Preparation of carboxylic magnetic polymeric composite particles by miniemulsion polymerization in the absence of hydrophobe

Carboxylic magnetic polymeric composite particles (C-MPCPs) were prepared by miniemulsion polymerization in the absence of hydrophobe using styrene (St) as monomer, methacrylic acid (MAA) as comonomer, sodium dodecyl sulfate (SDS) as emulsifier, and azodiisobutyronitrile (AIBN) as initiator in the presence of hydrophobic magnetite particles. For comparison. non-carboxylic magnetic polymeric composite particles (N-MPCPs) were also prepared under the same conditions as C-MPCPs but without MAA as comonomer. Microscopic morphology of resulting C-MPCPs and N-MPCPs was observed by Transmission Electron Microscopy (TEM). Magnetic properties of C-MPCPs in dry condition were investigated by vibrating sample magnetometer (VSM). The results showed that the encapsulation of magnetite to prepare C-MPCPs by miniemulsion in the absence of hydrophobe was successful but not totally successful in the preparation of N-MPCPs, and the resultant C-MPCPs exhibited a broad practical size distribution, superparamagnetism and a certain level of magnetic response. The mechanism of miniemulsion polymerization to encapsulate magnetite particles successfully in the absence of hydrophobes was hypothesized that the hydrophobic magnetite particles could act as a hydrophobe and MAA could enhance the hydrophobicity of magnetite particles by ensuring oleic acid adsorption on magnetite particles' surface in acid form instead of salt form. (C) 2009 Elsevier B.V. All rights reserved.