Preparation and catalytic properties of modified PGMA-based pH-responsive hydrogel films as a novel template for in situ synthesis of Au, Ag, and Au:Ag nanoparticles

Metal-nanoparticle (M-NP)-modified glycidyl methacrylate (GMA)-based hydrogel film composites were synthesized and assessed for their catalytic activities by reducing para-nitrophenol (p-NP) to para-aminophenol (p-AP) with sodium borohydride. Poly(ethylene glycol)methyl ether-block-poly(glycidyl methacrylate)-block-poly(methyl methacrylate) (MPEG-b-PGMA-b-PMMA) triblock copolymer was synthesized via atom transfer-radical polymerization. The epoxy ring of the PGMA blocks was opened by the addition of 1-methylpiperazine. The resulting bifunctional polymer containing 2-hydroxy-3-methyl piperazinepropyl methacrylate units was used to synthesize novel crosslinked hydrogel films by quaternization of the tertiary amine (methylpiperazine) with 1,2-bis(2-iodoethoxy)ethane. The synthesized hydrogel film swelled in aqueous solution when the pH was changed from basic to acidic. The prepared MPEG-b-PHMPPMA-b-PMMA hydrogel film was used as an immobilizing matrix to form monometallic silver (Ag) and gold (Au) and bimetallic alloy gold:silver (Au:Ag) nanoparticles. The M-NP/hydrogel film composites were characterized by transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, and ultraviolet-visible spectrophotometry. The synthesized M-NP/hydrogel film composites showed good catalytic activity to reduce p-NP to p-AP. The composites were also found to be reusable as their activity only slightly dropped after 10 consecutive uses. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48360.