Preparation And Magnetic Functionalization Of A Series Of Polystyrene Microspheres Based On Seed Swelling Method

Various functional microspheres based on polystyrene（PS）are widely used in chromatographic separation,carrier catalysis,standard metrology,biomedicine,information communication,microelectronics and some high-tech fields because they have the characteristics of small particle size,large specific surface area,easy surface modification,good biocompatibility,high mechanical strength and stable physical and chemical properties.In view of the current international situation that all walks of life are developing rapidly,there is a huge demand for various functional microspheres based on PS at home and abroad.However,the functional PS microspheres used in high-end applications in China basically rely on imports.Domestic substitution of PS functional microspheres used in high-end fields is an important topic in materials science and technology research,and it is also an issue that needs attention from all walks of life.Although many domestic researchers have carried out a lot of corresponding research on the preparation of functional PS microspheres,and have achieved a series of important research results,the mechanism and technical details of the preparation of microspheres still need to be improved.Therefore,the synthesis of functional microspheres has been affected,and the related microspheres preparation technology has become the bottleneck technology in China.Therefore,combined with the growth mechanism of PS microspheres,it is extremely important for the preparation of polystyrene functional microspheres to adjust the synthesis conditions and routes of PS-based microspheres and explore a series of problems such as particle size control,spatial morphology control,and functionalization.Based on the above research background,this paper attempts to explore the preparation of PS microspheres from the perspectives of particle size,structure and functionalization,and strive to prepare PS microspheres with controllable particle size and structure and magnetic functionalization.It is expected to provide some useful experimental results and theoretical explorations for the serial preparation of PS microspheres.The main research are as follows:1.An attempt was made to control the particle size of PS microspheres based on the one-step seed swelling polymerization method.Monodisperse PS microspheres prepared by dispersion polymerization or emulsion polymerization were used as seed microspheres.Monodisperse PS microspheres with different particle sizes were prepared by changing the the particle size and cross-linking degree of seed microspheres,swelling time,swelling temperature,monomer amount and swelling times.The results show that PS microspheres with good monodispersity can be obtained with high efficiency when the swelling temperature is 30°C and the swelling time is 6 h.The particle size of the product PS microspheres can be well controlled by adjusting the particle size of the PS seed microspheres itself and the amount of monomer added during the swelling process.PS microspheres with different morphologies can be obtained by changing the cross-linking degree of the PS seed microspheres.The coefficient of variation of PS microspheres prepared by the one-step seed swelling polymerization method are small,and a series of monodisperse PS microspheres with controllable particle size can be successfully prepared by adjusting the above variables.2.An attempt was made to control the spatial morphology and structure of PS microspheres based on the two-step seed swelling polymerization method.A variety of monodisperse uncrosslinked PS microspheres with different particle sizes and molecular weights were used as seed microspheres.Monodisperse porous PS microspheres with different particle sizes and pore sizes were prepared by changing the type and ratio of porogen,particle size and molecular weight of PS seed microspheres,and the ratio of styrene（St）and divinylbenzene（DVB）.The results show that the closer the solubility parameter of the porogen or co-porogen is to that of the St-DVB copolymer,the smaller the average pore size and the larger the specific surface area of the prepared porous PS microspheres.The increase in particle size of the porous PS microspheres prepared by the two-step seed swelling polymerization method is much larger than that of the one-step seed swelling polymerization method.By continuing to adjust the ratio of porogen or mixed monomer to seed microspheres,monodisperse porous PS microspheres with larger particle size can be obtained.With the increase of the particle size of PS seed microspheres and the decrease of the molecular weight,the specific surface area and pore volume of the prepared porous PS microspheres gradually decreased,and the average pore size increased.The smaller the value of St/DVB,the smaller the average pore size of the porous PS microspheres and the larger the specific surface area.A series of monodisperse porous PS microspheres with controllable pore size can be successfully prepared by adjusting the above-mentioned influencing factors in the two-step seed swelling polymerization method.3.An attempt was made to functionalize the PS-based microspheres obtained before to prepare magnetic microspheres with uniform and controllable particle size,strong magnetism and surface functional modification.A method for preparing magnetic polymer microspheres by miniemulsion polymerization using functionalized porous polymer microspheres as templates was developed.The prepared magnetic polymer microspheres were used to remove cationic dyes in aqueous solution.Porous poly（methyl methacrylate-co-glycidyl methacrylate）（P（MMA-co-GMA））microspheres were prepared based on the above two-step seed swelling polymerization method and hydrolyzed with alkali and acid,respectively.The oleic acid-modified Fe₃O₄ nanoparticles were dispersed in methyl methacrylate（MMA）,divinylbenzene（DVB）,and glycidyl methacrylate（GMA）to form a magnetic fluid.It was swollen into the hydrolyzed porous P（MMA-co-GMA）microspheres and then polymerized to obtain magnetic Fe₃O₄@P（MMA-co-GMA）microspheres.Further considering the characteristics of large specific surface area,easy magnetic separation,and surface functionalization of Fe₃O₄@P（MMA-co-GMA）microspheres,they were used as adsorbents to remove the cationic dye Nile blue from water.The experimental results show that the maximum adsorption capacity of Nile blue by microspheres is 109.4 mg/g,and the maximum dye removal rate can reach 99.9%.In addition,Fe₃O₄@P（MMA-co-GMA）microspheres exhibited good stability and recyclability for Nile blue removal after 7 cycles.The microspheres can not only be used as efficient,durable and sustainable adsorbents for water treatment,but also show great potential application value in many fields.