Lanthanide-based hydrogels with adjustable luminescent properties synthesized by thiol-Michael addition

Luminescent hydrogels have been widely used in many fields because of their excellent optical properties. Although there are many mature preparation methodologies, the development of new luminescent hydrogels with adjustable fluorescence properties and good mechanical properties is still an urgent need to explore. In this paper, we describe a simple and effective way to synthesize highly luminescent PVA/AM-Ln(DPA)(3) double network hydrogels by thiol-Michael addition reaction and in situ polymerization. We firstly synthesized a bifunctional chelating ligand named as 4-(mercaptomethyl)pyridine-2,6-dicarboxylic acid, which can react with electron-deficient carbon-carbon double bonds and effectively sensitize the luminescence of Tb3+ and Eu3+ ions. And then, the luminescent lanthanide complexes were grafted onto the methacrylated polyvinyl alcohol via thiol-Michael addition reaction. Finally, the modified polymers were polymerized with acrylamide monomer to form the luminescent double network hydrogels. The obtained hydrogels possess bright luminescence, long luminescence lifetimes and good mechanical properties. Moreover, the emission colors of the hydrogels are adjustable by varying the molar ratio of Eu3+ and Tb3+.