| The core-shell structure polymer composite particles with greater size can be applied in solvent adsorption, drug and catalyzer carrier. Although the synthesis of small size core-shell polymer composite particles via the conventional seeded emulsion polymerization and seeded dispersion polymerization has been widely investigated, the preparation of core-shell structure polymer particles with greater size is still a challenging work. Thus, it is necessary to develop a new method for synthesizing the core-shell polymer composite particles with greater size.An original method, named suspension-emulsion combined polymerization (SECP), was proposed to prepare the core-shell polymer particles with the greater size in this thesis. During the SECP process, the emulsion polymerization constituents (EPC) were added to suspension polymerization (SP) system at the different stages of suspension polymerization drop-wisely. The suspension polymerization and emulsion polymerization processes would be combined in chemical reaction and particle formation process, and the core-shell polymer composite particles with greater size would be formed by controlling the polymerization conditions. The influences of polymerization conditions and the properties of second monomer on the particle feature, the particle formation process and mechanism, the composition variation of polymer particles, the kinetic of SECP and the application of SECP were investigated.Firstly, SECP using styrene (St) as the suspension polymerization monomer, and methyl methacrylate (MMA) as the emulsion polymerization monomer, was carried out. It is found that the EPC addition strategy, the constituents of EPC and the features of dispersed droplets in St suspension polymerization system were the key factors affecting the formation of core-shell structure particles, and the EPC addition strategy was the most important factor in the formation of core-shell polymer particles.Secondly, the particle features of the resulting polymer particles and the particle formation mechanism of SECP were studied. It is found that PMMA latex particleswere gradually coagulated with PS particles after the addition of EPC at the mid stage of St suspension polymerization, and core-shell structure PS/PMMA composite particles with greater size were finally formed. St/MMA copolymer particles composed of primary particles and imperfect core-shell structure PS/PMMA composite particles were obtained by adding EPC at the initial and later stage of St SP, respectively. According to the particle formation mechanism of St suspension polymerization and the variations of particle features of PS/PMMA composite particles, the particle formation mechanism of SECP were proposed.The composition of composite polymer particles was analyzed by using FTIR, extraction, [H-NMR and l3C-NMR methods. It is found that the molar ratio of MMA/St units in composite particles increased and the content of PMMA latex particles decreased with the increasing of polymerization time after the addition of EPC. So, it is evidenced that PMMA latex particles would be coagulated with PS suspension particles in SECP and transfer process existed between two kinds of particles after the coagulation. The composite polymer particles were composed of PS, PMMA and MMA-St copolymer.The kinetics study of SECP showed that the addition of MMA EPC had no significant influence on the reaction rate of St suspension polymerization. The kinetics of MMA polymerization was quite different from that of MMA conventional emulsion polymerization due to the aggregation of PMMA latex particles onto the surface of PS suspended particles. The conversion and polymerization rate of MMA in SECP were lower than that of MMA conventional emulsion polymerization at the same conditions. The polymerization rate of MMA in SECP was increased with the increasing of the emulsifier or initiator concentration. The influences of the emulsifier concentration and the initiator concentration on the steady stage polymerization rate (Rp) of MMA in SECP and conventional emulsion polymerization could be related by the following equations: Rp (secp) oc[S]050[I]059andRp(emulsion)°c[S]074[l]030.The influences of the second monomer properties on the morphology of polymer composite particles were investigated. The perfect core-shell polymer particles couldbe formed in a wide conversion range of suspension polymerization when EPC containing monomer with less water solubility and greater solubility with PS was added. The mass ratio of shell/core of polymer particles were greater than that of polymer particles prepared by adding of EPC containing monomer with more water solubility. The PMMA/PS particles were prepared by SECP and the phase inversion was not found in the particles.Finally, SECP process was applied to prepare AAS and PMMA/PHMA core-shell composite particles with great size. AAS resin with a great grafting degree of St and AN, and a greater rubber content could be prepared by adding of EPC of AN and St after the addition of EPC of butyl acrylate in SECP process. The rubber phase was distributed more homogeneously in plastics phase after the melt processing. The mechanical properties of AAS prepared by SECP process were similar to that of AAS resin prepared by seeded emulsion polymerization. The particle morphology, swelling, drug absorption and release properties of PMMA/PHEMA microspheres prepared by SECP were investigated. It is found that the composite microspheres exhibited porous structure in the surface, and PHEMA latex particles were coagulated on the surface of PMMA particle. The swelling ratios of PMMA/PHEMA composite microspheres in water and benzyl alcohol were greater than that of PMMA microspheres. The absorption percentage of ibuprofen on PMMA/PHEMA composite microspheres was 35.6% in 48h, and the equilibrium release time and release percentage of ibuprofen were 360h and 82%, respectively. While, the absorption percentage of ibuprofen on PMMA microspheres was 27.6%, and the equilibrium release time and percentage were 216h and 60%, respectively.
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