired plasma‐induced reactions (e.g., premature polymerization). The total copper concentration was controlled by adjusting the deposition time and sputtering power during sputtering. Further addition of polyethylene glycol diacrylate crosslinker and diphenyl(2,4,6‐trimethylbenzoyl)phosphine oxide photoinitiator into the CuO NPs–PEGMEA colloids enables ex situ near‐UV photopolymerization to form transparent nanoparticles‐hydrogel composites. The composites contain small particles (7.38 ± 0.32 nm), and larger aggregates (67.47 ± 0.53 nm). Characterization by SEM, TEM, UV–vis spectrophotometry, photo‐rheology, and x‐ray absorption near‐edge spectroscopy confirmed the nanostructure and composition of the materials. This work opens new opportunities for developing surfactant‐free NP/hydrogel composites compatible with manufacturing techniques such as 3D printing.