Thermal and pH Dual Responsive Copolymer and Silver Nanoparticle Composite for Catalytic Application

N-Isopropylacrylamide and vinyl imidazole copolymer, P(NIPAM-co-VI), was synthesized by free radical emulsion polymerization. Then, the copolymer and silver nanoparticle composite, P(NIPAM-co-VI)-Ag, was prepared by in situ reduction of AgNO3 with NaBH4. Due to the coexistence of thermal-responsive PNIPAM and pH-responsive PVI, P(NIPAM-co-VI) and P(NIPAM-co-VI)-Ag exhibited both thermal and pH responsibility, their size would change while altering the temperature or pH of the circumvent. Their thermal and pH dual responsive properties were studied by dynamic light scattering (DLS). P(NIPAM-co-VI)-Ag could be stably dispersed in water at a pH range from 3.0 to 9.3, which is favorable to use P(NIPAM-co-VI)-Ag as a catalyst in the reduction reaction of p-nitrophenol. The reaction rate constant (k(app)) increased with the decrease of pH or the increase of VI content in the copolymer.