Preparation Of Polymeric Particles With Unusual Morphology By Seeded Emulsion Polymerization

The polystyrene (PSt) microspheres were prepared by emulsifier-free emulsion polymerization in this article. The size and size distribution (Dw/Dn) of resulted PSt microsheres were respectively 375nm and 1.0. The effects of the concentration of St and KPS, polymerization temperature and the composition of the solvent on the size and morphology of the PSt microspheres were investigated by scanning electron microscopy (SEM). The best reaction condition was then established.Using the PSt microspheres as the seeds, acrylonitrile (AN) as the second monomer, linear poly(ethylene glycol) (PEG), poly(N-isopropylacrylamide) macromonomer (St-PNIPAAm) with a styrol end group, and PEG macromonomer (MA-PEG) with a methacryloyl end group to synthesize the global PSt/PAN composite particles. The morphology and diameters of the particles were characterized by transmission election microscopy (TEM) and laser lighter scattering (LLS). It showed that the different stabilizers do not greatly affect the morphology of the composite particles. When used AN as the single monomer can't obtain the unusual morphology composite particles with accidented surfaces. The size and size distribution of final particles were gradually reduced by increasing the dosage of MA-PEG. When the dosage of AN increased the size and size distribution of the particles were gradually enhanced.The unusual morphology particles were prepared by seeded emulsion polymerization using specifical ratio of St and AN. The effects of the St monomer concentration, AN monomer concentration, total monomer concentration, the method of adding the monomer and the type of the initiator on the morphology and the size were studied by SEM. It was found that increasing the dosage of St the heave on the surface decreased and the diameter increased, increasing the dosage of AN the heave on the surface increased, the concentration of total monomer plays an important role in the diameter of the particles. Using the method of adding the second monomer when the seeded polymerization didn't finish it was found that the later monomer added the larger of the heave would be. Using different category of the initiator can obtain different morphology particles. The different morphology and diameter composite particles can be obtained by changing the reaction condition of the seeded emulsion polymerization.The morphology of the composite particles prepared by emulsifier-free seeded emulsion polymerization was almost the same as the ones prepared by dispersion copolymerization of St with AN in the presence MA-PEG or St-PEG macromonomer. The result ulteriorly proved formation mechanism of the unusual morphology for dispersion copolymerization system. The composite particles were covered with PEG group on their surface. They could be widely used at biomedicine and biotechnology fields.