Poly(styrene-co-N-isopropylacrylamide)/poly(N-isopropylacrylamide) [P(St-NIPAM)/PNIPAM] composite microgels with core-shell structures were synthesized by two-step reaction including a surfactant-free emulsion polymerization and a seed emulsion polymerization method. P(St-NIPAM)/PNIPAM composite microgels were fully swollen in AgNO₃ aqueous solution. Using alcohol as reducing agent, P(NIPAM-St)/PNIPAM-Ag composite microgels loaded with Ag nanoparticles were prepared in the atmosphere of ammonia gas via polymer microgel template technique. The structures, components and properties of the prepared composite microgels were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), UV-visible spectrophotometer (UV-vis) and laser particle size analyzer. It was demonstrated that P(St-NIPAM)/PNIPAM-Ag also showed thermosensitivity, and the thermosensitivity was weaken with the inceasing of the loading amount of Ag nanoparticles on the shell layer. P(St-NIPAM)/PNIPAM-Ag composite microgels as a catalyst has excellent perfomance for reduction 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) within 45 min.

Key words: poly(N-isopropylacrylamide), silver nanoparticle, composite microgel, thermosensitivity, 4-nitrophenol reduction