Synthesis, Characterization, and Silver Nanoparticles Fabrication in N-isopropylacrylamide-Based Polymer Microgels for Rapid Degradation of p-Nitrophenol

Abstract

Multiresponsive poly(N-isopropylacrylamide-co-methacrylic acid) microgels were synthesized by precipitation polymerization in aqueous medium. Then silver-poly(N-isopropylacrylamide-co-methacrylic acid) hybrid microgels were prepared by in-situ reduction of silver ions. Formation of microgels was confirmed by Fourier transform infrared spectroscopic analysis. pH and temperature sensitivity of microgel was studied by dynamic light scattering. Hydrodynamic radius of microgels decreases with increase in temperature at pH 8.20 and show volume phase transition temperature around 45°C. At pH 2.65, hydrodynamic radius decreases with increase in temperatures upto 35°C but further increase in temperature causes aggregation and microgel becomes unstable due to increase of hydrophobicity. With increase in pH of medium, the hydrodynamic radius of microgels increases sigmoidally. Formation of silver nanoparticles inside microgel and pH dependence of surface plasmon resonance wavelength of the hybrid microgels were investigated by ultraviolet-visible spectroscopy. The value of surface plasmon resonance band and absorbance associated with surface plasmon resonance band increases with increases in pH of the medium. The apparent rate constant of reduction of p-nitrophenol was found to be linearly dependent on volume of hybrid microgels used as catalyst. The system has a potential to be used as effective catalyst for rapid degradation of industrial pollutant.

Keywords:

• Catalysis
• hybrid gels
• microgels
• pH sensitivity
• surface plasmon resonance
• temperature sensitivity

Acknowledgments

The authors are grateful to the University of the Punjab, Lahore, Pakistan, for financial support under Research Project Grant for the fiscal year 2011–2012.