Synthesis and characterization of hydrophilic polymer nanoparticles using n-isopropylacrylamide (NIPAM) via emulsion polymerization technique

Abstract

Poly(N-isopropylacrylamide) (PNIPAM) nanoparticles were successfully synthesized via emulsion polymerization techniques using different critical micelle concentrations (CMCs) of sodium dodecyl sulphate (SDS) surfactant, temperature and time of polymerization. The effects of surfactant concentrations on emulsion polymerization of PNIPAM nanoparticles have been discussed. Potassium persulfate (KPS) and N,N'-methylenebisacrylamide (MBAA) were used as initiator and cross-linker, respectively throughout the emulsion polymerization. The formation of PNIPAM nanoparticles was confirmed by Fourier transform infrared spectroscopy (FTIR) with absorption peaks observed at 2997 and 2930 cm-1 for C-H stretching of CH3 and CH2 groups, 1459 cm-1 for 2° amide C=O stretch, 3310 cm-1 and 3275 cm-1 for N-H stretching band. The particle size and morphology of PNIPAM nanoparticles were determined using scanning electron microscopy (SEM) where large aggregation of PNIPAM nanoparticles were observed with average diameters in the range of 20 - 50 μm and the appearance of pore structure on the hydrogel surface. Thermal stability of PNIPAM nanoparticles were obtained by thermogravimetric analysis (TGA) where it showed the percentage of mass loss at certain temperature.