Effect of Structural Features of Polymer Gels Containing Au Nanoparticles on Their Catalytic Properties

Abstract

Au(0) nanoparticles catalyze many reactions and various Au-polymer composites have been developed to date. Herein, we developed different types of Au(0)-nanoparticle-loaded gels and investigated the effects of their structural features such as the polymer type, gel diameter, and gel composition on their catalytic properties. N-isopropylacrylamide (NIPA) gel, N,N-dimethylacrylamide (DMAA) gel, poly(ethylene glycol) diacrylate (PEGDA) gel, and poly(ethylene glycol) methyl ether acrylate (PEGMEA) gel were used, and millimeter-, micrometer-, and nanometer-sized gels were fabricated. Au(0)-nanoparticle-loaded gels were obtained by adsorbing Au(III) ions onto the gels, followed by the reduction of the adsorbed ions. All the Au(0)-nanoparticle-loaded gels successfully functioned as catalysts for the reduction of p-nitrophenol to p-aminophenol with NaBH₄. The catalytic performance of the gels was evaluated using the pseudo-first-order reaction rate constant and apparent activation energy. The polymer type and the DMAA gel composition had little effect on the apparent reaction rate constant. The kinetic rate-determining steps in the Au(0)-nanoparticle-loaded gels with various diameters were identified using the Weisz–Prater modulus and the effectiveness factor, and the concentration profile of the reactant in the gels were estimated.