Synthesis and characterization of p(NIPAM-AA-AAm) microgels for tuning of optical Properties of silver nanoparticles

Three compositions of p(NIPAM-AA-AAm) terpolymer microgels with various AA content have been prepared by free radical emulsion polymerization. Silver nanoparticles were synthesized in these microgels by in-situ reduction method. The temperature sensitivity of terpolymer microgels and hybrid gels was investigated using dynamic laser light scattering technique at three different pH values. The hydrodynamic radius of the microgels as a function of pH at 20 and 50 degrees C was also studied by the same technique. The optical properties of silver nanoparticles (AgNPs) have been studied by UV-Visible and Photo-luminescence measurements at various conditions of pH and temperature. The pH and temperature sensitivity of microgels was compared with hybrid polymer microgels of the same monomer compositions. The equilibrium swelling ratios, volume phase transition temperature and critical transition pH of microgels and hybrid gels was found to be dependent on microgels composition. A two step volume phase transition was observed with high acrylic acid content in acidic conditions. The terpolymer microgels and hybrid gels become unstable at low pH and high temperature.