Investigation on colloidal stability of iron oxide nanoparticles in water based ferrofluid using comb polymeric surfactants

In this research، magnetite iron oxide nanoparticles were synthesized via coprecipitation method and their colloidal stability was investigated using 3 different comb polymeric surfactants based on polyacrylic acid-co-polyethylene glycol acrylate in water media. The difference of these surfactants is in tree type of polyethylene glycol with molecular weights of 1000، 2000 and 4000 which is connected to hydrophobic acrylate chain. The effects of synthesis temperature and time on particle sizes were studied. The temperature and time range was determined 27-90C and 10-40 min، respectively. To synthesis of magnetite nanoparticles، ferric and ferrous chlorides were precipitated with pH adjustment using ammonia (25 wt %) solution. The size distribution and stability of particles were studied via dynamic light scattering (DLS) and turbidimetry، respectively. The attachment of surfactants on nanoparticles was studied using fourier transform infrared spectroscopy (FTIR). Results showed that the particle sizes are different related to molecular weights of polyethylene glycol in comb polymeric surfactants. The com polymeric surfactant with polyethylene glycol Mw=2000 was lead to lower mean particle size and better stability relative to others. Moreover it was revealed that the best magnitude colloidal stability was with 22 wt % from comb polymeric surfactant having polyethylene glycol Mw=2000 at 70C for 20 min. The hydrodynamic size of particles was 80nm in this condition.