Thermo- and pH- dual responsive inorganic-organic hybrid hydrogels with tunable luminescence

A thermo- and pH- dual responsive luminescent hydrogel was successfully constructed by coupling dysprosium-containing polyoxometalates Na9DyW10O36 (DyW10) with the ABA triblock copolymer, where the B block is PEO and the A block is the thermosensitive poly(methoxydi(ethylene glycol) methacrylate-co-N,N-dimethylaminoethyl methacrylate). The complex hybrid underwent a sol-gel phase transition above the lower critical solution temperature (LCST) of the A block. DyW10 was electrostatically encapsulated into the hydrophobic domain of the A block with enhanced photoluminescence. When temperature cooled down, the luminescence could be restored. By addition of acids to protonate the A block, and emission of DyW10 was simultaneously enhanced. Sensitivity of poly(N,N-dimethy laminoethyl methacrylate) (PDMAEMA) to pH also enabled the emission of DyW10/copolymer hydrogel to be reversibly switched by alternating acid/base treatments.