SURFACE-MODIFIED POLYMER MICROSPHERES OBTAINED BY THE EMULSION COPOLYMERIZATION OF 2-METHACRYLOYLOXYETHYL PHOSPHORYLCHOLINE WITH VARIOUS VINYL MONOMERS

A series of copolymer microspheres of 2-methacryloyloxyethyl phosphorylcholine (MPC) with comonomers (M) such as methyl-(MMA), ethyl-(EMA), n-butyl-(BMA), hexyl methacrylate (HMA), and styrene (St), poly(MPC-co-M), was prepared from the emulsifier-free emulsion copolymerization. From the kinetics of copolymerization of MPC and MMA, it was found that the initial rate of polymerization of MMA increased drastically in the presence of small amounts of MPC. A decrease in the yield of poly(MPC-co-MMA) microspheres and increase in that of its aggregates were observed with increasing content of the MPC moiety from 0 to 10 mol% in feed. The diameters of poly(MPC-co-M) microspheres were much smaller than those of corresponding poly(M) microspheres except for poly(MMA) microspheres. It was confirmed from XPS measurements that the MPC moiety is localized on the surface of particles. A series of poly(MPC-co-M) microspheres was found to absorb bovine serum albumin (BSA) less than the corresponding poly(M) microspheres as the control. It was concluded that the reduction of adsorbtion of BSA on poly(MPC-co-M) is dependent on the hydrophilicity of comonomer M and the MPC composition on the surface of particles.